Repair mounted Scenario fixtures for qualified owners and inspector tabs

Import unchanged from b8685416f56e53e30bd11ecf93a54cea10ac8458; Git blob f641989214. Required by oa-core/tests/attachment_workshop.rs.

.gitattributes

@@ -15,9 +15,77 @@
 
 # Exact source/recovery oracles and archived ledgers retain their measured bytes.
 # Keep ordinary text diffs; only disable checkout/check-in newline conversion.
+PROJECT_GOAL.md -text whitespace=cr-at-eol
 harness/fixtures/release1-native/** -text
 harness/fixtures/interface-operation-probe/** -text
 harness/history/2026-09-06-ledgers-before-consolidation/** -text
+harness/history/2026-09-10-ledgers-before-continuation-refresh/** -text
+harness/history/2026-09-10-ledgers-before-second-consolidation/** -text whitespace=blank-at-eol,blank-at-eof,space-before-tab,cr-at-eol
+harness/experiments/textual-authoring-20260911-local/** -text whitespace=blank-at-eol,blank-at-eof,space-before-tab,cr-at-eol
 crates/oa-desktop/src/recovery/fixtures/*.json -text
+crates/oa-core/src/analysis_numeric/fixtures/** -text whitespace=cr-at-eol
 harness/fixtures/source7-native/** -text
 harness/fixtures/basic-editing/** -text
+harness/fixtures/scenario-authoring/base/** -text whitespace=cr-at-eol
+harness/experiments/textual-authoring-20260911/** -text whitespace=cr-at-eol
+harness/experiments/textual-authoring-20260911/observed/split-entry.arcadia whitespace=-blank-at-eol,cr-at-eol
+harness/experiments/analysis-context-20260911/** -text whitespace=cr-at-eol
+harness/experiments/analysis-baseline-20260911/** -text whitespace=cr-at-eol
+harness/experiments/library-compatibility-20260911/** -text whitespace=cr-at-eol
+harness/experiments/refined-contracts-review-20260911/** -text whitespace=cr-at-eol
+harness/behavior-creation-contract.rs -text whitespace=cr-at-eol
+harness/experiments/source-cli-independent-20260911/** -text whitespace=cr-at-eol
+harness/experiments/authoring-prerelease-20260911/** -text whitespace=cr-at-eol
+harness/experiments/cli-packaging-20260911/** -text whitespace=cr-at-eol
+harness/experiments/cli-prerelease-20260911/** -text whitespace=cr-at-eol
+harness/experiments/contextual-source-20260911/** -text whitespace=cr-at-eol
+harness/experiments/contextual-source-20260911/**/*.log whitespace=-blank-at-eof,cr-at-eol
+harness/fixtures/staged-source-authoring/** -text whitespace=cr-at-eol
+harness/staged-source-authoring-contract.rs -text whitespace=cr-at-eol
+
+# Preserve checksum-bound font notices verbatim through Git round trips.
+scripts/windows-notices/GNOME-Cantarell-61362600e104-COPYING -text
+scripts/windows-notices/Fira-OFL.txt -text
+scripts/windows-notices/FiraSans-Regular-NOTICE.txt -text
+harness/experiments/behavior-creation-native-20260911/** -text whitespace=cr-at-eol
+harness/experiments/constructor-defaults-20260911/** -text whitespace=cr-at-eol
+harness/experiments/constructor-defaults-20260911/results/*.arcadia whitespace=-blank-at-eol,cr-at-eol
+harness/release-scenario-native-9e8r6t-20260911.md -text whitespace=cr-at-eol
+harness/experiments/analysis-numeric-gate-20260911/** -text
+harness/experiments/chooser-correction-20260911/** -text whitespace=-blank-at-eof,cr-at-eol
+harness/experiments/chooser-lint-gate-20260911/** -text whitespace=-blank-at-eof,cr-at-eol
+harness/history/2026-09-11-behavior-wiki-before-refresh.md -text whitespace=cr-at-eol
+# Preserve the independently fingerprinted historical review verbatim.
+harness/release-behavior-canvas-phase1-review-20260911.md -text whitespace=-blank-at-eof,cr-at-eol
+harness/experiments/scenario-native-3c9e6ee-20260911/** -text whitespace=-blank-at-eof,cr-at-eol
+harness/experiments/scenario-native-3c9e6ee-20260911/**/*.arcadia whitespace=-blank-at-eol,-blank-at-eof,cr-at-eol
+harness/experiments/analysis-codec-windows-20260911/** -text whitespace=-blank-at-eof,cr-at-eol
+harness/history/2026-09-11-ledgers-before-gitea-migration/** -text whitespace=-blank-at-eol,-blank-at-eof,cr-at-eol
+harness/experiments/canvas-union-windows-20260911/** -text whitespace=-blank-at-eof,cr-at-eol
+harness/experiments/canvas-a31b40d-windows-native-20260911/** -text whitespace=-blank-at-eol,-blank-at-eof,cr-at-eol
+harness/experiments/allocation-d9b3f0d-windows-20260912/** -text whitespace=-blank-at-eol,-blank-at-eof,cr-at-eol
+harness/experiments/allocation-3840ca2-pause-20260912/** -text whitespace=-blank-at-eol,-blank-at-eof,cr-at-eol
+harness/experiments/diagram-removal-windows-20260912/** -text whitespace=-blank-at-eol,-blank-at-eof,cr-at-eol
+harness/experiments/diagram-resize-foundation-20260912/** -text whitespace=-blank-at-eol,-blank-at-eof,cr-at-eol
+harness/experiments/delete-native-f7-20260912/** -text whitespace=-blank-at-eol,-blank-at-eof,cr-at-eol
+harness/experiments/canvas-editing-followup-20260912/** -text whitespace=-blank-at-eol,-blank-at-eof,cr-at-eol
+harness/experiments/resize-port-policy-20260912/** -text whitespace=-blank-at-eol,-blank-at-eof,cr-at-eol
+harness/experiments/canvas-native-83f53c7-20260912/** -text whitespace=-blank-at-eol,-blank-at-eof,cr-at-eol
+harness/experiments/nested-lifecycle-union-20260912/** -text whitespace=-blank-at-eol,-blank-at-eof,cr-at-eol
+harness/experiments/canvas-native-d61f1f3-20260912/** -text whitespace=-blank-at-eol,-blank-at-eof,cr-at-eol
+harness/experiments/lifecycle-fixture-preflight-20260913/** -text whitespace=-blank-at-eol,-blank-at-eof,cr-at-eol
+harness/experiments/palette-readability-20260913/** -text whitespace=-blank-at-eol,-blank-at-eof,cr-at-eol
+harness/release-analysis-next-acceptance-20260913.md -text whitespace=-blank-at-eol,-blank-at-eof,cr-at-eol
+harness/experiments/runtime-notices-20260913/** -text whitespace=-blank-at-eol,-blank-at-eof,cr-at-eol
+harness/experiments/analysis-checked-save-windows-20260913/** -text whitespace=-blank-at-eol,-blank-at-eof,cr-at-eol
+harness/experiments/canvas-native-dd39e1f-20260913/** -text whitespace=-blank-at-eol,-blank-at-eof,cr-at-eol
+harness/experiments/navigation-palette-e124029-windows-20260913/** -text whitespace=-blank-at-eol,-blank-at-eof,cr-at-eol
+harness/experiments/navigation-native-preparation-e124029-20260913/** -text whitespace=-blank-at-eol,-blank-at-eof,cr-at-eol
+harness/experiments/analysis-source-s0-s1-windows-20260913/** -text whitespace=-blank-at-eol,-blank-at-eof,cr-at-eol
+harness/experiments/analysis-source3-bridge-windows-20260913/** -text whitespace=-blank-at-eol,-blank-at-eof,cr-at-eol
+harness/scenario-analysis-version-integration-review-20260913.md -text whitespace=cr-at-eol
+harness/scenario-analysis-version-integration-inputs-20260913.json -text whitespace=cr-at-eol
+harness/experiments/analysis-source-s2a-windows-20260913/** -text whitespace=-blank-at-eol,-blank-at-eof,cr-at-eol
+
+# Preserve the pinned Iced dependency bytes and upstream manifest.
+crates/vendor/iced_widget/** -text whitespace=cr-at-eol

.gitignore

@@ -11,3 +11,4 @@
 /model-store/
 /.local/
 .arcadia-save-*/
+__pycache__/

Cargo.lock

@@ -1567,8 +1567,6 @@ dependencies = [
 [[package]]
 name = "iced_widget"
 version = "0.14.2"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "b1596afa0d3109c2618e8bc12bae6c11d3064df8f95c42dfce570397dbe957ab"
 dependencies = [
  "iced_renderer",
  "log",
@@ -2107,6 +2105,25 @@ dependencies = [
  "jni-sys 0.3.1",
 ]
 
+[[package]]
+name = "num-bigint"
+version = "0.5.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "93e7820bc0a80a0238e650327316f929ba18d5be054b647490a3a6a339f3e7c0"
+dependencies = [
+ "num-integer",
+ "num-traits",
+]
+
+[[package]]
+name = "num-integer"
+version = "0.1.47"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "7ce2d95d4b3734dc35aa2f45e1aa22cd416814592a4f9d9205e11affd5b8e10b"
+dependencies = [
+ "num-traits",
+]
+
 [[package]]
 name = "num-traits"
 version = "0.2.19"
@@ -2139,11 +2156,23 @@ dependencies = [
  "syn 2.0.119",
 ]
 
+[[package]]
+name = "oa-cli"
+version = "0.2.0"
+dependencies = [
+ "oa-core",
+ "serde",
+ "serde_json",
+]
+
 [[package]]
 name = "oa-core"
 version = "0.2.0"
 dependencies = [
  "libc",
+ "num-bigint",
+ "num-integer",
+ "num-traits",
  "same-file",
  "serde",
  "serde_json",
@@ -2167,6 +2196,7 @@ dependencies = [
  "serde_json",
  "tempfile",
  "tokio",
+ "unicode-segmentation",
 ]
 
 [[package]]

Cargo.toml

@@ -1,7 +1,11 @@
 [workspace]
-members = ["crates/oa-core", "crates/oa-desktop", "crates/oa-server"]
+members = ["crates/oa-core", "crates/oa-desktop", "crates/oa-server", "crates/oa-cli"]
+exclude = ["crates/vendor/iced_widget"]
 resolver = "2"
 
+[patch.crates-io]
+iced_widget = { path = "crates/vendor/iced_widget" }
+
 [workspace.package]
 version = "0.2.0"
 edition = "2024"

README.md

@@ -18,12 +18,14 @@ From the repository root:
 cargo run --locked -p oa-desktop --bin arcadia-studio
 ```
 
-Build both desktop and server release executables:
+Build the desktop, server and source CLI release executables:
 
 ```sh
 cargo build --release --workspace --locked
 ```
 
+Stage the complete teaching examples beside these executables so **Home → Open water-pressure walkthrough** works in an optimized source build. From the repository root, use `Copy-Item -Recurse -Force examples target/release/` in PowerShell or `cp -R examples target/release/` on Linux. If you set a different Cargo target directory or pass `--target`, use that build's executable directory instead of `target/release`. The packaging scripts include these examples automatically.
+
 Run `target/release/arcadia-studio.exe` on Windows or `./target/release/arcadia-studio` on Linux. No task-specific cache directory is required. A graphical desktop and compatible graphics driver are required; the application uses Iced 0.14 with WGPU and X11/Wayland support. It does not require Java, Eclipse, a browser, an account or a running server.
 
 An optional Windows path uses the `stable-x86_64-pc-windows-gnullvm` Rust toolchain with LLVM-MinGW. Put LLVM-MinGW's `bin` directory on `PATH`, including `clang.exe` and `llvm-windres.exe`, then run:
@@ -49,17 +51,34 @@ The earlier V2 package record describes `dist/ArcadiaStudio-Windows.zip` and `di
 
 The current [Windows packaging instructions](docs/windows-packaging.md) stage both executables, verify their runtime DLL dependencies, and produce an archive with checksums and provenance. Native acceptance fixtures and independent expected results are retained in [the release fixture directory](harness/fixtures/release1-native/README.md).
 
+## Work with source files from the command line
+
+The `arcadia` CLI checks an explicit `.arcadia` entry file and its includes without
+starting the desktop or server:
+
+```sh
+cargo run --locked -p oa-cli --bin arcadia -- check examples/text-first/project.arcadia
+```
+
+`stabilize ROOT` previews the identities needed for persistent editing;
+`rename-alias ROOT OLD NEW` previews an alias change and its references. Add
+`--write` to save that invocation's candidate, or `--json` for structured
+diagnostics and changed-file text/diffs. Preview leaves files untouched.
+See [source CLI commands](docs/source-cli.md) for examples and exit codes.
+
 ## Model operational needs and system responsibilities
 
 The desktop starts at **Home**, where you can create a model, open a local project, continue recent files or recover retained work. Missing recent files stay visible with **Locate**; **Remove** only forgets their history entry. Choose **Explore rescue example** for a model combining people, an organization, a System of Interest, information and physical exchange items, normal/degraded behavior and code/CAD evidence.
 
 The example opens in an architecture view with work nested inside its performers. Each layer also has dedicated functional dataflow and mission/capability views. Regenerate both example formats with matching identities using `cargo run --locked -p oa-core --example generate_demo`; the command verifies both saved models. Historical migration fixtures remain separate.
 
+The architecture diagram has a compact side palette; expand it to see tool names. Choose an element tool, click its position, enter its name in place and press **Enter**. **Escape** cancels the draft. Select a card and press **F2** to rename it. Right-click a participant and choose **Add activity** or **Add function** to create work with its performer allocation in one undoable edit. Ordinary palette creation leaves work unallocated. **Add existing** places a compatible model element in the current view; **Include already shown** offers **Locate** for existing placements.
+
 1. In **Operational Analysis**, create entities, actors, activities and capabilities. Use **In selected** for semantic decomposition and **Allocated** for new leaf work performed by a participant. Activities can decompose independently of their performer; roles capture shared operational responsibility. **Communication means** connects operational Entities or Actors directly, with direction and carried items; **Exchange allocation** associates the Interactions it carries. Operational communication requires no system ports.
 2. Switch to **System Analysis**. Define one System of Interest and external Actors, then functions, missions, capabilities and functional chains. The system boundary has no internal LA/PA components in this version.
 3. Select a System or System Actor and choose **Add port** in the browser or Properties. Choose Standard or Flow, then **Create port**. Use **Boundary exchange** in the diagram palette, or **Draw boundary exchange** on a selected visible source port, to connect compatible component ports directly. Create the other participant's matching port first if none exists. Functions expose separate input/output port actions; the **Functional exchange** palette tool connects them. **Actions** exposes other engineering relationships and off-diagram configuration; **Data & interfaces** holds reusable payloads and contracts.
 4. Create focused views. **Containment** nests semantic children; **Architecture · allocated work** nests work within performers; **Functional dataflow** shows work decomposition and exchanges; **Missions & capabilities** shows objectives and participation. Dashed, italic parent work denotes an allocation summary inferred from its leaves. Ports appear on their owner's boundary. **View properties** stages saved line-kind, category, behavior-coverage, context, label and individual-hide choices. Right-click empty diagram space for **Duplicate view**, retaining the same semantic records in an independent presentation. Placement **Hide** removes a placement; line hiding retains its relationship; **Delete from model** removes semantics and dependent references.
-5. In **Behavior & scenarios**, author processes/chains, scenario lifelines and ordered occurrences, including repeated uses of the same exchange and explicit fragments/branches. Select a State machine and choose **Create diagram** to place its existing regions and states/modes in a saved view. State machines also support availability and state-action links. Conditions are descriptive, not executable simulation code. Behavior and Data authoring preserve your other diagram layouts.
+5. In **Behavior & scenarios**, choose **New**, select Operational process (OA), Functional chain (SA), Scenario or State machine, then enter its name. For a scenario, choose what its lifelines represent; **Add optional context…** links a context without changing its layer-root ownership. For a state machine, search for its existing participant owner; optionally select **Create the first state view**. Choose **Create and open** to start authoring work contributions, lifelines, ordered occurrences or states. **Cancel · Esc** discards the creation draft; if another dialog is open, Escape dismisses that dialog first. Creation and its optional first view form one Undo operation. A new state machine starts without regions or states; **Create diagram** can later place its existing contents in a saved view. Behavior supports repeated exchanges, fragments/branches, availability and state-action links. Conditions are descriptive, not executable simulation code. Behavior and Data authoring preserve your other diagram layouts.
 6. Select an OA or SA element and choose **Create / update counterpart**. Review dependency scope and counterpart choices, then apply one undoable transaction. For an existing trace, **Review semantics…** compares typed content and prior observations, with explicit keep, take or final-value decisions for supported structural, scalar, constructor, individual-row and ordered-collection changes. Open additional trace rows and choose **Include this row** to combine reviewed source contributions into one validated Apply/Undo transaction; conflicting decisions require resolution. Review does not automatically synchronize the perspectives. **Attachments** reviews an existing child’s parent or a relationship endpoint. **Artifact links** reviews metadata, owner moves, explicit source-absence deletion and creation of a reserved counterpart after all introduced metadata is reviewed. These controls have automated coverage; their native acceptance remains pending. Manual traces link other engineering correspondences. **Traceability** also edits artifact URI, revision and fragment metadata.
 7. Review **Model checks**, then save `.arcadia` source or `.json`. Warnings allow incomplete authoring; structural errors preserve the committed model and rejected draft.
 
@@ -83,6 +102,8 @@ In the state view, **Select / move** drags vertices and containers without repar
 
 ## Edit the same model as text
 
+For a short text-only start, open [the distress-response model](examples/text-first/project.arcadia) and follow [its three-step walkthrough](examples/text-first/README.md). Four declarations and three explicit relationships describe participants, work, responsibility and an exchange; no diagram or handwritten UUID is needed.
+
 **Textual model** has a source-file folder tree, per-file drafts, syntax highlighting, live linting and explicit **Apply all**. Collapse/Locate navigate the hierarchy; collapsed folders retain draft and diagnostic indicators. Right-click a file for contextual actions. Projects can use relative includes to organize source into files. For example:
 
 ```text

crates/oa-cli/Cargo.toml

@@ -0,0 +1,15 @@
+[package]
+name = "oa-cli"
+version.workspace = true
+edition.workspace = true
+license.workspace = true
+rust-version.workspace = true
+
+[[bin]]
+name = "arcadia"
+path = "src/main.rs"
+
+[dependencies]
+oa-core = { path = "../oa-core" }
+serde.workspace = true
+serde_json.workspace = true

crates/oa-cli/src/lib.rs

@@ -0,0 +1,451 @@
+//! Source-only authoring. Preparation captures bytes; only core owns disk writes.
+use oa_core::{
+    Command, language,
+    persistence::MigrationReport,
+    prepare_command,
+    source_files::{self, DiskProject, SourceFileError},
+    source_project::{self, CompiledSourceProject, ProjectLimits, SourceDiagnostic},
+    validation::Severity,
+};
+use serde::Serialize;
+use std::path::{Path, PathBuf};
+
+pub const LIMITS: ProjectLimits = ProjectLimits {
+    max_files: 256,
+    max_include_depth: 32,
+    max_include_edges: 1024,
+    model: language::ParseLimits {
+        max_source_bytes: 64 * 1024 * 1024,
+        max_graph_objects: 100_000,
+        max_records: 250_000,
+        max_step_references: 500_000,
+    },
+};
+
+#[derive(Debug, Clone)]
+pub enum Operation {
+    Check,
+    Stabilize,
+    RenameAlias { old: String, new: String },
+}
+
+#[derive(Debug, Clone, Serialize)]
+pub struct Location {
+    pub path: String,
+    /// Half-open UTF-8 byte offsets. Line/column are one-based Unicode scalars.
+    pub start: usize,
+    pub end: usize,
+    pub line: Option<usize>,
+    pub column: Option<usize>,
+}
+
+#[derive(Debug, Clone, Serialize)]
+pub struct Diagnostic {
+    pub severity: String,
+    pub code: String,
+    pub message: String,
+    pub coordinate_space: String,
+    pub location: Option<Location>,
+    pub related: Vec<Location>,
+    pub object_id: Option<String>,
+    pub field: Option<String>,
+}
+
+#[derive(Debug, Clone, Serialize)]
+pub struct Change {
+    pub path: String,
+    /// Exact captured and proposed UTF-8 text, including line endings.
+    pub before: String,
+    pub after: String,
+    pub diff: String,
+}
+
+#[derive(Debug, Clone, Serialize)]
+pub struct Report {
+    pub format_version: u32,
+    pub entry: String,
+    pub operation: String,
+    pub status: String,
+    pub exit_code: u8,
+    /// True only after a successful changed save. False on failure does not
+    /// promise rollback: consult the specific error/recovery outcome.
+    pub written: bool,
+    pub diagnostics: Vec<Diagnostic>,
+    pub changes: Vec<Change>,
+    pub identities_to_stabilize: usize,
+    pub migration: Option<MigrationReport>,
+    pub notes: Vec<String>,
+}
+
+impl Report {
+    pub fn failure(
+        entry: &Path,
+        operation: &str,
+        exit_code: u8,
+        code: &str,
+        message: String,
+    ) -> Self {
+        let mut report = Self::empty(entry, operation);
+        report.fail(exit_code, code, message);
+        report
+    }
+
+    fn empty(entry: &Path, operation: &str) -> Self {
+        Self {
+            format_version: 1,
+            entry: entry.to_string_lossy().into_owned(),
+            operation: operation.into(),
+            status: "checked".into(),
+            exit_code: 0,
+            written: false,
+            diagnostics: vec![],
+            changes: vec![],
+            identities_to_stabilize: 0,
+            migration: None,
+            notes: vec![],
+        }
+    }
+
+    fn fail(&mut self, exit_code: u8, code: &str, message: String) {
+        self.status = "rejected".into();
+        self.exit_code = exit_code;
+        self.diagnostics.push(Diagnostic {
+            severity: "error".into(),
+            code: code.into(),
+            message,
+            coordinate_space: "operation".into(),
+            location: None,
+            related: vec![],
+            object_id: None,
+            field: None,
+        });
+    }
+}
+
+fn located(issue: SourceDiagnostic, space: &str) -> Diagnostic {
+    let d = issue.diagnostic;
+    Diagnostic {
+        severity: match d.severity {
+            Severity::Error => "error",
+            Severity::Warning => "warning",
+        }
+        .into(),
+        code: d.code,
+        message: d.message,
+        coordinate_space: space.into(),
+        location: Some(Location {
+            path: issue.path,
+            start: d.span.start,
+            end: d.span.end,
+            line: Some(d.line),
+            column: Some(d.column),
+        }),
+        related: issue
+            .related
+            .into_iter()
+            .map(|at| Location {
+                path: at.path,
+                start: at.span.start,
+                end: at.span.end,
+                line: None,
+                column: None,
+            })
+            .collect(),
+        object_id: d.object_id.map(|id| id.to_string()),
+        field: d.field,
+    }
+}
+
+fn disk_error(report: &mut Report, error: SourceFileError) {
+    let code = match &error {
+        SourceFileError::Conflict(_) => "external_change",
+        SourceFileError::RecoveryRequired(_) => "recovery_required",
+        SourceFileError::RecoveryFailed { .. } => "recovery_failed",
+        SourceFileError::Path(_) => "unsafe_path",
+        SourceFileError::Limit(_) => "source_limit",
+        SourceFileError::UnknownExpectation(_) => "unknown_disk_expectation",
+        SourceFileError::Invalid(_) => "invalid_save_candidate",
+        SourceFileError::Io { .. } => "io_error",
+    };
+    report.fail(3, code, error.to_string());
+}
+
+/// A candidate owns its original expectations and is consumed by saving.
+/// Callers cannot replace its source/model/expectations after preparation.
+pub struct Prepared {
+    report: Report,
+    snapshot: DiskProject,
+    compiled: CompiledSourceProject,
+    mutable: bool,
+}
+
+impl Prepared {
+    pub fn report(&self) -> &Report {
+        &self.report
+    }
+
+    pub fn into_report(self) -> Report {
+        self.report
+    }
+
+    pub fn write(mut self) -> Report {
+        if !self.mutable {
+            self.report
+                .fail(2, "usage", "check/lint does not accept --write".into());
+            return self.report;
+        }
+        match source_files::save_project(&self.snapshot, &self.compiled, LIMITS) {
+            Ok(_) => {
+                self.report.written = !self.report.changes.is_empty();
+                self.report.status = if self.report.written {
+                    "written"
+                } else {
+                    "unchanged"
+                }
+                .into();
+            }
+            Err(error) => disk_error(&mut self.report, error),
+        }
+        self.report
+    }
+}
+
+pub fn prepare(entry: &Path, operation: Operation) -> Result<Prepared, Box<Report>> {
+    let name = match operation {
+        Operation::Check => "check",
+        Operation::Stabilize => "stabilize",
+        Operation::RenameAlias { .. } => "rename-alias",
+    };
+    let mut report = Report::empty(entry, name);
+    let snapshot = source_files::load_project(entry, LIMITS).map_err(|error| {
+        disk_error(&mut report, error);
+        Box::new(report.clone())
+    })?;
+    let raw = snapshot.reachable_bundle();
+    // Keep discovery/IO failures that lint cannot recover from the bundle alone.
+    // Recompute source diagnostics below, against the same original bytes.
+    let mut diagnostics: Vec<_> = snapshot
+        .diagnostics
+        .iter()
+        .filter(|d| {
+            matches!(
+                d.diagnostic.code.as_str(),
+                "pending_save"
+                    | "source_encoding"
+                    | "source_limit"
+                    | "invalid_path"
+                    | "missing_include"
+                    | "project_limit"
+            )
+        })
+        .cloned()
+        .collect();
+    for diagnostic in source_project::lint_bundle(&raw, LIMITS) {
+        if !diagnostics.contains(&diagnostic) {
+            diagnostics.push(diagnostic);
+        }
+    }
+    let disk_refusal = snapshot.diagnostics.iter().any(|d| {
+        matches!(
+            d.diagnostic.code.as_str(),
+            "pending_save" | "missing_include" | "invalid_path"
+        )
+    });
+    let invalid = diagnostics
+        .iter()
+        .any(|d| d.diagnostic.severity == Severity::Error);
+    report.diagnostics = diagnostics
+        .into_iter()
+        .map(|d| located(d, "input"))
+        .collect();
+    if invalid {
+        // Do not run declaration analysis or any updater on invalid raw text.
+        // Failed lint may also have allocated provisional object identities.
+        for diagnostic in &mut report.diagnostics {
+            diagnostic.object_id = None;
+        }
+        report.status = "invalid".into();
+        report.exit_code = if disk_refusal { 3 } else { 1 };
+        return Err(Box::new(report));
+    }
+    let explicit_ids: std::collections::BTreeSet<_> = raw
+        .files
+        .values()
+        .flat_map(|text| language::analyze(text).declarations)
+        .filter_map(|d| d.id.map(|id| id.to_string()))
+        .collect();
+    for diagnostic in &mut report.diagnostics {
+        if diagnostic
+            .object_id
+            .as_ref()
+            .is_some_and(|id| !explicit_ids.contains(id))
+        {
+            diagnostic.object_id = None;
+        }
+    }
+    let mut compiled = source_project::compile_bundle(&raw, LIMITS).map_err(|diagnostics| {
+        report.status = "invalid".into();
+        report.exit_code = 1;
+        report
+            .diagnostics
+            .extend(diagnostics.into_iter().map(|d| located(d, "candidate")));
+        Box::new(report.clone())
+    })?;
+    report.identities_to_stabilize = raw
+        .files
+        .values()
+        .map(|text| {
+            language::analyze(text)
+                .declarations
+                .into_iter()
+                .filter(|d| d.id.is_none())
+                .count()
+        })
+        .sum();
+    report.migration = compiled.decoded.migration.clone();
+    let mutable = !matches!(operation, Operation::Check);
+    if let Operation::RenameAlias { old, new } = operation {
+        let project = &compiled.decoded.project;
+        let Some((id, _)) = project
+            .identities()
+            .into_iter()
+            .find(|(_, alias)| *alias == old)
+        else {
+            report.fail(
+                1,
+                "unknown_alias",
+                format!("No declaration has alias '{old}'."),
+            );
+            return Err(Box::new(report));
+        };
+        let command = prepare_command(project, &Command::SetAlias(id, new)).map_err(|error| {
+            report.fail(1, "semantic_command_rejected", error.to_string());
+            Box::new(report.clone())
+        })?;
+        compiled = source_project::update_bundle_with_identity_map(
+            &compiled,
+            &command.project,
+            &command.identity_map,
+            LIMITS,
+        )
+        .map_err(|diagnostics| {
+            report.status = "invalid".into();
+            report.exit_code = 1;
+            report
+                .diagnostics
+                .extend(diagnostics.into_iter().map(|d| located(d, "candidate")));
+            Box::new(report.clone())
+        })?;
+    }
+    if mutable {
+        for (path, after) in &compiled.bundle.files {
+            let before = raw.files.get(path).cloned().unwrap_or_default();
+            if &before != after {
+                report.changes.push(Change {
+                    path: path.clone(),
+                    diff: unified_diff(path, &before, after),
+                    before,
+                    after: after.clone(),
+                });
+            }
+        }
+        report.status = "preview".into();
+        report.notes.push("This invocation's complete proposed changed-file texts and diffs are reported. Without --write nothing is saved; a later invocation may allocate different missing UUIDs. This is not a saved plan or a digest of unchanged dependencies.".into());
+    }
+    report.notes.push("Diagnostic object IDs are omitted for declarations without authored IDs; lint's temporary identities are not the candidate's identities.".into());
+    report.notes.push("Disk writes use the core journal/conflict checks. This is not cross-process atomic visibility or a power-loss durability guarantee; pending saves are never implicitly recovered. A failed write may require explicit journal recovery.".into());
+    Ok(Prepared {
+        report,
+        snapshot,
+        compiled,
+        mutable,
+    })
+}
+
+/// One bounded hunk per file: common prefix/suffix plus three context lines.
+/// Linear in input size; no quadratic LCS allocation for large modules.
+fn unified_diff(path: &str, before: &str, after: &str) -> String {
+    let a: Vec<_> = before.split_inclusive('\n').collect();
+    let b: Vec<_> = after.split_inclusive('\n').collect();
+    let prefix = a.iter().zip(&b).take_while(|(a, b)| a == b).count();
+    let suffix = a[prefix..]
+        .iter()
+        .rev()
+        .zip(b[prefix..].iter().rev())
+        .take_while(|(a, b)| a == b)
+        .count();
+    let start = prefix.saturating_sub(3);
+    let a_end = (a.len() - suffix + 3).min(a.len());
+    let b_end = (b.len() - suffix + 3).min(b.len());
+    let a_start = if a_end == start { start } else { start + 1 };
+    let b_start = if b_end == start { start } else { start + 1 };
+    let mut out = format!(
+        "--- a/{path}\n+++ b/{path}\n@@ -{a_start},{} +{b_start},{} @@\n",
+        a_end - start,
+        b_end - start
+    );
+    let mut emit = |prefix: char, line: &str| {
+        out.push(prefix);
+        out.push_str(line);
+        if !line.ends_with('\n') {
+            out.push_str("\n\\ No newline at end of file\n");
+        }
+    };
+    for line in &a[start..prefix] {
+        emit(' ', line);
+    }
+    for line in &a[prefix..a.len() - suffix] {
+        emit('-', line);
+    }
+    for line in &b[prefix..b.len() - suffix] {
+        emit('+', line);
+    }
+    for line in &a[a.len() - suffix..a_end] {
+        emit(' ', line);
+    }
+    out
+}
+
+pub struct Arguments {
+    pub entry: PathBuf,
+    pub operation: Operation,
+    pub write: bool,
+    pub json: bool,
+}
+
+pub const HELP: &str = "arcadia check ROOT [--json]\narcadia lint ROOT [--json]\narcadia stabilize ROOT [--write] [--json]\narcadia rename-alias ROOT OLD NEW [--write] [--json]\n\nROOT is an explicit .arcadia entry file; includes resolve relative to it.\nMutation commands preview by default. --write applies this invocation's candidate.\nMissing UUIDs in a preview are provisional until written. No canonical formatting.\nExit: 0 valid/success (engineering warnings allowed), 1 invalid source or semantic\ncommand rejection, 2 usage, 3 disk/path/conflict/pending-journal/output failure.\nNo implicit journal recovery. Limits: 64 MiB, 256 files, include depth32/edges1024,\n100000 graph objects, 250000 records, 500000 ordered references.\n";
+
+pub fn arguments(args: &[std::ffi::OsString]) -> Result<Arguments, String> {
+    let mut positional = Vec::new();
+    let (mut write, mut json) = (false, false);
+    for arg in args {
+        if arg == "--write" && !write {
+            write = true;
+        } else if arg == "--json" && !json {
+            json = true;
+        } else if arg.to_string_lossy().starts_with('-') {
+            return Err(format!(
+                "Unknown or repeated option: {}",
+                arg.to_string_lossy()
+            ));
+        } else {
+            positional.push(arg);
+        }
+    }
+    let command = positional.first().and_then(|s| s.to_str()).unwrap_or("");
+    let operation = match (command, positional.len()) {
+        ("check" | "lint", 2) if !write => Operation::Check,
+        ("stabilize", 2) => Operation::Stabilize,
+        ("rename-alias", 4) => Operation::RenameAlias {
+            old: positional[2].to_str().ok_or("Alias must be UTF-8")?.into(),
+            new: positional[3].to_str().ok_or("Alias must be UTF-8")?.into(),
+        },
+        _ => return Err(HELP.into()),
+    };
+    Ok(Arguments {
+        entry: PathBuf::from(positional[1]),
+        operation,
+        write,
+        json,
+    })
+}

crates/oa-cli/src/main.rs

@@ -0,0 +1,102 @@
+use oa_cli::{Report, arguments, prepare};
+use std::{
+    io::{self, Write},
+    path::Path,
+    process::ExitCode,
+};
+
+fn human_report(report: &Report, show_diff: bool) -> io::Result<()> {
+    let mut err = io::stderr().lock();
+    for d in &report.diagnostics {
+        let at = d
+            .location
+            .as_ref()
+            .map(|l| {
+                format!(
+                    "{}:{}:{}",
+                    l.path,
+                    l.line.unwrap_or(0),
+                    l.column.unwrap_or(0)
+                )
+            })
+            .unwrap_or_else(|| report.entry.clone());
+        writeln!(
+            err,
+            "{at}: {}[{}] ({}): {}",
+            d.severity, d.code, d.coordinate_space, d.message
+        )?;
+    }
+    writeln!(
+        err,
+        "{}: {} file changes; {} identities to stabilize",
+        report.status,
+        report.changes.len(),
+        report.identities_to_stabilize
+    )?;
+    if let Some(migration) = &report.migration {
+        writeln!(
+            err,
+            "Source migration: schema {} → {} (separate from identity stabilization)",
+            migration.from_schema, migration.to_schema
+        )?;
+    }
+    for note in &report.notes {
+        writeln!(err, "{note}")?;
+    }
+    if show_diff {
+        let mut out = io::stdout().lock();
+        for change in &report.changes {
+            write!(out, "{}", change.diff)?;
+        }
+        out.flush()?;
+    }
+    err.flush()
+}
+
+fn run() -> io::Result<u8> {
+    let args: Vec<_> = std::env::args_os().skip(1).collect();
+    if args.len() == 1 && (args[0] == "--help" || args[0] == "-h") {
+        io::stdout().write_all(oa_cli::HELP.as_bytes())?;
+        return Ok(0);
+    }
+    if args.len() == 1 && args[0] == "--version" {
+        writeln!(io::stdout(), "arcadia {}", env!("CARGO_PKG_VERSION"))?;
+        return Ok(0);
+    }
+    let json = args.iter().any(|a| a == "--json");
+    let mut displayed = false;
+    let report = match arguments(&args) {
+        Err(error) => Report::failure(Path::new(""), "usage", 2, "usage", error),
+        Ok(args) => match prepare(&args.entry, args.operation) {
+            Err(report) => *report,
+            Ok(prepared) => {
+                if args.write {
+                    if !args.json {
+                        human_report(prepared.report(), true)?;
+                        displayed = true;
+                    }
+                    prepared.write()
+                } else {
+                    prepared.into_report()
+                }
+            }
+        },
+    };
+    if json {
+        serde_json::to_writer_pretty(io::stdout().lock(), &report)?;
+        writeln!(io::stdout())?;
+    } else {
+        human_report(&report, !displayed)?;
+    }
+    Ok(report.exit_code)
+}
+
+fn main() -> ExitCode {
+    match run() {
+        Ok(code) => ExitCode::from(code),
+        Err(error) => {
+            let _ = writeln!(io::stderr(), "Output failed: {error}");
+            ExitCode::from(3)
+        }
+    }
+}

crates/oa-cli/tests/source_cli.rs

@@ -0,0 +1,425 @@
+use oa_cli::{LIMITS, Operation, Prepared, prepare};
+use oa_core::{Id, Project, source_files, source_project};
+use serde_json::Value;
+use std::{
+    collections::BTreeMap,
+    fs,
+    path::{Path, PathBuf},
+    process::Command,
+};
+
+struct Fixture(PathBuf);
+impl Fixture {
+    fn new() -> Self {
+        let path = std::env::temp_dir().join(format!("arcadia-cli-test-{}", Id::new_v4()));
+        fs::create_dir(&path).unwrap();
+        Self(path)
+    }
+    fn put(&self, name: &str, text: &str) {
+        let path = self.0.join(name);
+        fs::create_dir_all(path.parent().unwrap()).unwrap();
+        fs::write(path, text).unwrap();
+    }
+    fn entry(&self) -> PathBuf {
+        self.0.join("project.arcadia")
+    }
+    fn read(&self, name: &str) -> String {
+        fs::read_to_string(self.0.join(name)).unwrap()
+    }
+    fn prepare(&self, op: Operation) -> Prepared {
+        prepare(&self.entry(), op).unwrap_or_else(|report| panic!("{report:#?}"))
+    }
+    fn model(&self) -> Project {
+        let disk = source_files::load_project(&self.entry(), LIMITS).unwrap();
+        source_project::compile_bundle(&disk.reachable_bundle(), LIMITS)
+            .unwrap()
+            .decoded
+            .project
+    }
+    fn cli(&self, args: &[&str]) -> (i32, Value) {
+        let mut command = Command::new(env!("CARGO_BIN_EXE_arcadia"));
+        command
+            .arg(args[0])
+            .arg(self.entry())
+            .args(&args[1..])
+            .arg("--json");
+        let output = command.output().unwrap();
+        assert!(
+            output.stderr.is_empty(),
+            "{}",
+            String::from_utf8_lossy(&output.stderr)
+        );
+        (
+            output.status.code().unwrap(),
+            serde_json::from_slice(&output.stdout).unwrap(),
+        )
+    }
+}
+impl Drop for Fixture {
+    fn drop(&mut self) {
+        let _ = fs::remove_dir_all(&self.0);
+    }
+}
+
+const SIMPLE: &str = "// 雨: authored defaults stay omitted\r\narcadia 7;\r\nproject rescue \"Rescue\" {\r\n    oa_entity team \"Team\" {}\r\n}\r\n";
+
+#[test]
+fn complete_alarm_example_preview_then_write_and_fixed_point() {
+    let fixture = Fixture::new();
+    let source = include_str!(
+        "../../../harness/experiments/textual-authoring-20260911/alarm-response.arcadia"
+    );
+    fixture.put("project.arcadia", source);
+    let (code, check) = fixture.cli(&["check"]);
+    assert_eq!(code, 0);
+    assert_eq!(check["diagnostics"], serde_json::json!([]));
+    let (code, preview) = fixture.cli(&["stabilize"]);
+    assert_eq!(code, 0);
+    assert_eq!(preview["identities_to_stabilize"], 40);
+    assert_eq!(preview["status"], "preview");
+    assert_eq!(fixture.read("project.arcadia"), source);
+    assert!(
+        preview["changes"][0]["diff"]
+            .as_str()
+            .unwrap()
+            .contains("+project alarm_response")
+    );
+    let (code, written) = fixture.cli(&["stabilize", "--write"]);
+    assert_eq!(code, 0);
+    let saved = fixture.read("project.arcadia");
+    assert_eq!(written["changes"][0]["after"], saved);
+    let project = fixture.model();
+    assert_eq!(project.identities().len(), 40);
+    let mut stripped = saved.clone();
+    for (id, _) in project.identities() {
+        stripped = stripped.replace(&format!(" id \"{id}\""), "");
+    }
+    assert_eq!(stripped, source, "only identity clauses may be inserted");
+    let (code, again) = fixture.cli(&["stabilize", "--write"]);
+    assert_eq!(code, 0);
+    assert_eq!(again["changes"], serde_json::json!([]));
+    assert_eq!(again["status"], "unchanged");
+    assert_eq!(fixture.model(), project);
+    assert_eq!(fixture.read("project.arcadia"), saved);
+}
+
+#[test]
+fn captured_candidate_exact_write_preserves_crlf_comments_and_noop_metadata() {
+    let fixture = Fixture::new();
+    fixture.put("project.arcadia", SIMPLE);
+    let candidate = fixture.prepare(Operation::Stabilize);
+    let expected = candidate.report().changes[0].after.clone();
+    assert_eq!(candidate.report().identities_to_stabilize, 2);
+    assert_eq!(fixture.read("project.arcadia"), SIMPLE);
+    assert_eq!(candidate.write().exit_code, 0);
+    assert_eq!(fixture.read("project.arcadia"), expected);
+    assert!(expected.contains("// 雨: authored defaults stay omitted\r\n"));
+    assert!(!expected.contains("description"));
+    let metadata = fs::metadata(fixture.entry()).unwrap().modified().unwrap();
+    let report = fixture.prepare(Operation::Stabilize).write();
+    assert_eq!(report.status, "unchanged");
+    assert!(!report.written);
+    assert_eq!(
+        fs::metadata(fixture.entry()).unwrap().modified().unwrap(),
+        metadata
+    );
+    assert_eq!(fs::read_dir(&fixture.0).unwrap().count(), 1);
+}
+
+#[test]
+fn alias_rename_across_modules_changes_only_live_tokens_and_retains_all_identity() {
+    let fixture = Fixture::new();
+    fixture.put("project.arcadia", "arcadia 7; project rescue \"Rescue\" { include \"participants.arcadia\"; include \"work.arcadia\"; }\n");
+    fixture.put(
+        "participants.arcadia",
+        "// @team is quoted documentation\noa_entity team \"Team @team\" {}\n",
+    );
+    fixture.put("work.arcadia", "oa_activity assess \"Assess\" {}\noa_activity report \"Report\" {}\nallocation assigned \"Assigned\" { source @team; target @assess; }\ninteraction transfer \"Transfer\" { source @assess; target @report; }\n");
+    assert_eq!(fixture.prepare(Operation::Stabilize).write().exit_code, 0);
+    let before = fixture.model();
+    let original: BTreeMap<_, _> = ["project.arcadia", "participants.arcadia", "work.arcadia"]
+        .into_iter()
+        .map(|p| (p, fixture.read(p)))
+        .collect();
+    let team = before
+        .identities()
+        .into_iter()
+        .find(|(_, alias)| *alias == "team")
+        .unwrap()
+        .0;
+    let candidate = fixture.prepare(Operation::RenameAlias {
+        old: "team".into(),
+        new: "rescue_team".into(),
+    });
+    assert_eq!(candidate.report().changes.len(), 2);
+    assert_eq!(fixture.model(), before, "preview cannot mutate");
+    assert_eq!(candidate.write().exit_code, 0);
+    let mut expected = before;
+    expected.elements.get_mut(&team).unwrap().alias = "rescue_team".into();
+    assert_eq!(fixture.model(), expected);
+    assert_eq!(fixture.read("project.arcadia"), original["project.arcadia"]);
+    assert_eq!(
+        fixture.read("participants.arcadia"),
+        original["participants.arcadia"].replacen("oa_entity team ", "oa_entity rescue_team ", 1)
+    );
+    assert_eq!(
+        fixture.read("work.arcadia"),
+        original["work.arcadia"].replace("source @team;", "source @rescue_team;")
+    );
+}
+
+#[test]
+fn invalid_unicode_raw_edit_is_located_and_never_stabilized_or_written() {
+    let fixture = Fixture::new();
+    let raw = "arcadia 7; project p \"雨\" {\n oa_activity a \"A\" {}\n allocation alloc \"Alloc\" { source @missing; target @a; }\n}\n";
+    fixture.put("project.arcadia", raw);
+    for command in [
+        vec!["check"],
+        vec!["stabilize", "--write"],
+        vec!["rename-alias", "a", "b", "--write"],
+    ] {
+        let (code, report) = fixture.cli(&command);
+        assert_eq!(code, 1);
+        assert_eq!(fixture.read("project.arcadia"), raw);
+        let diagnostics = report["diagnostics"].as_array().unwrap();
+        assert!(!diagnostics.is_empty());
+        for d in diagnostics {
+            assert_eq!(d["coordinate_space"], "input");
+            let at = &d["location"];
+            let start = at["start"].as_u64().unwrap() as usize;
+            assert!(raw.is_char_boundary(start));
+            assert_eq!(
+                at["line"].as_u64().unwrap() as usize,
+                raw[..start].bytes().filter(|b| *b == b'\n').count() + 1
+            );
+            let line = raw[..start]
+                .rsplit_once('\n')
+                .map_or(&raw[..start], |(_, tail)| tail);
+            assert_eq!(
+                at["column"].as_u64().unwrap() as usize,
+                line.chars().count() + 1
+            );
+        }
+    }
+}
+
+#[test]
+fn missing_id_warning_uses_raw_location_and_never_exposes_ephemeral_lint_id() {
+    let fixture = Fixture::new();
+    let raw = "arcadia 7;\nproject p \"雨\" {\n    oa_activity work \"Work\" {}\n}\n";
+    fixture.put("project.arcadia", raw);
+    let (code, result) = fixture.cli(&["lint"]);
+    assert_eq!(code, 0, "engineering warnings do not reject admission");
+    let warning = result["diagnostics"]
+        .as_array()
+        .unwrap()
+        .iter()
+        .find(|d| d["code"] == "work_without_behavior_context")
+        .unwrap();
+    assert_eq!(warning["severity"], "warning");
+    assert_eq!(
+        warning["location"]["start"],
+        raw.find("oa_activity").unwrap()
+    );
+    assert_eq!(warning["location"]["line"], 3);
+    assert_eq!(warning["location"]["column"], 5);
+    assert!(warning["object_id"].is_null());
+    assert_eq!(fixture.read("project.arcadia"), raw);
+}
+
+#[test]
+fn captured_dependency_change_refuses_all_writes_even_on_noop() {
+    let fixture = Fixture::new();
+    fixture.put("project.arcadia", SIMPLE);
+    let pending = fixture.prepare(Operation::Stabilize);
+    let external = format!("{SIMPLE}// editor changed this\n");
+    fixture.put("project.arcadia", &external);
+    let result = pending.write();
+    assert_eq!(result.exit_code, 3);
+    assert_eq!(result.diagnostics.last().unwrap().code, "external_change");
+    assert_eq!(fixture.read("project.arcadia"), external);
+    assert_eq!(fixture.prepare(Operation::Stabilize).write().exit_code, 0);
+    let noop = fixture.prepare(Operation::Stabilize);
+    assert!(noop.report().changes.is_empty());
+    let latest = format!("{}// another edit\n", fixture.read("project.arcadia"));
+    fixture.put("project.arcadia", &latest);
+    assert_eq!(noop.write().exit_code, 3);
+    assert_eq!(fixture.read("project.arcadia"), latest);
+}
+
+#[test]
+fn pending_journal_refuses_read_preview_and_write_without_recovery() {
+    let fixture = Fixture::new();
+    fixture.put("project.arcadia", SIMPLE);
+    assert_eq!(fixture.prepare(Operation::Stabilize).write().exit_code, 0);
+    let noop = fixture.prepare(Operation::Stabilize);
+    let source = fixture.read("project.arcadia");
+    // An opaque incomplete journal must never be interpreted/recovered by CLI.
+    let journal = fixture.0.join(".arcadia-save-project.arcadia.journal");
+    fs::create_dir(&journal).unwrap();
+    fs::write(journal.join("sentinel"), b"retain").unwrap();
+    for op in [Operation::Check, Operation::Stabilize] {
+        let report = prepare(&fixture.entry(), op).err().unwrap();
+        assert_eq!(report.exit_code, 3);
+        assert!(report.diagnostics.iter().any(|d| d.code == "pending_save"));
+    }
+    assert_eq!(
+        noop.write().exit_code,
+        3,
+        "saver must recheck after preview"
+    );
+    assert_eq!(fixture.read("project.arcadia"), source);
+    assert_eq!(fs::read(journal.join("sentinel")).unwrap(), b"retain");
+}
+
+#[test]
+fn rejected_alias_and_same_alias_preserve_source() {
+    let fixture = Fixture::new();
+    fixture.put("project.arcadia", SIMPLE);
+    assert_eq!(fixture.prepare(Operation::Stabilize).write().exit_code, 0);
+    let source = fixture.read("project.arcadia");
+    for (old, new) in [
+        ("team", "rescue"),
+        ("team", "invalid alias"),
+        ("absent", "valid"),
+    ] {
+        let (code, result) = fixture.cli(&["rename-alias", old, new, "--write"]);
+        assert_eq!(code, 1);
+        assert_eq!(result["status"], "rejected");
+        assert_eq!(fixture.read("project.arcadia"), source);
+    }
+    let (code, result) = fixture.cli(&["rename-alias", "team", "team", "--write"]);
+    assert_eq!(code, 0);
+    assert_eq!(result["status"], "unchanged");
+    assert_eq!(fixture.read("project.arcadia"), source);
+}
+
+#[test]
+fn rename_shows_missing_identity_and_separate_source_migration() {
+    let fixture = Fixture::new();
+    let old = "// retain\narcadia 5; project p \"P\" { oa_entity team \"Team\" {} }\n";
+    fixture.put("project.arcadia", old);
+    let candidate = fixture.prepare(Operation::RenameAlias {
+        old: "team".into(),
+        new: "crew".into(),
+    });
+    let report = candidate.report();
+    assert_eq!(report.identities_to_stabilize, 2);
+    assert_eq!(report.migration.as_ref().unwrap().from_schema, 5);
+    assert_eq!(report.migration.as_ref().unwrap().to_schema, 7);
+    assert!(report.changes[0].diff.contains("-arcadia 5;"));
+    assert!(report.changes[0].diff.contains("+arcadia 7;"));
+    assert!(report.changes[0].after.contains("oa_entity crew"));
+    assert_eq!(fixture.read("project.arcadia"), old);
+    assert_eq!(candidate.write().exit_code, 0);
+}
+
+#[test]
+fn entry_is_explicit_and_machine_readable_usage_errors_do_not_write() {
+    let fixture = Fixture::new();
+    fixture.put("project.arcadia", SIMPLE);
+    let output = Command::new(env!("CARGO_BIN_EXE_arcadia"))
+        .current_dir(&fixture.0)
+        .args(["check", "--json"])
+        .output()
+        .unwrap();
+    assert_eq!(output.status.code(), Some(2));
+    let error: Value = serde_json::from_slice(&output.stdout).unwrap();
+    assert_eq!(error["diagnostics"][0]["code"], "usage");
+    assert_eq!(fixture.read("project.arcadia"), SIMPLE);
+    let (code, _) = fixture.cli(&["check", "--write"]);
+    assert_eq!(code, 2);
+    assert!(Path::new(env!("CARGO_BIN_EXE_arcadia")).is_file());
+}
+
+#[test]
+fn loader_encoding_missing_dependency_and_invalid_old_source_keep_original_bytes() {
+    let fixture = Fixture::new();
+    let entry = "arcadia 7; project p \"P\" { include \"part.arcadia\"; }";
+    fixture.put("project.arcadia", entry);
+    let (code, report) = fixture.cli(&["stabilize", "--write"]);
+    assert_eq!(code, 3, "a disk dependency could not be read");
+    assert!(
+        report["diagnostics"]
+            .as_array()
+            .unwrap()
+            .iter()
+            .any(|d| d["code"] == "missing_include")
+    );
+    fs::write(fixture.0.join("part.arcadia"), [0xff, 0xfe]).unwrap();
+    let (code, report) = fixture.cli(&["stabilize", "--write"]);
+    assert_eq!(code, 1, "invalid encoding is invalid raw source");
+    assert!(
+        report["diagnostics"]
+            .as_array()
+            .unwrap()
+            .iter()
+            .any(|d| d["code"] == "source_encoding")
+    );
+    assert_eq!(fixture.read("project.arcadia"), entry);
+    assert_eq!(
+        fs::read(fixture.0.join("part.arcadia")).unwrap(),
+        [0xff, 0xfe]
+    );
+    for raw in [
+        "arcadia 5; project p \"P\" { oa_entity a \"A\" { ??? } }",
+        "arcadia 2; project p \"P\" {}",
+    ] {
+        fixture.put("project.arcadia", raw);
+        let (code, _) = fixture.cli(&["stabilize", "--write"]);
+        assert_eq!(code, 1);
+        assert_eq!(fixture.read("project.arcadia"), raw);
+    }
+}
+
+#[test]
+fn non_element_alias_detached_file_and_unchanged_dependency_conflict() {
+    let fixture = Fixture::new();
+    fixture.put("project.arcadia", "arcadia 7; project p \"P\" { include \"part.arcadia\"; oa_activity a \"A\" {} allocation responsible \"Responsible\" { source @ // keep edge comment\nteam; target @a; } }");
+    fixture.put("part.arcadia", "oa_entity team \"Team\" {}");
+    fixture.put(
+        "detached.arcadia",
+        "invalid detached draft must stay exact 雨",
+    );
+    assert_eq!(fixture.prepare(Operation::Stabilize).write().exit_code, 0);
+    let before = fixture.model();
+    let relation = before
+        .identities()
+        .into_iter()
+        .find(|(_, alias)| *alias == "responsible")
+        .unwrap()
+        .0;
+    let (code, _) = fixture.cli(&["rename-alias", "responsible", "performs", "--write"]);
+    assert_eq!(code, 0);
+    let mut expected = before;
+    expected.relations.get_mut(&relation).unwrap().alias = "performs".into();
+    assert_eq!(fixture.model(), expected);
+    assert!(
+        fixture
+            .read("project.arcadia")
+            .contains("@ // keep edge comment\nteam")
+    );
+    let captured = fixture.prepare(Operation::RenameAlias {
+        old: "p".into(),
+        new: "rescue".into(),
+    });
+    assert!(
+        captured
+            .report()
+            .changes
+            .iter()
+            .all(|c| c.path != "part.arcadia")
+    );
+    let root_before = fixture.read("project.arcadia");
+    fixture.put("part.arcadia", "// external unchanged-dependency edit\n");
+    assert_eq!(captured.write().exit_code, 3);
+    assert_eq!(fixture.read("project.arcadia"), root_before);
+    assert_eq!(
+        fixture.read("part.arcadia"),
+        "// external unchanged-dependency edit\n"
+    );
+    assert_eq!(
+        fixture.read("detached.arcadia"),
+        "invalid detached draft must stay exact 雨"
+    );
+}

crates/oa-core/Cargo.toml

@@ -12,6 +12,9 @@ uuid.workspace = true
 thiserror.workspace = true
 tempfile = "3"
 same-file = "1"
+num-bigint = "0.5.1"
+num-integer = "0.1.47"
+num-traits = "0.2.19"
 
 [target.'cfg(target_os = "linux")'.dependencies]
 libc = "0.2"

crates/oa-core/examples/attachment_snapshot.rs

@@ -0,0 +1,27 @@
+//! Read and validate a saved acceptance fixture without rewriting its source.
+//! cargo run --locked -p oa-core --example attachment_snapshot -- input.arcadia output.json
+use oa_core::{persistence, validate_candidate};
+use std::{fs::OpenOptions, io::Write, path::Path};
+
+fn main() -> Result<(), Box<dyn std::error::Error>> {
+    let args: Vec<_> = std::env::args_os().skip(1).collect();
+    if args.len() != 2 {
+        return Err("Expected input source/JSON and a new output JSON path".into());
+    }
+    let project = persistence::load(Path::new(&args[0]))?;
+    validate_candidate(&project)?;
+    let bytes = serde_json::to_vec_pretty(&project)?;
+    let mut output = OpenOptions::new()
+        .write(true)
+        .create_new(true)
+        .open(&args[1])?;
+    output.write_all(&bytes)?;
+    output.write_all(b"\n")?;
+    output.sync_all()?;
+    println!(
+        "Validated {} objects and {} views; saved a complete Project snapshot",
+        project.identities().len(),
+        project.diagrams.len()
+    );
+    Ok(())
+}

crates/oa-core/examples/release_dense_views.rs

@@ -230,7 +230,7 @@ fn fixture() -> (Project, Id, Vec<Id>, Vec<Id>, Vec<Id>) {
             )
         })
         .collect();
-    p.diagrams.insert(diagram, Diagram { id: diagram, alias: "forty_exchange_view".into(), name: "Forty service exchanges · all concerns".into(), description: "Start with All. Compare first category, overlapping concerns, global coverage and chosen processes. No hand-routed edges.".into(), layer: Layer::Oa, projection: ProjectionKind::FunctionalDataflow, view_options: ViewOptions::default(), nodes, routes: vec![] });
+    p.diagrams.insert(diagram, Diagram { id: diagram, alias: "forty_exchange_view".into(), name: "Forty service exchanges · all concerns".into(), description: "Start with All. Compare first category, overlapping concerns, global coverage and chosen processes. No hand-routed edges.".into(), layer: Layer::Oa, projection: ProjectionKind::FunctionalDataflow, view_options: ViewOptions::default(), nodes, layout: None, routes: vec![] });
     (p, diagram, exchanges, categories, contexts)
 }
 

crates/oa-core/examples/state_bend_routing_snapshot.rs

@@ -0,0 +1,101 @@
+//! Read-only saved-State geometry evidence for a predeclared native bend trial.
+//!
+//! Usage:
+//! state_bend_routing_snapshot INPUT.arcadia NEW_OUTPUT.json
+//!
+//! Loads and validates the complete Project, then independently projects/routes
+//! every saved State view through core APIs. The complete Project permits exact
+//! semantic and presentation comparison; derived geometry permits declaring a
+//! segment and insertion position before native actions. No desktop command,
+//! planner, gesture, or pin insertion helper is called. Input is never written;
+//! output uses create_new and fails rather than overwriting an existing file.
+//!
+//! Limits: this shares production core routing, so it is not an independent
+//! mathematical test of that router, nor evidence of UI picking/gesture success.
+//! It does not generate expected mutations or adapt an oracle to observed edits.
+//! The acceptance recipe must declare the intended segment/index/point and exact
+//! Project mutation before UI execution, and bind this executable/source/input
+//! and output hashes externally. Warning strings are diagnostic Debug output,
+//! not a stable interchange schema. Missing/hidden/internal transitions have no
+//! routed edge; their semantic records remain in the complete Project snapshot.
+
+use oa_core::{persistence, projection, routing, validate_candidate};
+use serde_json::json;
+use std::{fs::OpenOptions, io::Write, path::Path};
+
+fn main() -> Result<(), Box<dyn std::error::Error>> {
+    let args: Vec<_> = std::env::args_os().skip(1).collect();
+    if args.len() != 2 {
+        return Err("Expected input source/JSON and a new output JSON path".into());
+    }
+    let project = persistence::load(Path::new(&args[0]))?;
+    validate_candidate(&project)?;
+    let mut views = Vec::new();
+    for (diagram_id, diagram) in &project.diagrams {
+        let Some(machine) = diagram.projection.state_machine() else {
+            continue;
+        };
+        let projected = projection::project_diagram(&project, diagram);
+        let routed = routing::route_diagram(&project, diagram, &projected);
+        let edges: Vec<_> = routed
+            .edges
+            .iter()
+            .map(|(edge_id, edge)| {
+                json!({
+                    "edge": edge_id,
+                    "id": edge.id,
+                    "points": edge.points,
+                    "pins": edge.pins,
+                    "pin_fractions": edge.pin_fractions,
+                    "custom_suspended": edge.custom_suspended,
+                    "warnings": edge.warnings.iter().map(|warning| format!("{warning:?}")).collect::<Vec<_>>(),
+                    "label": {
+                        "text": edge.label.text,
+                        "fraction": edge.label.fraction,
+                        "anchor": edge.label.anchor,
+                        "center": edge.label.center,
+                        "bounds": {
+                            "position": edge.label.bounds.position,
+                            "size": edge.label.bounds.size
+                        }
+                    }
+                })
+            })
+            .collect();
+        views.push(json!({
+            "diagram": diagram_id,
+            "machine": machine,
+            "projected": projected,
+            "routed_bounds": {
+                "position": routed.bounds.position,
+                "size": routed.bounds.size
+            },
+            "routed_edges": edges
+        }));
+    }
+    // Preserve the canonical typed Project serialization (including f32
+    // formatting). Serializing it through Value directly promotes f32 to f64.
+    let project_json: serde_json::Value = serde_json::from_slice(&serde_json::to_vec(&project)?)?;
+    let snapshot = json!({
+        "schema": "state-bend-routing-snapshot/v1",
+        "project": project_json,
+        "state_views": views
+    });
+    // Finish all reading, validation, routing and serialization before creating
+    // the new evidence file. A failed load cannot leave an apparent snapshot.
+    let mut bytes = serde_json::to_vec_pretty(&snapshot)?;
+    bytes.push(b'\n');
+    let mut output = OpenOptions::new()
+        .write(true)
+        .create_new(true)
+        .open(&args[1])?;
+    output.write_all(&bytes)?;
+    output.sync_all()?;
+    println!(
+        "Validated {} objects and {} saved views; snapshotted {} State views and the complete Project",
+        project.identities().len(),
+        project.diagrams.len(),
+        views.len()
+    );
+    Ok(())
+}

crates/oa-core/src/analysis_numeric.rs

@@ -0,0 +1,103 @@
+//! Exact numeric foundation for analysis; no model, expression, or package resolver.
+//!
+//! Values use reduced rational coordinates. All nontrivial arithmetic takes one
+//! request-local [WorkMeter]. The future evaluator must also charge *expanded*
+//! expression/call/property/list/target visits and retain the same logical walk on
+//! cache hits. Stored AST size is not a dynamic execution limit.
+//!
+//! Approximate engineering functions/irrational unit scales require a subsequent
+//! explicit numeric profile; rationals do not implement degree/radian conversion
+//! or transcendental mathematics.
+
+mod dimension;
+mod exact;
+mod meter;
+mod quantity;
+
+pub use dimension::{Dimension, DimensionAxis};
+pub use exact::{Exact, ExactWire};
+pub use meter::{
+    EvaluationStep, NumericOperation, WorkExhaustion, WorkLimits, WorkMeter, WorkResource,
+    WorkSite, WorkUsage,
+};
+pub use quantity::{NumericType, NumericValue, ResolvedKind, Unit};
+
+use serde::{Deserialize, Serialize};
+use thiserror::Error;
+
+/// Profile identity includes the accounting rules, not crate-internal timing.
+pub const WORK_PROFILE: &str = "Q1-logical-work-1";
+pub const MAX_COMPONENT_BITS: u64 = 4096;
+/// Cross products require 8192 bits; their sum can require one additional bit.
+pub const MAX_INTERMEDIATE_BITS: u64 = 8193;
+pub const MAX_COMPONENT_DIGITS: usize = 1234;
+pub const MAX_DECIMAL_EXPONENT: i32 = 128;
+pub const MAX_INTEGER_POWER: i8 = 16;
+/// Includes ratio punctuation/whitespace without permitting unbounded scanning.
+pub const MAX_LITERAL_BYTES: usize = 2 * MAX_COMPONENT_DIGITS + 32;
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Serialize, Deserialize)]
+pub enum NumberComponent {
+    Numerator,
+    Denominator,
+}
+
+#[derive(Debug, Clone, PartialEq, Eq, Error, Serialize, Deserialize)]
+pub enum NumericLimit {
+    #[error("request work exhausted: {0}")]
+    Work(WorkExhaustion),
+    #[error("{component:?} uses {bits} bits, above the {limit}-bit {stage} limit")]
+    Bits {
+        component: NumberComponent,
+        bits: u64,
+        limit: u64,
+        stage: String,
+    },
+}
+
+#[derive(Debug, Clone, PartialEq, Eq, Error, Serialize, Deserialize)]
+pub enum NumericError {
+    #[error("numeric limit: {0}")]
+    Limit(NumericLimit),
+    #[error("invalid numeric literal")]
+    InvalidLiteral,
+    #[error("numeric literal exceeds its digit or byte limit")]
+    LiteralTooLong,
+    #[error("decimal exponent is outside -128 through 128")]
+    DecimalExponent,
+    #[error("wire rational is not in canonical reduced form")]
+    NonCanonicalWire,
+    #[error("rational denominator is zero")]
+    ZeroDenominator,
+    #[error("division by zero")]
+    DivisionByZero,
+    #[error("zero to the power zero is undefined in this profile")]
+    ZeroPowerZero,
+    #[error("integer power is outside -16 through 16")]
+    IntegerPower,
+    #[error("dimension exponent at {axis:?} is outside -32 through 32: {value}")]
+    DimensionExponent { axis: DimensionAxis, value: i32 },
+    #[error("unit scale must be strictly positive")]
+    UnitScale,
+    #[error("a linear unit must have zero offset")]
+    LinearOffset,
+    #[error("an affine point must have a distinct linear difference kind")]
+    DifferenceKind,
+    #[error("numeric kinds or dimensions are incompatible")]
+    IncompatibleTypes,
+    #[error("operation is not defined for affine points")]
+    AffineOperation,
+    #[error("AsKind requires an anonymous matching dimension and a linear target")]
+    KindAssertion,
+    #[error("request work limits exceed the provisional reference ceilings")]
+    InvalidWorkLimits,
+}
+
+impl NumericError {
+    pub fn is_terminal_work_exhaustion(&self) -> bool {
+        matches!(self, Self::Limit(NumericLimit::Work(_)))
+    }
+}
+
+#[cfg(test)]
+mod tests;

crates/oa-core/src/analysis_numeric/dimension.rs

@@ -0,0 +1,107 @@
+use super::NumericError;
+use serde::{Deserialize, Serialize};
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Serialize, Deserialize)]
+pub enum DimensionAxis {
+    Length,
+    Mass,
+    Time,
+    ElectricCurrent,
+    Temperature,
+    Amount,
+    LuminousIntensity,
+}
+
+impl DimensionAxis {
+    pub const ALL: [Self; 7] = [
+        Self::Length,
+        Self::Mass,
+        Self::Time,
+        Self::ElectricCurrent,
+        Self::Temperature,
+        Self::Amount,
+        Self::LuminousIntensity,
+    ];
+}
+
+/// SI base-dimension vector in DimensionAxis::ALL order, each entry -32..=32.
+/// This is a dimension, never a nominal quantity-kind compatibility proof.
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash, Serialize, Deserialize)]
+#[serde(try_from = "[i16; 7]", into = "[i16; 7]")]
+pub struct Dimension([i16; 7]);
+
+impl Dimension {
+    pub const ZERO: Self = Self([0; 7]);
+
+    pub fn new(exponents: [i16; 7]) -> Result<Self, NumericError> {
+        for (index, value) in exponents.iter().copied().enumerate() {
+            if !(-32..=32).contains(&value) {
+                return Err(NumericError::DimensionExponent {
+                    axis: DimensionAxis::ALL[index],
+                    value: i32::from(value),
+                });
+            }
+        }
+        Ok(Self(exponents))
+    }
+
+    pub fn exponents(self) -> [i16; 7] {
+        self.0
+    }
+
+    pub fn is_dimensionless(self) -> bool {
+        self == Self::ZERO
+    }
+
+    pub fn checked_product(self, rhs: Self) -> Result<Self, NumericError> {
+        self.combine(rhs, 1)
+    }
+
+    pub fn checked_quotient(self, rhs: Self) -> Result<Self, NumericError> {
+        self.combine(rhs, -1)
+    }
+
+    pub fn checked_power(self, exponent: i8) -> Result<Self, NumericError> {
+        if !(-super::MAX_INTEGER_POWER..=super::MAX_INTEGER_POWER).contains(&exponent) {
+            return Err(NumericError::IntegerPower);
+        }
+        let mut output = [0; 7];
+        for (index, value) in self.0.iter().enumerate() {
+            output[index] = Self::checked_exponent(index, i32::from(*value) * i32::from(exponent))?;
+        }
+        Ok(Self(output))
+    }
+
+    fn combine(self, rhs: Self, sign: i32) -> Result<Self, NumericError> {
+        let mut output = [0; 7];
+        for (index, value) in self.0.iter().enumerate() {
+            output[index] =
+                Self::checked_exponent(index, i32::from(*value) + sign * i32::from(rhs.0[index]))?;
+        }
+        Ok(Self(output))
+    }
+
+    fn checked_exponent(index: usize, value: i32) -> Result<i16, NumericError> {
+        if !(-32..=32).contains(&value) {
+            return Err(NumericError::DimensionExponent {
+                axis: DimensionAxis::ALL[index],
+                value,
+            });
+        }
+        Ok(value as i16)
+    }
+}
+
+impl TryFrom<[i16; 7]> for Dimension {
+    type Error = NumericError;
+
+    fn try_from(value: [i16; 7]) -> Result<Self, Self::Error> {
+        Self::new(value)
+    }
+}
+
+impl From<Dimension> for [i16; 7] {
+    fn from(value: Dimension) -> Self {
+        value.0
+    }
+}

crates/oa-core/src/analysis_numeric/exact.rs

@@ -0,0 +1,469 @@
+use super::meter::{normalization_cost, parse_cost, product_cost, sum_cost, words};
+use super::{
+    MAX_COMPONENT_BITS, MAX_COMPONENT_DIGITS, MAX_DECIMAL_EXPONENT, MAX_INTEGER_POWER,
+    MAX_INTERMEDIATE_BITS, MAX_LITERAL_BYTES, NumberComponent, NumericError, NumericLimit,
+    NumericOperation, WorkLimits, WorkMeter,
+};
+use num_bigint::BigInt;
+use num_integer::Integer;
+use num_traits::{One, Signed, Zero};
+use serde::{Deserialize, Serialize};
+use std::cmp::Ordering;
+
+/// The interchange representation deliberately does not use num-bigint's serde
+/// format or JSON numeric values. Duplicate/missing/unknown fields reject.
+/// Its derived decoder allocates String fields before numeric validation; a
+/// transport/document adapter must bound the encoded envelope and decoded text.
+#[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
+#[serde(deny_unknown_fields)]
+pub struct ExactWire {
+    pub numerator: String,
+    pub denominator: String,
+}
+
+/// Reduced rational with positive denominator and <=4096-bit components.
+///
+/// There are no unmetered arithmetic/ordering traits. Eq is structural equality
+/// of already normalized bounded values, not an expression comparison API.
+/// Standalone serde admission bounds the subsequent BigInt validation, not the
+/// preceding String decoding. Document adapters must bound encoded/decoded input
+/// and aggregate admission work. Evaluation uses one explicit WorkMeter.
+#[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
+#[serde(try_from = "ExactWire", into = "ExactWire")]
+pub struct Exact {
+    numerator: BigInt,
+    denominator: BigInt,
+}
+
+impl Exact {
+    pub fn from_integer(value: i64) -> Self {
+        Self {
+            numerator: BigInt::from(value),
+            denominator: BigInt::one(),
+        }
+    }
+
+    pub fn is_zero(&self) -> bool {
+        self.numerator.is_zero()
+    }
+
+    pub fn is_positive(&self) -> bool {
+        self.numerator.is_positive()
+    }
+
+    pub fn component_bits(&self) -> (u64, u64) {
+        (self.numerator.bits(), self.denominator.bits())
+    }
+
+    pub fn to_wire(&self) -> ExactWire {
+        ExactWire {
+            numerator: self.numerator.to_string(),
+            denominator: self.denominator.to_string(),
+        }
+    }
+
+    /// Canonical *literal* spelling, not a generic expression formatter.
+    /// Negative literal nodes use ratio(-n,d), even when d=1. A leading minus
+    /// belongs to the future expression parser's UnaryNegate node instead.
+    pub fn canonical_literal(&self) -> String {
+        if self.denominator.is_one() && !self.numerator.is_negative() {
+            self.numerator.to_string()
+        } else {
+            format!("ratio({}, {})", self.numerator, self.denominator)
+        }
+    }
+
+    pub fn from_wire(wire: &ExactWire, meter: &mut WorkMeter) -> Result<Self, NumericError> {
+        meter.ensure_active()?;
+        let n_digits = wire_digits(&wire.numerator, true)?;
+        let d_digits = wire_digits(&wire.denominator, false)?;
+        let n_bound = decimal_bits(n_digits.len());
+        let d_bound = decimal_bits(d_digits.len());
+        meter.numeric(
+            NumericOperation::ParseWire,
+            parse_cost(n_digits.len(), n_bound)
+                + parse_cost(d_digits.len(), d_bound)
+                + normalization_cost(n_bound, d_bound),
+        )?;
+        let numerator = parse_integer(&wire.numerator)?;
+        let denominator = parse_integer(&wire.denominator)?;
+        Self::check_bits(&numerator, &denominator, MAX_COMPONENT_BITS, "wire")?;
+        if denominator.is_zero() {
+            return Err(NumericError::ZeroDenominator);
+        }
+        if !numerator.gcd(&denominator).is_one() {
+            return Err(NumericError::NonCanonicalWire);
+        }
+        Ok(Self {
+            numerator,
+            denominator,
+        })
+    }
+
+    /// Reads one unsigned decimal/integer atom or a ratio(n,d) literal only.
+    /// It does not parse expressions, unary operators, units, calls or names.
+    /// Source ratios/decimals may reduce; wire values must already be canonical.
+    pub fn parse_literal(source: &str, meter: &mut WorkMeter) -> Result<Self, NumericError> {
+        meter.ensure_active()?;
+        if source.len() > MAX_LITERAL_BYTES {
+            return Err(NumericError::LiteralTooLong);
+        }
+        let source = trim_ascii(source);
+        if let Some(body) = source.strip_prefix("ratio(") {
+            let body = body.strip_suffix(')').ok_or(NumericError::InvalidLiteral)?;
+            let (n, d) = body.split_once(',').ok_or(NumericError::InvalidLiteral)?;
+            return Self::parse_ratio(trim_ascii(n), trim_ascii(d), meter);
+        }
+        Self::parse_decimal(source, meter)
+    }
+
+    fn parse_ratio(n: &str, d: &str, meter: &mut WorkMeter) -> Result<Self, NumericError> {
+        let n_digits = source_integer_digits(n, true)?;
+        let d_digits = source_integer_digits(d, false)?;
+        let n_bound = decimal_bits(n_digits.len());
+        let d_bound = decimal_bits(d_digits.len());
+        Self::check_estimates(n_bound, d_bound)?;
+        meter.numeric(
+            NumericOperation::ParseLiteral,
+            parse_cost(n_digits.len(), n_bound)
+                + parse_cost(d_digits.len(), d_bound)
+                + normalization_cost(n_bound, d_bound),
+        )?;
+        Self::normalize_precharged(parse_integer(n)?, parse_integer(d)?)
+    }
+
+    fn parse_decimal(source: &str, meter: &mut WorkMeter) -> Result<Self, NumericError> {
+        let mut parts = source.split(['e', 'E']);
+        let mantissa = parts.next().ok_or(NumericError::InvalidLiteral)?;
+        let exponent = match parts.next() {
+            Some(text) => parse_exponent(text)?,
+            None => 0,
+        };
+        if parts.next().is_some() {
+            return Err(NumericError::InvalidLiteral);
+        }
+        let (whole, fraction) = match mantissa.split_once('.') {
+            Some((whole, fraction)) if !fraction.is_empty() => (whole, fraction),
+            Some(_) => return Err(NumericError::InvalidLiteral),
+            None => (mantissa, ""),
+        };
+        source_integer_digits(whole, false)?;
+        if !fraction.bytes().all(|byte| byte.is_ascii_digit()) {
+            return Err(NumericError::InvalidLiteral);
+        }
+        let digit_count = whole.len() + fraction.len();
+        if digit_count > MAX_COMPONENT_DIGITS {
+            return Err(NumericError::LiteralTooLong);
+        }
+        let adjustment = exponent - fraction.len() as i32;
+        let power = adjustment.unsigned_abs();
+        let mantissa_bound = decimal_bits(digit_count);
+        let scale_bound = decimal_bits(power as usize + 1);
+        let (n_bound, d_bound) = if adjustment >= 0 {
+            (mantissa_bound + scale_bound, 1)
+        } else {
+            (mantissa_bound, scale_bound)
+        };
+        Self::check_estimates(n_bound, d_bound)?;
+        // Fixed logical allowance for constructing 10^power; independent of
+        // num-bigint's selected multiplication/exponentiation implementation.
+        let power_steps = 1 + 2 * u64::from(u32::BITS - power.leading_zeros());
+        meter.numeric(
+            NumericOperation::ParseLiteral,
+            parse_cost(digit_count, mantissa_bound)
+                + power_steps * product_cost(scale_bound, scale_bound)
+                + product_cost(mantissa_bound, scale_bound)
+                + normalization_cost(n_bound, d_bound),
+        )?;
+        let digits = format!("{whole}{fraction}");
+        let mut numerator = parse_integer(&digits)?;
+        let scale = BigInt::from(10_u8).pow(power);
+        let denominator = if adjustment >= 0 {
+            numerator *= scale;
+            BigInt::one()
+        } else {
+            scale
+        };
+        Self::normalize_precharged(numerator, denominator)
+    }
+
+    pub fn add(&self, rhs: &Self, meter: &mut WorkMeter) -> Result<Self, NumericError> {
+        self.add_or_subtract(rhs, false, meter)
+    }
+
+    pub fn subtract(&self, rhs: &Self, meter: &mut WorkMeter) -> Result<Self, NumericError> {
+        self.add_or_subtract(rhs, true, meter)
+    }
+
+    fn add_or_subtract(
+        &self,
+        rhs: &Self,
+        subtract: bool,
+        meter: &mut WorkMeter,
+    ) -> Result<Self, NumericError> {
+        let (a, b) = self.component_bits();
+        let (c, d) = rhs.component_bits();
+        let left_bound = a + d;
+        let right_bound = c + b;
+        let n_bound = left_bound.max(right_bound) + 1;
+        let d_bound = b + d;
+        Self::check_estimates(n_bound, d_bound)?;
+        meter.numeric(
+            if subtract {
+                NumericOperation::Subtract
+            } else {
+                NumericOperation::Add
+            },
+            product_cost(a, d)
+                + product_cost(c, b)
+                + sum_cost(left_bound, right_bound)
+                + product_cost(b, d)
+                + normalization_cost(n_bound, d_bound),
+        )?;
+        let left = &self.numerator * &rhs.denominator;
+        let right = &rhs.numerator * &self.denominator;
+        let numerator = if subtract { left - right } else { left + right };
+        let denominator = &self.denominator * &rhs.denominator;
+        Self::normalize_precharged(numerator, denominator)
+    }
+
+    pub fn multiply(&self, rhs: &Self, meter: &mut WorkMeter) -> Result<Self, NumericError> {
+        let (a, b) = self.component_bits();
+        let (c, d) = rhs.component_bits();
+        Self::check_estimates(a + c, b + d)?;
+        meter.numeric(
+            NumericOperation::Multiply,
+            product_cost(a, c) + product_cost(b, d) + normalization_cost(a + c, b + d),
+        )?;
+        Self::normalize_precharged(
+            &self.numerator * &rhs.numerator,
+            &self.denominator * &rhs.denominator,
+        )
+    }
+
+    pub fn divide(&self, rhs: &Self, meter: &mut WorkMeter) -> Result<Self, NumericError> {
+        let (a, b) = self.component_bits();
+        let (c, d) = rhs.component_bits();
+        Self::check_estimates(a + d, b + c)?;
+        meter.numeric(
+            NumericOperation::Divide,
+            product_cost(a, d) + product_cost(b, c) + normalization_cost(a + d, b + c),
+        )?;
+        if rhs.is_zero() {
+            return Err(NumericError::DivisionByZero);
+        }
+        Self::normalize_precharged(
+            &self.numerator * &rhs.denominator,
+            &self.denominator * &rhs.numerator,
+        )
+    }
+
+    pub fn compare(&self, rhs: &Self, meter: &mut WorkMeter) -> Result<Ordering, NumericError> {
+        let (a, b) = self.component_bits();
+        let (c, d) = rhs.component_bits();
+        Self::check_estimates((a + d).max(c + b), 1)?;
+        meter.numeric(
+            NumericOperation::Compare,
+            product_cost(a, d) + product_cost(c, b) + sum_cost(a + d, c + b),
+        )?;
+        Ok((&self.numerator * &rhs.denominator).cmp(&(&rhs.numerator * &self.denominator)))
+    }
+
+    pub fn negated(&self, meter: &mut WorkMeter) -> Result<Self, NumericError> {
+        meter.numeric(NumericOperation::Negate, self.copy_cost())?;
+        Ok(Self {
+            numerator: -&self.numerator,
+            denominator: self.denominator.clone(),
+        })
+    }
+
+    pub fn absolute(&self, meter: &mut WorkMeter) -> Result<Self, NumericError> {
+        meter.numeric(NumericOperation::Absolute, self.copy_cost())?;
+        Ok(Self {
+            numerator: self.numerator.abs(),
+            denominator: self.denominator.clone(),
+        })
+    }
+
+    pub fn reciprocal(&self, meter: &mut WorkMeter) -> Result<Self, NumericError> {
+        meter.numeric(NumericOperation::Reciprocal, self.copy_cost())?;
+        if self.is_zero() {
+            return Err(NumericError::DivisionByZero);
+        }
+        Ok(Self {
+            numerator: if self.numerator.is_negative() {
+                -&self.denominator
+            } else {
+                self.denominator.clone()
+            },
+            denominator: self.numerator.abs(),
+        })
+    }
+
+    /// Fixed left-to-right repeated multiplication, at most 16 multiplications.
+    /// Each reduced stage obeys the same component bound; no large power is
+    /// allocated and subsequently discarded after discovering it is oversized.
+    pub fn power(&self, exponent: i8, meter: &mut WorkMeter) -> Result<Self, NumericError> {
+        meter.numeric(NumericOperation::Power, self.copy_cost())?;
+        if !(-MAX_INTEGER_POWER..=MAX_INTEGER_POWER).contains(&exponent) {
+            return Err(NumericError::IntegerPower);
+        }
+        if self.is_zero() && exponent == 0 {
+            return Err(NumericError::ZeroPowerZero);
+        }
+        let factor = if exponent < 0 {
+            self.reciprocal(meter)?
+        } else {
+            self.clone()
+        };
+        let mut value = Self::from_integer(1);
+        for _ in 0..exponent.unsigned_abs() {
+            value = value.multiply(&factor, meter)?;
+        }
+        Ok(value)
+    }
+
+    pub(super) fn copy_cost(&self) -> u64 {
+        let (n, d) = self.component_bits();
+        1 + words(n) + words(d)
+    }
+
+    fn normalize_precharged(
+        mut numerator: BigInt,
+        mut denominator: BigInt,
+    ) -> Result<Self, NumericError> {
+        Self::check_bits(
+            &numerator,
+            &denominator,
+            MAX_INTERMEDIATE_BITS,
+            "intermediate",
+        )?;
+        if denominator.is_zero() {
+            return Err(NumericError::ZeroDenominator);
+        }
+        if denominator.is_negative() {
+            numerator = -numerator;
+            denominator = -denominator;
+        }
+        let gcd = numerator.gcd(&denominator);
+        numerator /= &gcd;
+        denominator /= gcd;
+        Self::check_bits(&numerator, &denominator, MAX_COMPONENT_BITS, "reduced")?;
+        Ok(Self {
+            numerator,
+            denominator,
+        })
+    }
+
+    fn check_estimates(n: u64, d: u64) -> Result<(), NumericError> {
+        Self::check_bit_count(
+            n,
+            NumberComponent::Numerator,
+            MAX_INTERMEDIATE_BITS,
+            "predicted",
+        )?;
+        Self::check_bit_count(
+            d,
+            NumberComponent::Denominator,
+            MAX_INTERMEDIATE_BITS,
+            "predicted",
+        )
+    }
+
+    fn check_bits(n: &BigInt, d: &BigInt, limit: u64, stage: &str) -> Result<(), NumericError> {
+        Self::check_bit_count(n.bits(), NumberComponent::Numerator, limit, stage)?;
+        Self::check_bit_count(d.bits(), NumberComponent::Denominator, limit, stage)
+    }
+
+    fn check_bit_count(
+        bits: u64,
+        component: NumberComponent,
+        limit: u64,
+        stage: &str,
+    ) -> Result<(), NumericError> {
+        if bits > limit {
+            return Err(NumericError::Limit(NumericLimit::Bits {
+                component,
+                bits,
+                limit,
+                stage: stage.to_owned(),
+            }));
+        }
+        Ok(())
+    }
+}
+
+impl TryFrom<ExactWire> for Exact {
+    type Error = NumericError;
+
+    fn try_from(value: ExactWire) -> Result<Self, Self::Error> {
+        // BigInt validation is bounded after ExactWire strings have decoded.
+        // The adapter owns envelope/text/aggregate admission bounds and must not
+        // reset evaluation meters.
+        Self::from_wire(&value, &mut WorkMeter::new(WorkLimits::REFERENCE))
+    }
+}
+
+impl From<Exact> for ExactWire {
+    fn from(value: Exact) -> Self {
+        value.to_wire()
+    }
+}
+
+fn trim_ascii(text: &str) -> &str {
+    text.trim_matches(|ch: char| ch.is_ascii_whitespace())
+}
+
+fn source_integer_digits(text: &str, signed: bool) -> Result<&str, NumericError> {
+    let digits = if signed {
+        text.strip_prefix('-').unwrap_or(text)
+    } else {
+        text
+    };
+    if digits.len() > MAX_COMPONENT_DIGITS {
+        return Err(NumericError::LiteralTooLong);
+    }
+    if digits.is_empty() || !digits.bytes().all(|byte| byte.is_ascii_digit()) {
+        return Err(NumericError::InvalidLiteral);
+    }
+    Ok(digits)
+}
+
+fn wire_digits(text: &str, signed: bool) -> Result<&str, NumericError> {
+    let digits = source_integer_digits(text, signed).map_err(|error| match error {
+        NumericError::LiteralTooLong => error,
+        _ => NumericError::NonCanonicalWire,
+    })?;
+    if (digits.len() > 1 && digits.starts_with('0')) || (text.starts_with('-') && digits == "0") {
+        return Err(NumericError::NonCanonicalWire);
+    }
+    Ok(digits)
+}
+
+fn parse_integer(text: &str) -> Result<BigInt, NumericError> {
+    BigInt::parse_bytes(text.as_bytes(), 10).ok_or(NumericError::InvalidLiteral)
+}
+
+fn parse_exponent(text: &str) -> Result<i32, NumericError> {
+    let (negative, digits) = if let Some(digits) = text.strip_prefix('-') {
+        (true, digits)
+    } else {
+        (false, text.strip_prefix('+').unwrap_or(text))
+    };
+    if digits.is_empty() || !digits.bytes().all(|byte| byte.is_ascii_digit()) {
+        return Err(NumericError::InvalidLiteral);
+    }
+    let mut value = 0_i32;
+    for digit in digits.bytes() {
+        value = value * 10 + i32::from(digit - b'0');
+        if value > MAX_DECIMAL_EXPONENT {
+            return Err(NumericError::DecimalExponent);
+        }
+    }
+    Ok(if negative { -value } else { value })
+}
+
+fn decimal_bits(digits: usize) -> u64 {
+    // 3.322 exceeds log2(10); dimensions are bounded before this conversion.
+    (digits as u64 * 3322).div_ceil(1000).max(1)
+}

crates/oa-core/src/analysis_numeric/fixtures/r7-literal-boundaries.json

@@ -0,0 +1,32 @@
+[
+  {
+    "canonical_source": "1000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000",
+    "expression": {
+      "Number": {
+        "denominator": "1",
+        "numerator": "1000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+      }
+    },
+    "name": "ten_to_300"
+  },
+  {
+    "canonical_source": "ratio(1, 522194440706576253345876355358312191289982124523691890192116741641976953985778728424413405967498779170445053357219631418993786719092896803631618043925682638972978488271854999170180795067191859157214035005927973113188159419698856372836167342172293308748403954352901852035642024370059304557233988891799014503343469488440893892973452815095130470299789726716411734651513348221529512507986199933857107770846917779942645743159118957217248367043905936319748237550094520674504208530837546834166925275516486044134775384991808184705966507606898412918594045916828375610659246423184062775112999150206172392431297837246097308511903252956622805412865917690043804311051417135098849101156584508839003337597742539960818209685142687562392007453579567729991395256699805775897135553415567045292136442139895777424891477161767258532611634530697452993846501061481697843891439474220308003706472837459911525285821188577408160690315522951458068463354171428220365223949985950890732881736611925133626529949897998045399734600887312408859224933727829625089164535236559716582775403784110923285873186648442456409760158728501220463308455437074192539205964902261490928669488824051563042951500651206733594863336608245755565801460390869016718045121902354170201577095168)",
+    "expression": {
+      "Number": {
+        "denominator": "522194440706576253345876355358312191289982124523691890192116741641976953985778728424413405967498779170445053357219631418993786719092896803631618043925682638972978488271854999170180795067191859157214035005927973113188159419698856372836167342172293308748403954352901852035642024370059304557233988891799014503343469488440893892973452815095130470299789726716411734651513348221529512507986199933857107770846917779942645743159118957217248367043905936319748237550094520674504208530837546834166925275516486044134775384991808184705966507606898412918594045916828375610659246423184062775112999150206172392431297837246097308511903252956622805412865917690043804311051417135098849101156584508839003337597742539960818209685142687562392007453579567729991395256699805775897135553415567045292136442139895777424891477161767258532611634530697452993846501061481697843891439474220308003706472837459911525285821188577408160690315522951458068463354171428220365223949985950890732881736611925133626529949897998045399734600887312408859224933727829625089164535236559716582775403784110923285873186648442456409760158728501220463308455437074192539205964902261490928669488824051563042951500651206733594863336608245755565801460390869016718045121902354170201577095168",
+        "numerator": "1"
+      }
+    },
+    "name": "one_over_two_to_4095"
+  },
+  {
+    "canonical_source": "ratio(-1044388881413152506691752710716624382579964249047383780384233483283953907971557456848826811934997558340890106714439262837987573438185793607263236087851365277945956976543709998340361590134383718314428070011855946226376318839397712745672334684344586617496807908705803704071284048740118609114467977783598029006686938976881787785946905630190260940599579453432823469303026696443059025015972399867714215541693835559885291486318237914434496734087811872639496475100189041349008417061675093668333850551032972088269550769983616369411933015213796825837188091833656751221318492846368125550225998300412344784862595674492194617023806505913245610825731835380087608622102834270197698202313169017678006675195485079921636419370285375124784014907159135459982790513399611551794271106831134090584272884279791554849782954323534517065223269061394905987693002122963395687782878948440616007412945674919823050571642377154816321380631045902916136926708342856440730447899971901781465763473223850267253059899795996090799469201774624817718449867455659250178329070473119433165550807568221846571746373296884912819520317457002440926616910874148385078411929804522981857338977648103126085903001302413467189726673216491511131602920781738033436090243804708340403154190335, 1)",
+    "expression": {
+      "Number": {
+        "denominator": "1",
+        "numerator": "-1044388881413152506691752710716624382579964249047383780384233483283953907971557456848826811934997558340890106714439262837987573438185793607263236087851365277945956976543709998340361590134383718314428070011855946226376318839397712745672334684344586617496807908705803704071284048740118609114467977783598029006686938976881787785946905630190260940599579453432823469303026696443059025015972399867714215541693835559885291486318237914434496734087811872639496475100189041349008417061675093668333850551032972088269550769983616369411933015213796825837188091833656751221318492846368125550225998300412344784862595674492194617023806505913245610825731835380087608622102834270197698202313169017678006675195485079921636419370285375124784014907159135459982790513399611551794271106831134090584272884279791554849782954323534517065223269061394905987693002122963395687782878948440616007412945674919823050571642377154816321380631045902916136926708342856440730447899971901781465763473223850267253059899795996090799469201774624817718449867455659250178329070473119433165550807568221846571746373296884912819520317457002440926616910874148385078411929804522981857338977648103126085903001302413467189726673216491511131602920781738033436090243804708340403154190335"
+      }
+    },
+    "name": "negative_4096_bit_bound"
+  }
+]

crates/oa-core/src/analysis_numeric/meter.rs

@@ -0,0 +1,240 @@
+use super::{NumericError, NumericLimit};
+use serde::{Deserialize, Serialize};
+use thiserror::Error;
+
+/// Every event is charged once per dynamic occurrence, before entering it.
+///
+/// A Call expression therefore charges Expression and CalculationEntry; a
+/// Property read charges Expression and PropertyBinding. List element visits
+/// are additional to evaluation of their expressions. Only executed branches
+/// are charged. Targets are sorted by category (properties, then checks), then
+/// stable UUID bytes, by the integrating evaluator.
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Serialize, Deserialize)]
+pub enum EvaluationStep {
+    Target,
+    Expression,
+    CalculationEntry,
+    PropertyBinding,
+    ListElement,
+}
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Serialize, Deserialize)]
+pub enum NumericOperation {
+    ParseWire,
+    ParseLiteral,
+    Add,
+    Subtract,
+    Multiply,
+    Divide,
+    Compare,
+    Negate,
+    Absolute,
+    Reciprocal,
+    Power,
+    KindAssertion,
+}
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Serialize, Deserialize)]
+pub enum WorkResource {
+    DynamicEvents,
+    NumericUnits,
+}
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Serialize, Deserialize)]
+pub enum WorkSite {
+    Evaluation(EvaluationStep),
+    Numeric(NumericOperation),
+}
+
+/// Failed reservations consume no partial charge. The first failure is latched.
+#[derive(Debug, Clone, PartialEq, Eq, Error, Serialize, Deserialize)]
+#[error("{resource:?}: used {used}, requested {requested}, limit {limit}, at {site:?}")]
+pub struct WorkExhaustion {
+    pub resource: WorkResource,
+    pub used: u64,
+    pub requested: u64,
+    pub limit: u64,
+    pub site: WorkSite,
+}
+
+/// Provisional calibration ceilings, not measured execution-time guarantees.
+///
+/// Effective limits, profile identity, capture, targets and context must all be
+/// recorded in request/result/frozen identity. A caller may lower these ceilings.
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Serialize, Deserialize)]
+#[serde(try_from = "WorkLimitsWire", into = "WorkLimitsWire")]
+pub struct WorkLimits {
+    dynamic_events: u64,
+    numeric_units: u64,
+}
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Serialize, Deserialize)]
+#[serde(deny_unknown_fields)]
+struct WorkLimitsWire {
+    dynamic_events: u64,
+    numeric_units: u64,
+}
+
+impl WorkLimits {
+    pub const REFERENCE: Self = Self {
+        dynamic_events: 1_000_000,
+        numeric_units: 50_000_000,
+    };
+
+    pub fn new(dynamic_events: u64, numeric_units: u64) -> Result<Self, NumericError> {
+        if dynamic_events > Self::REFERENCE.dynamic_events
+            || numeric_units > Self::REFERENCE.numeric_units
+        {
+            return Err(NumericError::InvalidWorkLimits);
+        }
+        Ok(Self {
+            dynamic_events,
+            numeric_units,
+        })
+    }
+
+    pub fn dynamic_events(self) -> u64 {
+        self.dynamic_events
+    }
+
+    pub fn numeric_units(self) -> u64 {
+        self.numeric_units
+    }
+}
+
+impl TryFrom<WorkLimitsWire> for WorkLimits {
+    type Error = NumericError;
+
+    fn try_from(value: WorkLimitsWire) -> Result<Self, Self::Error> {
+        Self::new(value.dynamic_events, value.numeric_units)
+    }
+}
+
+impl From<WorkLimits> for WorkLimitsWire {
+    fn from(value: WorkLimits) -> Self {
+        Self {
+            dynamic_events: value.dynamic_events,
+            numeric_units: value.numeric_units,
+        }
+    }
+}
+
+#[derive(Debug, Clone, Copy, Default, PartialEq, Eq, Serialize, Deserialize)]
+#[serde(deny_unknown_fields)]
+pub struct WorkUsage {
+    pub dynamic_events: u64,
+    pub numeric_units: u64,
+}
+
+/// Intentionally neither Clone nor Default: pass the same mutable meter through
+/// every target, numeric operation and expanded call in one evaluation request.
+///
+/// Exhaustion is terminal. Integrators must stop traversing siblings/targets and
+/// mark already collected causes as incomplete. Replaying an aggregate cache
+/// cost is insufficient if it changes the exact exhaustion location; initially
+/// retain logical traversal even when numerical values come from a cache.
+#[derive(Debug)]
+pub struct WorkMeter {
+    limits: WorkLimits,
+    usage: WorkUsage,
+    exhausted: Option<WorkExhaustion>,
+}
+
+impl WorkMeter {
+    pub fn new(limits: WorkLimits) -> Self {
+        Self {
+            limits,
+            usage: WorkUsage::default(),
+            exhausted: None,
+        }
+    }
+
+    pub fn limits(&self) -> WorkLimits {
+        self.limits
+    }
+
+    pub fn usage(&self) -> WorkUsage {
+        self.usage
+    }
+
+    pub fn exhaustion(&self) -> Option<&WorkExhaustion> {
+        self.exhausted.as_ref()
+    }
+
+    pub fn ensure_active(&self) -> Result<(), NumericError> {
+        match &self.exhausted {
+            Some(failure) => Err(NumericError::Limit(NumericLimit::Work(failure.clone()))),
+            None => Ok(()),
+        }
+    }
+
+    pub fn visit(&mut self, step: EvaluationStep) -> Result<(), NumericError> {
+        self.reserve(WorkResource::DynamicEvents, 1, WorkSite::Evaluation(step))
+    }
+
+    pub(super) fn numeric(
+        &mut self,
+        operation: NumericOperation,
+        units: u64,
+    ) -> Result<(), NumericError> {
+        self.reserve(
+            WorkResource::NumericUnits,
+            units,
+            WorkSite::Numeric(operation),
+        )
+    }
+
+    fn reserve(
+        &mut self,
+        resource: WorkResource,
+        requested: u64,
+        site: WorkSite,
+    ) -> Result<(), NumericError> {
+        self.ensure_active()?;
+        let (used, limit) = match resource {
+            WorkResource::DynamicEvents => (self.usage.dynamic_events, self.limits.dynamic_events),
+            WorkResource::NumericUnits => (self.usage.numeric_units, self.limits.numeric_units),
+        };
+        // Subtraction is safe: only successful reservations update usage.
+        if requested > limit - used {
+            let failure = WorkExhaustion {
+                resource,
+                used,
+                requested,
+                limit,
+                site,
+            };
+            self.exhausted = Some(failure.clone());
+            return Err(NumericError::Limit(NumericLimit::Work(failure)));
+        }
+        match resource {
+            WorkResource::DynamicEvents => self.usage.dynamic_events += requested,
+            WorkResource::NumericUnits => self.usage.numeric_units += requested,
+        }
+        Ok(())
+    }
+}
+
+// Logical 64-bit words are platform independent. These are deterministic
+// accounting weights, not a claim about num-bigint's internal algorithm/timing.
+pub(super) fn words(bits: u64) -> u64 {
+    bits.max(1).div_ceil(64)
+}
+
+pub(super) fn product_cost(a_bits: u64, b_bits: u64) -> u64 {
+    1 + words(a_bits) * words(b_bits)
+}
+
+pub(super) fn sum_cost(a_bits: u64, b_bits: u64) -> u64 {
+    1 + words(a_bits.max(b_bits))
+}
+
+pub(super) fn normalization_cost(n_bits: u64, d_bits: u64) -> u64 {
+    let width = words(n_bits.max(d_bits));
+    // 64*w² for GCD plus 2*w² for the two quotient operations.
+    1 + 66 * width * width
+}
+
+pub(super) fn parse_cost(digits: usize, estimated_bits: u64) -> u64 {
+    1 + digits as u64 * words(estimated_bits)
+}

crates/oa-core/src/analysis_numeric/quantity.rs

@@ -0,0 +1,378 @@
+use super::{Dimension, Exact, MAX_INTEGER_POWER, NumericError, NumericOperation, WorkMeter};
+use std::cmp::Ordering;
+
+/// K is supplied by the common resolver's verified nominal compatibility
+/// relation. It is not inferred from dimension/name/symbol/archive bytes here.
+/// Coordinate basis/algebra/difference-kind closure must be part of that proof.
+/// Exact definition references and pins remain the caller's provenance.
+/// K must be a bounded, cheap-to-clone/compare verified handle. Constructing or
+/// comparing an unbounded rooted contract graph is resolver admission work and
+/// must not be hidden inside K's Clone/Eq implementations. Rust trait bounds do
+/// not enforce this resource contract.
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub struct ResolvedKind<K> {
+    key: K,
+    dimension: Dimension,
+    difference: Option<K>,
+}
+
+impl<K> ResolvedKind<K> {
+    pub fn linear(key: K, dimension: Dimension) -> Self {
+        Self {
+            key,
+            dimension,
+            difference: None,
+        }
+    }
+
+    pub fn key(&self) -> &K {
+        &self.key
+    }
+
+    pub fn dimension(&self) -> Dimension {
+        self.dimension
+    }
+
+    pub fn is_affine(&self) -> bool {
+        self.difference.is_some()
+    }
+}
+
+impl<K: Clone + Eq> ResolvedKind<K> {
+    pub fn affine(key: K, difference: &Self) -> Result<Self, NumericError> {
+        if difference.is_affine() || key == difference.key {
+            return Err(NumericError::DifferenceKind);
+        }
+        Ok(Self {
+            key,
+            dimension: difference.dimension,
+            difference: Some(difference.key.clone()),
+        })
+    }
+
+    pub fn difference_kind(&self) -> Option<Self> {
+        self.difference
+            .as_ref()
+            .map(|key| Self::linear(key.clone(), self.dimension))
+    }
+}
+
+/// Canonical coordinate = magnitude * scale + offset.
+/// Unit symbols and display preferences are outside this numeric representation.
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub struct Unit<K> {
+    kind: ResolvedKind<K>,
+    scale: Exact,
+    offset: Exact,
+}
+
+impl<K: Clone + Eq> Unit<K> {
+    pub fn new(kind: ResolvedKind<K>, scale: Exact, offset: Exact) -> Result<Self, NumericError> {
+        if !scale.is_positive() {
+            return Err(NumericError::UnitScale);
+        }
+        if !kind.is_affine() && !offset.is_zero() {
+            return Err(NumericError::LinearOffset);
+        }
+        Ok(Self {
+            kind,
+            scale,
+            offset,
+        })
+    }
+
+    pub fn kind(&self) -> &ResolvedKind<K> {
+        &self.kind
+    }
+
+    pub fn scale(&self) -> &Exact {
+        &self.scale
+    }
+
+    pub fn offset(&self) -> &Exact {
+        &self.offset
+    }
+
+    /// Fixed multiply-then-add path. Each reduced arithmetic stage is bounded.
+    /// A mathematically cancelling wider intermediate still reports NumericLimit;
+    /// replacing this path with a fused operation requires a new work profile.
+    pub fn to_canonical(
+        &self,
+        magnitude: &Exact,
+        meter: &mut WorkMeter,
+    ) -> Result<Exact, NumericError> {
+        magnitude
+            .multiply(&self.scale, meter)?
+            .add(&self.offset, meter)
+    }
+
+    /// Fixed subtract-then-divide path; never rounds a coordinate.
+    pub fn from_canonical(
+        &self,
+        coordinate: &Exact,
+        meter: &mut WorkMeter,
+    ) -> Result<Exact, NumericError> {
+        coordinate
+            .subtract(&self.offset, meter)?
+            .divide(&self.scale, meter)
+    }
+
+    pub fn convert(
+        &self,
+        magnitude: &Exact,
+        target: &Self,
+        meter: &mut WorkMeter,
+    ) -> Result<Exact, NumericError> {
+        meter.ensure_active()?;
+        if self.kind != target.kind {
+            return Err(NumericError::IncompatibleTypes);
+        }
+        target.from_canonical(&self.to_canonical(magnitude, meter)?, meter)
+    }
+}
+
+/// Internal numerical types. Boolean/list/check semantics belong to the common
+/// expression evaluator. Anonymous zero dimension normalizes to Number.
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub enum NumericType<K> {
+    Number,
+    Named(ResolvedKind<K>),
+    Anonymous(Dimension),
+}
+
+impl<K> NumericType<K> {
+    pub fn dimension(&self) -> Dimension {
+        match self {
+            Self::Number => Dimension::ZERO,
+            Self::Named(kind) => kind.dimension,
+            Self::Anonymous(dimension) => *dimension,
+        }
+    }
+
+    pub fn is_affine(&self) -> bool {
+        matches!(self, Self::Named(kind) if kind.is_affine())
+    }
+
+    fn anonymous(dimension: Dimension) -> Self {
+        if dimension.is_dimensionless() {
+            Self::Number
+        } else {
+            Self::Anonymous(dimension)
+        }
+    }
+
+    fn normalized(self) -> Self {
+        match self {
+            Self::Anonymous(dimension) => Self::anonymous(dimension),
+            other => other,
+        }
+    }
+}
+
+/// A canonical rational coordinate with an internal numerical type.
+///
+/// Derived Eq compares stored representation. Formal equality/ordering must call
+/// compare(), which rejects mismatched nominal kinds instead of treating them
+/// as a false predicate. Public property output must still check its declared
+/// type and anchor the result to that declaration's exact definition reference.
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub struct NumericValue<K> {
+    value_type: NumericType<K>,
+    coordinate: Exact,
+}
+
+impl<K: Clone + Eq> NumericValue<K> {
+    pub fn new(value_type: NumericType<K>, coordinate: Exact) -> Self {
+        Self {
+            value_type: value_type.normalized(),
+            coordinate,
+        }
+    }
+
+    pub fn number(coordinate: Exact) -> Self {
+        Self::new(NumericType::Number, coordinate)
+    }
+
+    pub fn from_unit(
+        magnitude: &Exact,
+        unit: &Unit<K>,
+        meter: &mut WorkMeter,
+    ) -> Result<Self, NumericError> {
+        meter.ensure_active()?;
+        Ok(Self::new(
+            NumericType::Named(unit.kind.clone()),
+            unit.to_canonical(magnitude, meter)?,
+        ))
+    }
+
+    pub fn value_type(&self) -> &NumericType<K> {
+        &self.value_type
+    }
+
+    pub fn coordinate(&self) -> &Exact {
+        &self.coordinate
+    }
+
+    pub fn display_in(&self, unit: &Unit<K>, meter: &mut WorkMeter) -> Result<Exact, NumericError> {
+        meter.ensure_active()?;
+        if !matches!(&self.value_type, NumericType::Named(kind) if kind == &unit.kind) {
+            return Err(NumericError::IncompatibleTypes);
+        }
+        unit.from_canonical(&self.coordinate, meter)
+    }
+
+    pub fn add(&self, rhs: &Self, meter: &mut WorkMeter) -> Result<Self, NumericError> {
+        meter.ensure_active()?;
+        let output = self.additive_type(rhs, false)?;
+        Ok(Self::new(
+            output,
+            self.coordinate.add(&rhs.coordinate, meter)?,
+        ))
+    }
+
+    pub fn subtract(&self, rhs: &Self, meter: &mut WorkMeter) -> Result<Self, NumericError> {
+        meter.ensure_active()?;
+        let output = self.additive_type(rhs, true)?;
+        Ok(Self::new(
+            output,
+            self.coordinate.subtract(&rhs.coordinate, meter)?,
+        ))
+    }
+
+    fn additive_type(&self, rhs: &Self, subtract: bool) -> Result<NumericType<K>, NumericError> {
+        use NumericType::{Anonymous, Named, Number};
+        match (&self.value_type, &rhs.value_type) {
+            (Number, Number) => Ok(Number),
+            (Anonymous(left), Anonymous(right)) if left == right => Ok(Anonymous(*left)),
+            (Named(left), Named(right)) => match (&left.difference, &right.difference) {
+                (None, None) if left == right => Ok(Named(left.clone())),
+                (Some(difference), Some(_)) if subtract && left == right => Ok(Named(
+                    ResolvedKind::linear(difference.clone(), left.dimension),
+                )),
+                (Some(difference), None)
+                    if difference == &right.key && left.dimension == right.dimension =>
+                {
+                    Ok(Named(left.clone()))
+                }
+                (None, Some(difference))
+                    if !subtract
+                        && difference == &left.key
+                        && left.dimension == right.dimension =>
+                {
+                    Ok(Named(right.clone()))
+                }
+                _ => Err(NumericError::IncompatibleTypes),
+            },
+            _ => Err(NumericError::IncompatibleTypes),
+        }
+    }
+
+    pub fn multiply(&self, rhs: &Self, meter: &mut WorkMeter) -> Result<Self, NumericError> {
+        meter.ensure_active()?;
+        let output = self.multiplicative_type(rhs, false)?;
+        Ok(Self::new(
+            output,
+            self.coordinate.multiply(&rhs.coordinate, meter)?,
+        ))
+    }
+
+    pub fn divide(&self, rhs: &Self, meter: &mut WorkMeter) -> Result<Self, NumericError> {
+        meter.ensure_active()?;
+        let output = self.multiplicative_type(rhs, true)?;
+        Ok(Self::new(
+            output,
+            self.coordinate.divide(&rhs.coordinate, meter)?,
+        ))
+    }
+
+    fn multiplicative_type(
+        &self,
+        rhs: &Self,
+        divide: bool,
+    ) -> Result<NumericType<K>, NumericError> {
+        use NumericType::Number;
+        if self.value_type.is_affine() || rhs.value_type.is_affine() {
+            return Err(NumericError::AffineOperation);
+        }
+        match (&self.value_type, &rhs.value_type) {
+            (Number, Number) => Ok(Number),
+            (_, Number) => Ok(self.value_type.clone()),
+            (Number, _) if !divide => Ok(rhs.value_type.clone()),
+            _ => {
+                let left = self.value_type.dimension();
+                let right = rhs.value_type.dimension();
+                let dimension = if divide {
+                    left.checked_quotient(right)?
+                } else {
+                    left.checked_product(right)?
+                };
+                Ok(NumericType::anonymous(dimension))
+            }
+        }
+    }
+
+    pub fn negated(&self, meter: &mut WorkMeter) -> Result<Self, NumericError> {
+        meter.ensure_active()?;
+        if self.value_type.is_affine() {
+            return Err(NumericError::AffineOperation);
+        }
+        Ok(Self::new(
+            self.value_type.clone(),
+            self.coordinate.negated(meter)?,
+        ))
+    }
+
+    pub fn absolute(&self, meter: &mut WorkMeter) -> Result<Self, NumericError> {
+        meter.ensure_active()?;
+        if self.value_type.is_affine() {
+            return Err(NumericError::AffineOperation);
+        }
+        Ok(Self::new(
+            self.value_type.clone(),
+            self.coordinate.absolute(meter)?,
+        ))
+    }
+
+    pub fn power(&self, exponent: i8, meter: &mut WorkMeter) -> Result<Self, NumericError> {
+        meter.ensure_active()?;
+        if !(-MAX_INTEGER_POWER..=MAX_INTEGER_POWER).contains(&exponent) {
+            return Err(NumericError::IntegerPower);
+        }
+        if self.value_type.is_affine() {
+            return Err(NumericError::AffineOperation);
+        }
+        let output = match exponent {
+            0 => NumericType::Number,
+            1 => self.value_type.clone(),
+            _ => NumericType::anonymous(self.value_type.dimension().checked_power(exponent)?),
+        };
+        Ok(Self::new(output, self.coordinate.power(exponent, meter)?))
+    }
+
+    pub fn compare(&self, rhs: &Self, meter: &mut WorkMeter) -> Result<Ordering, NumericError> {
+        meter.ensure_active()?;
+        if self.value_type != rhs.value_type {
+            return Err(NumericError::IncompatibleTypes);
+        }
+        self.coordinate.compare(&rhs.coordinate, meter)
+    }
+
+    pub fn as_kind(
+        &self,
+        target: &ResolvedKind<K>,
+        meter: &mut WorkMeter,
+    ) -> Result<Self, NumericError> {
+        meter.ensure_active()?;
+        if target.is_affine()
+            || matches!(self.value_type, NumericType::Named(_))
+            || self.value_type.dimension() != target.dimension
+        {
+            return Err(NumericError::KindAssertion);
+        }
+        meter.numeric(NumericOperation::KindAssertion, self.coordinate.copy_cost())?;
+        Ok(Self::new(
+            NumericType::Named(target.clone()),
+            self.coordinate.clone(),
+        ))
+    }
+}

crates/oa-core/src/analysis_numeric/tests.rs

@@ -0,0 +1,804 @@
+use super::*;
+use num_bigint::BigInt;
+use num_traits::One;
+use std::cmp::Ordering;
+
+fn meter() -> WorkMeter {
+    WorkMeter::new(WorkLimits::REFERENCE)
+}
+
+fn exact(n: impl ToString, d: impl ToString) -> Exact {
+    Exact::from_wire(
+        &ExactWire {
+            numerator: n.to_string(),
+            denominator: d.to_string(),
+        },
+        &mut meter(),
+    )
+    .unwrap()
+}
+
+fn source(text: &str) -> Exact {
+    Exact::parse_literal(text, &mut meter()).unwrap()
+}
+
+fn assert_fraction(value: &Exact, n: impl ToString, d: impl ToString) {
+    assert_eq!(
+        value.to_wire(),
+        ExactWire {
+            numerator: n.to_string(),
+            denominator: d.to_string(),
+        }
+    );
+}
+
+// Independent bounded i128 oracle. It does not call the production Exact/GCD
+// implementation when deriving expected arithmetic or ordering.
+fn small_fraction(mut n: i128, mut d: i128) -> (i128, i128) {
+    assert_ne!(d, 0);
+    if d < 0 {
+        n = -n;
+        d = -d;
+    }
+    let (mut a, mut b) = (n.abs(), d);
+    while b != 0 {
+        (a, b) = (b, a % b);
+    }
+    (n / a, d / a)
+}
+
+#[test]
+fn arithmetic_matches_independent_small_integer_oracle() {
+    for a in [-5_i128, -2, 0, 1, 4] {
+        for b in [1_i128, 2, 3, 7] {
+            for c in [-5_i128, -2, 0, 1, 4] {
+                for d in [1_i128, 2, 3, 7] {
+                    let (an, ad) = small_fraction(a, b);
+                    let (bn, bd) = small_fraction(c, d);
+                    let left = exact(an, ad);
+                    let right = exact(bn, bd);
+                    let mut work = meter();
+                    let (n, den) = small_fraction(a * d + c * b, b * d);
+                    assert_fraction(&left.add(&right, &mut work).unwrap(), n, den);
+                    let (n, den) = small_fraction(a * d - c * b, b * d);
+                    assert_fraction(&left.subtract(&right, &mut work).unwrap(), n, den);
+                    let (n, den) = small_fraction(a * c, b * d);
+                    assert_fraction(&left.multiply(&right, &mut work).unwrap(), n, den);
+                    if c != 0 {
+                        let (n, den) = small_fraction(a * d, b * c);
+                        assert_fraction(&left.divide(&right, &mut work).unwrap(), n, den);
+                    } else {
+                        assert_eq!(
+                            left.divide(&right, &mut work),
+                            Err(NumericError::DivisionByZero)
+                        );
+                    }
+                    assert_eq!(
+                        left.compare(&right, &mut work).unwrap(),
+                        (a * d).cmp(&(c * b))
+                    );
+                }
+            }
+        }
+    }
+}
+
+#[test]
+fn decimals_are_exact_and_source_ratios_reduce() {
+    assert_fraction(
+        &source("0.1").add(&source("0.2"), &mut meter()).unwrap(),
+        3,
+        10,
+    );
+    assert_fraction(&source("0.50"), 1, 2);
+    assert_fraction(&source("12.50e-2"), 1, 8);
+    assert_fraction(&source("1e+3"), 1000, 1);
+    assert_fraction(&source("0001.2500"), 5, 4);
+    assert_fraction(&source(" ratio( -6, 8 ) "), -3, 4);
+    assert_fraction(&source("ratio(-0, 27)"), 0, 1);
+    assert_eq!(source("0.5").canonical_literal(), "ratio(1, 2)");
+    assert_eq!(source("42").canonical_literal(), "42");
+}
+
+#[test]
+fn powers_and_signs_have_explicit_domains() {
+    let x = exact(-2, 3);
+    assert_fraction(&x.power(3, &mut meter()).unwrap(), -8, 27);
+    assert_fraction(&x.power(-3, &mut meter()).unwrap(), -27, 8);
+    assert_fraction(&x.power(0, &mut meter()).unwrap(), 1, 1);
+    assert_fraction(&x.absolute(&mut meter()).unwrap(), 2, 3);
+    assert_fraction(&x.negated(&mut meter()).unwrap(), 2, 3);
+    assert_fraction(&x.reciprocal(&mut meter()).unwrap(), -3, 2);
+    let zero = Exact::from_integer(0);
+    assert_eq!(
+        zero.power(0, &mut meter()),
+        Err(NumericError::ZeroPowerZero)
+    );
+    assert_eq!(
+        zero.power(-1, &mut meter()),
+        Err(NumericError::DivisionByZero)
+    );
+    assert_eq!(x.power(17, &mut meter()), Err(NumericError::IntegerPower));
+    assert_eq!(
+        x.power(i8::MIN, &mut meter()),
+        Err(NumericError::IntegerPower)
+    );
+}
+
+#[test]
+fn canonical_wire_rejects_both_component_noncanonical_forms() {
+    for (n, d) in [
+        ("+1", "1"),
+        ("01", "1"),
+        ("-0", "1"),
+        ("1", "+1"),
+        ("1", "-1"),
+        ("1", "01"),
+        ("2", "4"),
+        ("0", "3"),
+        ("", "1"),
+        ("1", ""),
+        ("1.0", "1"),
+        ("1", "1.0"),
+        ("1e1", "1"),
+        ("1", "1e1"),
+        (" 1", "1"),
+        ("1", "1 "),
+    ] {
+        assert!(
+            Exact::from_wire(
+                &ExactWire {
+                    numerator: n.into(),
+                    denominator: d.into()
+                },
+                &mut meter(),
+            )
+            .is_err(),
+            "accepted {n}/{d}"
+        );
+    }
+    assert_eq!(
+        Exact::from_wire(
+            &ExactWire {
+                numerator: "1".into(),
+                denominator: "0".into()
+            },
+            &mut meter()
+        ),
+        Err(NumericError::ZeroDenominator)
+    );
+    assert_fraction(&exact(0, 1), 0, 1);
+    assert_fraction(&exact(-1, 2), -1, 2);
+}
+
+#[test]
+fn serde_uses_closed_canonical_string_wire() {
+    let value = exact(-3, 7);
+    let encoded = serde_json::to_value(&value).unwrap();
+    assert_eq!(
+        encoded,
+        serde_json::json!({"numerator":"-3","denominator":"7"})
+    );
+    assert_eq!(serde_json::from_value::<Exact>(encoded).unwrap(), value);
+    for invalid in [
+        r#"{"numerator":1,"denominator":"2"}"#,
+        r#"{"numerator":"1","denominator":2}"#,
+        r#"{"numerator":"1","denominator":"2","other":0}"#,
+        r#"{"numerator":"1","numerator":"2","denominator":"3"}"#,
+        r#"{"numerator":"1"}"#,
+        r#"{"numerator":"2","denominator":"4"}"#,
+    ] {
+        assert!(serde_json::from_str::<Exact>(invalid).is_err(), "{invalid}");
+    }
+}
+
+#[test]
+fn literal_reader_does_not_fold_expression_unary_minus() {
+    assert_eq!(
+        Exact::parse_literal("-2", &mut meter()),
+        Err(NumericError::InvalidLiteral)
+    );
+    let negative_literal = source("ratio(-2, 1)");
+    assert_eq!(negative_literal.canonical_literal(), "ratio(-2, 1)");
+    assert_eq!(source("2").negated(&mut meter()).unwrap(), negative_literal);
+    // Equality of coordinates does not claim AST equality. The expression
+    // parser must preserve UnaryNegate independently of its operand literal.
+    assert_eq!(source("2").canonical_literal(), "2");
+}
+
+#[test]
+fn literal_syntax_and_decimal_exponent_are_bounded() {
+    for invalid in [
+        "",
+        "-",
+        "+1",
+        ".5",
+        "1.",
+        "1.2.3",
+        "1e",
+        "1ee2",
+        "1e+-2",
+        "1_000",
+        "NaN",
+        "Infinity",
+        "1/2",
+        "ratio(1)",
+        "ratio(1,2,3)",
+        "ratio(1,-2)",
+        "ratio(+1,2)",
+        "ratio(1,2) + 1",
+        "１２",
+    ] {
+        assert!(
+            Exact::parse_literal(invalid, &mut meter()).is_err(),
+            "{invalid}"
+        );
+    }
+    for invalid in ["1e129", "1e-129", "1e9999999999999999999999"] {
+        assert_eq!(
+            Exact::parse_literal(invalid, &mut meter()),
+            Err(NumericError::DecimalExponent)
+        );
+    }
+    assert!(Exact::parse_literal("1e128", &mut meter()).is_ok());
+    assert!(Exact::parse_literal("1e-128", &mut meter()).is_ok());
+    assert_eq!(
+        Exact::parse_literal(&"1".repeat(MAX_COMPONENT_DIGITS + 1), &mut meter()),
+        Err(NumericError::LiteralTooLong)
+    );
+    assert_eq!(
+        Exact::parse_literal(&" ".repeat(MAX_LITERAL_BYTES + 1), &mut meter()),
+        Err(NumericError::LiteralTooLong)
+    );
+}
+
+#[test]
+fn full_independent_r7_packets_round_trip_as_literals_and_wire() {
+    let packets: serde_json::Value =
+        serde_json::from_str(include_str!("fixtures/r7-literal-boundaries.json")).unwrap();
+    for packet in packets.as_array().unwrap() {
+        let wire: ExactWire =
+            serde_json::from_value(packet["expression"]["Number"].clone()).unwrap();
+        let expected = Exact::from_wire(&wire, &mut meter()).unwrap();
+        let spelling = packet["canonical_source"].as_str().unwrap();
+        assert_eq!(expected.canonical_literal(), spelling);
+        assert_eq!(
+            Exact::parse_literal(spelling, &mut meter()).unwrap(),
+            expected
+        );
+        let serialized = serde_json::to_string(&expected).unwrap();
+        assert_eq!(
+            serde_json::from_str::<Exact>(&serialized).unwrap(),
+            expected
+        );
+        assert_eq!(expected.to_wire(), wire);
+    }
+}
+
+#[test]
+fn full_8193_bit_sum_intermediate_can_reduce_to_admitted_value() {
+    // N=(2^4096)-1, D=N-1. gcd(N,D)=1 and D is even.
+    // N/D + N/D = N/(D/2), although its un-reduced numerator needs 8193 bits.
+    let n = (BigInt::one() << 4096_usize) - 1_u8;
+    let d = &n - 1_u8;
+    let value = exact(&n, &d);
+    let result = value.add(&value, &mut meter()).unwrap();
+    assert_fraction(&result, &n, &d / 2_u8);
+}
+
+#[test]
+fn cross_products_cancel_before_reduced_component_limit() {
+    let n = BigInt::one() << 4095_usize;
+    let d = &n - 1_u8;
+    let left = exact(&n, &d);
+    let right = exact(&d, &n);
+    assert_fraction(&left.multiply(&right, &mut meter()).unwrap(), 1, 1);
+    assert_fraction(
+        &left
+            .add(&left.negated(&mut meter()).unwrap(), &mut meter())
+            .unwrap(),
+        0,
+        1,
+    );
+}
+
+#[test]
+fn both_reduced_component_overflows_are_reported() {
+    let n = BigInt::one() << 4095_usize;
+    let mut work = meter();
+    let failure = exact(&n, 1)
+        .multiply(&Exact::from_integer(2), &mut work)
+        .unwrap_err();
+    assert!(matches!(
+        failure,
+        NumericError::Limit(NumericLimit::Bits {
+            component: NumberComponent::Numerator,
+            bits: 4097,
+            ..
+        })
+    ));
+    assert!(work.exhaustion().is_none());
+    let failure = exact(1, &n)
+        .divide(&Exact::from_integer(2), &mut work)
+        .unwrap_err();
+    assert!(matches!(
+        failure,
+        NumericError::Limit(NumericLimit::Bits {
+            component: NumberComponent::Denominator,
+            bits: 4097,
+            ..
+        })
+    ));
+    // Value overflow is a nonterminal supported-operation failure; fuel
+    // exhaustion, in contrast, terminates the entire request.
+    assert_fraction(&source("1").add(&source("1"), &mut work).unwrap(), 2, 1);
+}
+
+#[test]
+fn wire_rejects_4097_bits_before_gcd_can_reduce_them() {
+    let oversized = (BigInt::one() << 4096_usize).to_string();
+    for wire in [
+        ExactWire {
+            numerator: oversized.clone(),
+            denominator: "1".into(),
+        },
+        ExactWire {
+            numerator: "1".into(),
+            denominator: oversized.clone(),
+        },
+        ExactWire {
+            numerator: oversized.clone(),
+            denominator: oversized,
+        },
+    ] {
+        assert!(matches!(
+            Exact::from_wire(&wire, &mut meter()),
+            Err(NumericError::Limit(NumericLimit::Bits { stage, .. })) if stage == "wire"
+        ));
+    }
+}
+
+#[test]
+fn numeric_precharge_precedes_big_integer_result_allocation() {
+    let n = BigInt::one() << 4095_usize;
+    let left = exact(&n, 1);
+    let mut work = WorkMeter::new(WorkLimits::new(10, 0).unwrap());
+    let failure = left
+        .multiply(&Exact::from_integer(2), &mut work)
+        .unwrap_err();
+    assert!(failure.is_terminal_work_exhaustion());
+    assert_eq!(work.usage().numeric_units, 0);
+    assert!(matches!(
+        work.exhaustion().unwrap().site,
+        WorkSite::Numeric(NumericOperation::Multiply)
+    ));
+    // With available fuel the same operation reaches the 4097-bit result check.
+    assert!(matches!(
+        left.multiply(&Exact::from_integer(2), &mut meter()),
+        Err(NumericError::Limit(NumericLimit::Bits { .. }))
+    ));
+    let too_wide_wire = ExactWire {
+        numerator: (BigInt::one() << 4096_usize).to_string(),
+        denominator: "1".into(),
+    };
+    let mut parse_work = WorkMeter::new(WorkLimits::new(0, 0).unwrap());
+    assert!(
+        Exact::from_wire(&too_wide_wire, &mut parse_work)
+            .unwrap_err()
+            .is_terminal_work_exhaustion()
+    );
+}
+
+#[test]
+fn provisional_limits_and_effective_limits_round_trip() {
+    let limits = WorkLimits::new(500, 2000).unwrap();
+    let encoded = serde_json::to_value(limits).unwrap();
+    assert_eq!(
+        encoded,
+        serde_json::json!({"dynamic_events":500,"numeric_units":2000})
+    );
+    assert_eq!(
+        serde_json::from_value::<WorkLimits>(encoded).unwrap(),
+        limits
+    );
+    assert_eq!(
+        WorkLimits::new(1_000_001, 0),
+        Err(NumericError::InvalidWorkLimits)
+    );
+    assert_eq!(
+        WorkLimits::new(0, 50_000_001),
+        Err(NumericError::InvalidWorkLimits)
+    );
+    assert!(
+        serde_json::from_str::<WorkLimits>(r#"{"dynamic_events":1000001,"numeric_units":0}"#)
+            .is_err()
+    );
+}
+
+#[test]
+fn exact_accounting_boundary_and_terminal_failure_are_stable() {
+    // One-word addition: three products at 2, one sum at 2,
+    // normalization at 67 => 75 logical numeric units.
+    let mut work = WorkMeter::new(WorkLimits::new(4, 75).unwrap());
+    assert_fraction(&exact(1, 2).add(&exact(1, 3), &mut work).unwrap(), 5, 6);
+    assert_eq!(work.usage().numeric_units, 75);
+    assert!(work.exhaustion().is_none());
+    let first = Exact::from_integer(1).negated(&mut work).unwrap_err();
+    let at_failure = work.usage();
+    assert_eq!(
+        work.exhaustion().unwrap(),
+        &WorkExhaustion {
+            resource: WorkResource::NumericUnits,
+            used: 75,
+            requested: 3,
+            limit: 75,
+            site: WorkSite::Numeric(NumericOperation::Negate),
+        }
+    );
+    assert_eq!(work.visit(EvaluationStep::Target).unwrap_err(), first);
+    assert_eq!(
+        Exact::from_integer(1)
+            .divide(&Exact::from_integer(0), &mut work)
+            .unwrap_err(),
+        first
+    );
+    assert_eq!(
+        work.numeric(NumericOperation::Compare, 0).unwrap_err(),
+        first
+    );
+    assert_eq!(work.usage(), at_failure);
+}
+
+#[test]
+fn zero_cost_and_maximum_reservation_do_not_underflow_or_reactivate() {
+    let mut work = WorkMeter::new(WorkLimits::new(0, 0).unwrap());
+    work.numeric(NumericOperation::Compare, 0).unwrap();
+    let failure = work
+        .numeric(NumericOperation::Multiply, u64::MAX)
+        .unwrap_err();
+    assert!(failure.is_terminal_work_exhaustion());
+    assert_eq!(work.usage(), WorkUsage::default());
+    assert_eq!(
+        work.numeric(NumericOperation::Compare, 0).unwrap_err(),
+        failure
+    );
+    let mut dynamic = WorkMeter::new(WorkLimits::new(0, 5).unwrap());
+    assert!(dynamic.visit(EvaluationStep::Target).is_err());
+    assert_eq!(dynamic.usage(), WorkUsage::default());
+}
+
+#[test]
+fn multiple_targets_share_one_aggregate_meter() {
+    let mut work = WorkMeter::new(WorkLimits::new(3, 50).unwrap());
+    work.visit(EvaluationStep::Target).unwrap();
+    work.visit(EvaluationStep::Expression).unwrap();
+    work.visit(EvaluationStep::Target).unwrap();
+    let failure = work.visit(EvaluationStep::Expression).unwrap_err();
+    assert!(failure.is_terminal_work_exhaustion());
+    assert_eq!(work.usage().dynamic_events, 3);
+}
+
+// A direct bounded call-tree workload, not an expression interpreter/dialect.
+fn expanded_calls(
+    depth: u8,
+    x: u64,
+    work: &mut WorkMeter,
+    entered: &mut u64,
+) -> Result<u64, NumericError> {
+    work.visit(EvaluationStep::CalculationEntry)?;
+    *entered += 1;
+    if depth == 0 {
+        return Ok(x);
+    }
+    let left = expanded_calls(depth - 1, 2 * x, work, entered)?;
+    let right = expanded_calls(depth - 1, 2 * x + 1, work, entered)?;
+    Ok(left + right)
+}
+
+#[test]
+fn c1_expanded_call_witness_terminates_at_dynamic_limit() {
+    let mut work = WorkMeter::new(WorkLimits::new(10_000, 0).unwrap());
+    let mut entered = 0;
+    let failure = expanded_calls(30, 0, &mut work, &mut entered).unwrap_err();
+    assert!(failure.is_terminal_work_exhaustion());
+    assert_eq!(entered, 10_000);
+    assert_eq!(work.usage().dynamic_events, 10_000);
+    assert_eq!(
+        work.exhaustion().unwrap().site,
+        WorkSite::Evaluation(EvaluationStep::CalculationEntry)
+    );
+    // Nearby finite control: 63 invocations, leaves 0..31, sum 496.
+    let mut bounded = WorkMeter::new(WorkLimits::new(63, 0).unwrap());
+    let mut entered = 0;
+    assert_eq!(
+        expanded_calls(5, 0, &mut bounded, &mut entered).unwrap(),
+        496
+    );
+    assert_eq!(entered, 63);
+    assert!(bounded.exhaustion().is_none());
+}
+
+fn dim(value: [i16; 7]) -> Dimension {
+    Dimension::new(value).unwrap()
+}
+
+fn linear(key: &str, dimension: Dimension) -> ResolvedKind<String> {
+    ResolvedKind::linear(key.to_owned(), dimension)
+}
+
+fn named(n: i64, kind: &ResolvedKind<String>) -> NumericValue<String> {
+    NumericValue::new(NumericType::Named(kind.clone()), Exact::from_integer(n))
+}
+
+#[test]
+fn dimensions_use_checked_seven_axis_integer_algebra() {
+    let length = dim([1, 0, 0, 0, 0, 0, 0]);
+    let mass = dim([0, 1, 0, 0, 0, 0, 0]);
+    let time = dim([0, 0, 1, 0, 0, 0, 0]);
+    assert_eq!(
+        mass.checked_product(length)
+            .unwrap()
+            .checked_quotient(time.checked_power(2).unwrap())
+            .unwrap(),
+        dim([1, 1, -2, 0, 0, 0, 0])
+    );
+    assert!(time.checked_quotient(time).unwrap().is_dimensionless());
+    assert!(matches!(
+        dim([32, 0, 0, 0, 0, 0, 0]).checked_product(length),
+        Err(NumericError::DimensionExponent {
+            axis: DimensionAxis::Length,
+            value: 33
+        })
+    ));
+    assert!(dim([0, 0, -32, 0, 0, 0, 0]).checked_quotient(time).is_err());
+    assert!(length.checked_power(i8::MIN).is_err());
+    assert!(Dimension::new([33, 0, 0, 0, 0, 0, 0]).is_err());
+    assert_eq!(
+        serde_json::to_value(time).unwrap(),
+        serde_json::json!([0, 0, 1, 0, 0, 0, 0])
+    );
+    for invalid in ["[0,0,33,0,0,0,0]", "[0,0,1]", "[0,0,1,0,0,0,0,0]"] {
+        assert!(serde_json::from_str::<Dimension>(invalid).is_err());
+    }
+}
+
+#[test]
+fn duration_unit_coordinates_are_exact_and_nominal() {
+    let duration = linear("duration", dim([0, 0, 1, 0, 0, 0, 0]));
+    let s = Unit::new(duration.clone(), source("1"), source("0")).unwrap();
+    let ms = Unit::new(duration.clone(), source("0.001"), source("0")).unwrap();
+    assert_fraction(&ms.convert(&source("750"), &s, &mut meter()).unwrap(), 3, 4);
+    let receive = NumericValue::from_unit(&source("750"), &ms, &mut meter()).unwrap();
+    let dispatch = NumericValue::from_unit(&source("1"), &s, &mut meter()).unwrap();
+    let total = receive.add(&dispatch, &mut meter()).unwrap();
+    assert_fraction(total.coordinate(), 7, 4);
+    assert_fraction(&total.display_in(&ms, &mut meter()).unwrap(), 1750, 1);
+    let different = Unit::new(
+        linear("different-kind", duration.dimension()),
+        source("1"),
+        source("0"),
+    )
+    .unwrap();
+    assert_eq!(
+        ms.convert(&source("750"), &different, &mut meter()),
+        Err(NumericError::IncompatibleTypes)
+    );
+    let inconsistent = Unit::new(
+        linear("duration", dim([1, 0, 0, 0, 0, 0, 0])),
+        source("1"),
+        source("0"),
+    )
+    .unwrap();
+    assert!(
+        ms.convert(&source("1"), &inconsistent, &mut meter())
+            .is_err()
+    );
+    assert!(Unit::new(duration.clone(), source("0"), source("0")).is_err());
+    assert!(Unit::new(duration.clone(), source("ratio(-1,1)"), source("0")).is_err());
+    assert_eq!(
+        Unit::new(duration, source("1"), source("1")).unwrap_err(),
+        NumericError::LinearOffset
+    );
+}
+
+#[test]
+fn affine_point_and_difference_arithmetic_has_distinct_kinds() {
+    let interval = linear("temperature-difference", dim([0, 0, 0, 0, 1, 0, 0]));
+    let point = ResolvedKind::affine("temperature-point".to_owned(), &interval).unwrap();
+    let celsius = Unit::new(point.clone(), source("1"), source("273.15")).unwrap();
+    let fahrenheit = Unit::new(
+        point.clone(),
+        source("ratio(5,9)"),
+        source("ratio(45967,180)"),
+    )
+    .unwrap();
+    let kelvin_interval = Unit::new(interval.clone(), source("1"), source("0")).unwrap();
+    assert_fraction(
+        &celsius
+            .convert(&source("0"), &fahrenheit, &mut meter())
+            .unwrap(),
+        32,
+        1,
+    );
+    assert_fraction(
+        &fahrenheit
+            .convert(&source("70"), &celsius, &mut meter())
+            .unwrap(),
+        190,
+        9,
+    );
+    let p20 = NumericValue::from_unit(&source("20"), &celsius, &mut meter()).unwrap();
+    let p10 = NumericValue::from_unit(&source("10"), &celsius, &mut meter()).unwrap();
+    let difference = p20.subtract(&p10, &mut meter()).unwrap();
+    assert_eq!(
+        difference.value_type(),
+        &NumericType::Named(interval.clone())
+    );
+    assert_fraction(
+        &difference
+            .display_in(&kelvin_interval, &mut meter())
+            .unwrap(),
+        10,
+        1,
+    );
+    let delta5 = named(5, &interval);
+    let p25 = p20.add(&delta5, &mut meter()).unwrap();
+    assert_fraction(&p25.display_in(&celsius, &mut meter()).unwrap(), 25, 1);
+    assert_eq!(delta5.add(&p20, &mut meter()).unwrap(), p25);
+    assert!(p20.add(&p10, &mut meter()).is_err());
+    assert!(delta5.subtract(&p20, &mut meter()).is_err());
+    assert_eq!(
+        p20.power(1, &mut meter()),
+        Err(NumericError::AffineOperation)
+    );
+    assert_eq!(
+        p20.negated(&mut meter()),
+        Err(NumericError::AffineOperation)
+    );
+    assert_eq!(p20.compare(&p10, &mut meter()).unwrap(), Ordering::Greater);
+    assert!(p20.display_in(&kelvin_interval, &mut meter()).is_err());
+    assert!(ResolvedKind::affine(interval.key().clone(), &interval).is_err());
+    assert!(ResolvedKind::affine("other".to_owned(), &point).is_err());
+}
+
+#[test]
+fn affine_conversion_rejects_a_wider_stage_even_when_the_final_value_would_fit() {
+    // A fused coordinate calculation 2*m-m equals m, where m=2^4095 fits.
+    // The fixed multiply stage produces 2^4096, so it must fail before offset
+    // cancellation. The inverse path likewise rejects (m-(-m))/2 at subtraction.
+    let large = BigInt::one() << 4095_usize;
+    let magnitude = exact(&large, 1);
+    let interval = linear("temperature-interval", dim([0, 0, 0, 0, 1, 0, 0]));
+    let point = ResolvedKind::affine("temperature-point".to_owned(), &interval).unwrap();
+    let unit = Unit::new(point, Exact::from_integer(2), exact(-&large, 1)).unwrap();
+    let mut work = meter();
+    for outcome in [
+        unit.to_canonical(&magnitude, &mut work),
+        unit.from_canonical(&magnitude, &mut work),
+    ] {
+        assert!(matches!(
+            outcome,
+            Err(NumericError::Limit(NumericLimit::Bits {
+                component: NumberComponent::Numerator,
+                bits: 4097,
+                limit: MAX_COMPONENT_BITS,
+                ..
+            }))
+        ));
+    }
+    assert!(work.exhaustion().is_none());
+    let half = exact(&large >> 1_usize, 1);
+    assert_fraction(&unit.to_canonical(&half, &mut work).unwrap(), 0, 1);
+    assert_eq!(
+        unit.from_canonical(&Exact::from_integer(0), &mut work)
+            .unwrap(),
+        half
+    );
+}
+
+#[test]
+fn r6_anonymous_compound_energy_needs_one_outer_assertion() {
+    let force = linear("force", dim([1, 1, -2, 0, 0, 0, 0]));
+    let length = linear("length", dim([1, 0, 0, 0, 0, 0, 0]));
+    let energy = linear("energy", dim([2, 1, -2, 0, 0, 0, 0]));
+    let a = named(3, &force)
+        .multiply(&named(4, &length), &mut meter())
+        .unwrap();
+    let b = named(2, &force)
+        .multiply(&named(7, &length), &mut meter())
+        .unwrap();
+    assert_eq!(a.value_type(), &NumericType::Anonymous(energy.dimension()));
+    let sum = a.add(&b, &mut meter()).unwrap();
+    let result = sum.as_kind(&energy, &mut meter()).unwrap();
+    assert_fraction(result.coordinate(), 26, 1);
+    assert_eq!(result.value_type(), &NumericType::Named(energy.clone()));
+    assert_eq!(a.compare(&b, &mut meter()).unwrap(), Ordering::Less);
+    assert!(result.add(&sum, &mut meter()).is_err());
+    assert_eq!(
+        result.as_kind(&energy, &mut meter()),
+        Err(NumericError::KindAssertion)
+    );
+}
+
+#[test]
+fn anonymous_product_then_quotient_closes_and_preserves_scaling() {
+    let mass = linear("mass", dim([0, 1, 0, 0, 0, 0, 0]));
+    let length = linear("length", dim([1, 0, 0, 0, 0, 0, 0]));
+    let time = linear("duration", dim([0, 0, 1, 0, 0, 0, 0]));
+    let momentum = linear("momentum", dim([1, 1, -1, 0, 0, 0, 0]));
+    let result = named(2, &mass)
+        .multiply(&named(3, &length), &mut meter())
+        .unwrap()
+        .divide(&named(2, &time), &mut meter())
+        .unwrap()
+        .as_kind(&momentum, &mut meter())
+        .unwrap();
+    assert_fraction(result.coordinate(), 3, 1);
+    let scalar = NumericValue::number(source("2"));
+    let scaled = scalar.multiply(&named(3, &time), &mut meter()).unwrap();
+    assert_eq!(scaled.value_type(), &NumericType::Named(time.clone()));
+    assert_fraction(scaled.coordinate(), 6, 1);
+    assert_eq!(
+        named(3, &time)
+            .divide(&scalar, &mut meter())
+            .unwrap()
+            .value_type(),
+        &NumericType::Named(time.clone())
+    );
+    assert_eq!(
+        scalar
+            .divide(&named(3, &time), &mut meter())
+            .unwrap()
+            .value_type(),
+        &NumericType::Anonymous(dim([0, 0, -1, 0, 0, 0, 0]))
+    );
+}
+
+#[test]
+fn nominal_kinds_survive_comparison_but_explicit_quotients_can_erase_dimension() {
+    let energy = linear("energy", dim([2, 1, -2, 0, 0, 0, 0]));
+    let torque = linear("torque", energy.dimension());
+    let left = named(7, &energy);
+    let right = named(7, &torque);
+    assert!(left.add(&right, &mut meter()).is_err());
+    assert!(left.compare(&right, &mut meter()).is_err());
+    let ratio = left.divide(&right, &mut meter()).unwrap();
+    assert_eq!(ratio.value_type(), &NumericType::Number);
+    assert_fraction(ratio.coordinate(), 1, 1);
+    let named_ratio = linear("chosen-ratio", Dimension::ZERO);
+    let asserted = ratio.as_kind(&named_ratio, &mut meter()).unwrap();
+    assert_eq!(
+        asserted.value_type(),
+        &NumericType::Named(named_ratio.clone())
+    );
+    assert!(asserted.add(&ratio, &mut meter()).is_err());
+    assert_eq!(
+        NumericValue::<String>::new(NumericType::Anonymous(Dimension::ZERO), source("1")),
+        NumericValue::number(source("1"))
+    );
+}
+
+#[test]
+fn numerical_power_types_and_dimension_overflow_are_checked() {
+    let length = linear("length", dim([1, 0, 0, 0, 0, 0, 0]));
+    let value = named(2, &length);
+    assert_eq!(
+        value.power(0, &mut meter()).unwrap().value_type(),
+        &NumericType::Number
+    );
+    assert_eq!(
+        value.power(1, &mut meter()).unwrap().value_type(),
+        value.value_type()
+    );
+    assert_eq!(
+        value.power(-2, &mut meter()).unwrap().value_type(),
+        &NumericType::Anonymous(dim([-2, 0, 0, 0, 0, 0, 0]))
+    );
+    let large_dimension = linear("large-dimension", dim([32, 0, 0, 0, 0, 0, 0]));
+    assert!(
+        named(1, &large_dimension)
+            .multiply(&value, &mut meter())
+            .is_err()
+    );
+    assert!(named(1, &large_dimension).power(2, &mut meter()).is_err());
+}

crates/oa-core/src/demo.rs

@@ -81,6 +81,7 @@ fn diagram(
             projection,
             view_options: Default::default(),
             nodes: BTreeMap::new(),
+            layout: None,
             routes: vec![],
         },
     );

crates/oa-core/src/language.rs

@@ -3,6 +3,8 @@
 mod semantic_source;
 #[path = "migration_v2/source.rs"]
 mod v2_source;
+pub(crate) use crate::source_defaults::Mode as DeclarationFormat;
+use crate::source_defaults::{self, Context as DefaultContext};
 use crate::*;
 use serde_json::{Map, Value};
 use std::{collections::BTreeMap, fmt};
@@ -142,12 +144,87 @@ pub struct Analysis {
     pub declarations: Vec<DeclarationSpan>,
 }
 
+/// Check the decoded spelling required by declaration-header UUID clauses.
+/// This is the shared 36-byte/hyphen shape rule, not a hexadecimal parser:
+/// callers must additionally parse the UUID. Uppercase hex and JSON escapes
+/// that decode to this spelling remain accepted. URN/braced/compact forms do not.
+pub fn has_uuid_header_shape(decoded: &str) -> bool {
+    decoded.len() == 36
+        && [8, 13, 18, 23]
+            .into_iter()
+            .all(|index| decoded.as_bytes()[index] == b'-')
+}
+
+/// Budgets for one original source buffer. Policy is caller-owned; these
+/// limits do not change the grammar or perform model admission.
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub struct OutlineLimits {
+    pub max_source_bytes: usize,
+    pub max_tokens: usize,
+    pub max_declarations: usize,
+}
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub enum OutlineResource {
+    SourceBytes,
+    Tokens,
+    Declarations,
+}
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub struct OutlineLimit {
+    pub resource: OutlineResource,
+    pub limit: usize,
+    pub observed_at_least: usize,
+    /// Original byte offset where admission stopped; never a rewritten offset.
+    pub offset: usize,
+}
+
+/// Roles discovered by the existing tolerant declaration walk. Keeping the
+/// wrapper preserves DeclarationSpan and Analysis as existing public APIs.
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub struct OutlineDeclaration {
+    pub declaration: DeclarationSpan,
+    pub kind_span: Span,
+    pub alias_span: Span,
+    /// Whole quoted header ID token, even if it is not a valid UUID. In that
+    /// case declaration.id is None. Missing/non-string ID values have no span.
+    pub id_literal_span: Option<Span>,
+}
+
+/// A full-file tolerant scan, not a successful parse or validated model. Invalid
+/// text remains available. Lexical errors and unmatched braces are facts only:
+/// their absence does not establish syntactic or semantic validity.
+///
+/// A budget failure returns Err and no partial Outline. Include reachability,
+/// project completeness and editor revision are intentionally not inferred here.
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub struct Outline<'a> {
+    pub source: &'a str,
+    pub tokens: Vec<TokenSpan>,
+    pub declarations: Vec<OutlineDeclaration>,
+    pub has_lexical_errors: bool,
+    pub has_unmatched_braces: bool,
+}
+
 /// Tolerant highlighting tokens cover the whole input, including incomplete
 /// strings and unexpected characters. No model is created or modified.
 pub fn tokenize(source: &str) -> Vec<TokenSpan> {
+    tokenize_with_limit(source, usize::MAX).expect("unlimited token scan")
+}
+
+fn tokenize_with_limit(source: &str, max_tokens: usize) -> Result<Vec<TokenSpan>, OutlineLimit> {
     let mut tokens = Vec::new();
     let mut cursor = 0;
     while cursor < source.len() {
+        if tokens.len() == max_tokens {
+            return Err(OutlineLimit {
+                resource: OutlineResource::Tokens,
+                limit: max_tokens,
+                observed_at_least: tokens.len().saturating_add(1),
+                offset: cursor,
+            });
+        }
         let start = cursor;
         let ch = source[cursor..].chars().next().expect("in bounds");
         let class = if matches!(ch, ' ' | '\t' | '\r' | '\n') {
@@ -224,7 +301,7 @@ pub fn tokenize(source: &str) -> Vec<TokenSpan> {
             span: Span { start, end: cursor },
         });
     }
-    tokens
+    Ok(tokens)
 }
 
 pub fn lint(source: &str) -> Vec<Diagnostic> {
@@ -570,25 +647,34 @@ fn offset_for(source: &str, line: usize, column: usize) -> usize {
     source.len()
 }
 
-/// Canonical output uses persistent aliases and explicit identities. Typed
-/// nested records are ordinary language fields; JSON documents are not embedded.
+/// Canonical output uses persistent aliases and explicit identities, omitting
+/// only values supplied by source defaults. Typed nested records are ordinary
+/// language fields; JSON documents are not embedded.
 pub fn format(project: &Project) -> String {
     let mut out = std::format!(
-        "arcadia {SCHEMA_VERSION};\nproject {} {} id \"{}\" {{\n    description {};\n\n",
+        "arcadia {SCHEMA_VERSION};\nproject {} {} id \"{}\" {{\n",
         project.alias,
         quote(&project.name),
         project.id,
-        quote(&project.description)
     );
-    for (_, declaration) in format_declarations(project) {
+    if !project.description.is_empty() {
+        out.push_str(&std::format!(
+            "    description {};\n",
+            quote(&project.description)
+        ));
+    }
+    out.push('\n');
+    for (_, declaration) in format_declarations(project, DeclarationFormat::Compact) {
         out.push_str(&declaration);
     }
     out.push_str("}\n");
     out
 }
 
-/// The same typed declaration writer is used by flat and modular source output.
-pub(crate) fn format_declarations(project: &Project) -> Vec<(Id, String)> {
+/// Shared typed writer for canonical output and lossless editing. Complete edit
+/// comparisons retain defaults; emitted declarations and value fragments apply
+/// only the omission rules valid in their selected source context.
+pub(crate) fn format_declarations(project: &Project, mode: DeclarationFormat) -> Vec<(Id, String)> {
     let aliases = project
         .identities()
         .into_iter()
@@ -600,6 +686,7 @@ pub(crate) fn format_declarations(project: &Project) -> Vec<(Id, String)> {
         let mut fields = payload(&serde_json::to_value(&e.body).unwrap());
         fields.insert("description".into(), Value::String(e.description.clone()));
         fields.insert("parent".into(), serde_json::to_value(e.parent).unwrap());
+        let fields = source_defaults::fields(DefaultContext::Element(e.kind()), &fields, mode);
         write_declaration(
             &mut out,
             &element_word(e.kind(), e.layer()),
@@ -615,6 +702,7 @@ pub(crate) fn format_declarations(project: &Project) -> Vec<(Id, String)> {
         let mut out = String::new();
         let mut fields = payload(&serde_json::to_value(&r.body).unwrap());
         fields.insert("description".into(), Value::String(r.description.clone()));
+        let fields = source_defaults::fields(DefaultContext::Relation(r.kind()), &fields, mode);
         write_declaration(
             &mut out,
             &relation_word(r.kind()),
@@ -630,6 +718,7 @@ pub(crate) fn format_declarations(project: &Project) -> Vec<(Id, String)> {
         let mut out = String::new();
         let mut fields = record_fields(d);
         fields.remove("nodes");
+        let fields = source_defaults::fields(DefaultContext::Diagram, &fields, mode);
         write_declaration(
             &mut out,
             "diagram",
@@ -644,6 +733,7 @@ pub(crate) fn format_declarations(project: &Project) -> Vec<(Id, String)> {
             let mut out = String::new();
             let mut fields = record_fields(n);
             fields.insert("diagram".into(), Value::String(d.id.to_string()));
+            let fields = source_defaults::fields(DefaultContext::Node, &fields, mode);
             write_declaration(&mut out, "node", &n.alias, None, n.id, &fields, &aliases);
             declarations.push((n.id, out));
         }
@@ -656,7 +746,7 @@ pub(crate) fn format_declarations(project: &Project) -> Vec<(Id, String)> {
             &a.alias,
             Some(&a.name),
             a.id,
-            &record_fields(a),
+            &source_defaults::fields(DefaultContext::Artifact, &record_fields(a), mode),
             &aliases,
         );
         declarations.push((a.id, out));
@@ -669,7 +759,7 @@ pub(crate) fn format_declarations(project: &Project) -> Vec<(Id, String)> {
             &t.alias,
             Some(&t.name),
             t.id,
-            &record_fields(t),
+            &source_defaults::fields(DefaultContext::Trace, &record_fields(t), mode),
             &aliases,
         );
         declarations.push((t.id, out));
@@ -1230,11 +1320,7 @@ impl Parser<'_> {
         self.cursor += 1;
         let offset = self.current().span.start;
         let value = self.quoted()?;
-        if value.len() != 36
-            || ![8, 13, 18, 23]
-                .into_iter()
-                .all(|i| value.as_bytes()[i] == b'-')
-        {
+        if !has_uuid_header_shape(&value) {
             return Err(Error {
                 code: "invalid_source",
                 offset,
@@ -1671,7 +1757,9 @@ pub(crate) fn resolve_declarations(
                         *viewpoint = ScenarioViewpoint::MixedLegacy;
                     }
                     let mut body = serde_json::to_value(initial).unwrap();
-                    let defaults = if legacy {
+                    let defaults = if project.schema_version >= 7 {
+                        source_defaults::parser_fields(DefaultContext::Element(kind))
+                    } else if legacy {
                         crate::persistence::v3::legacy_defaults(kind)
                             .and_then(|value| value.as_object().cloned())
                             .unwrap_or_else(|| payload(&body))
@@ -1728,7 +1816,12 @@ pub(crate) fn resolve_declarations(
                     let mut body =
                         serde_json::to_value(RelationBody::new(kind, Id::nil(), Id::nil()))
                             .unwrap();
-                    let merged = merge_fields(payload(&body), fields).map_err(&conversion_error)?;
+                    let defaults = if project.schema_version >= 7 {
+                        source_defaults::parser_fields(DefaultContext::Relation(kind))
+                    } else {
+                        payload(&body)
+                    };
+                    let merged = merge_fields(defaults, fields).map_err(&conversion_error)?;
                     replace_payload(&mut body, merged);
                     let body = serde_json::from_value(body)
                         .map_err(|e| conversion_error(e.to_string()))?;
@@ -1753,7 +1846,10 @@ pub(crate) fn resolve_declarations(
                     }
                     let defaults =
                         serde_json::json!({"description":"","layer":"Oa","projection":"Overview","routes":[],"view_options":crate::view_options::ViewOptions::default()});
-                    let mut record = merge_fields(defaults.as_object().unwrap().clone(), fields)
+                    let defaults = if project.schema_version >= 7 {
+                        source_defaults::parser_fields(DefaultContext::Diagram)
+                    } else { defaults.as_object().unwrap().clone() };
+                    let mut record = merge_fields(defaults, fields)
                         .map_err(&conversion_error)?;
                     header(&mut record, d, true);
                     record.insert("nodes".into(), serde_json::json!({}));
@@ -1768,7 +1864,10 @@ pub(crate) fn resolve_declarations(
                         return Err(conversion_error("Missing required field 'element'.".into()));
                     }
                     let defaults = serde_json::json!({"element":null,"position":{"x":0.0,"y":0.0},"size":{"width":224.0,"height":94.0},"collapsed":false,"port_anchors":[]});
-                    let mut record = merge_fields(defaults.as_object().unwrap().clone(), fields)
+                    let defaults = if project.schema_version >= 7 {
+                        source_defaults::parser_fields(DefaultContext::Node)
+                    } else { defaults.as_object().unwrap().clone() };
+                    let mut record = merge_fields(defaults, fields)
                         .map_err(&conversion_error)?;
                     header(&mut record, d, false);
                     let node: NodePlacement = serde_json::from_value(Value::Object(record))
@@ -1780,7 +1879,10 @@ pub(crate) fn resolve_declarations(
                         return Err(conversion_error("Missing required field 'owner'.".into()));
                     }
                     let defaults = serde_json::json!({"description":"","owner":null,"relation":"References","uri":"","revision":null,"fragment":null});
-                    let mut record = merge_fields(defaults.as_object().unwrap().clone(), fields)
+                    let defaults = if project.schema_version >= 7 {
+                        source_defaults::parser_fields(DefaultContext::Artifact)
+                    } else { defaults.as_object().unwrap().clone() };
+                    let mut record = merge_fields(defaults, fields)
                         .map_err(&conversion_error)?;
                     header(&mut record, d, true);
                     let artifact = serde_json::from_value(Value::Object(record))
@@ -1796,7 +1898,10 @@ pub(crate) fn resolve_declarations(
                         }
                     }
                     let defaults = serde_json::json!({"description":"","oa":null,"sa":null,"kind":"Refinement","baseline":null});
-                    let mut record = merge_fields(defaults.as_object().unwrap().clone(), fields)
+                    let defaults = if project.schema_version >= 7 {
+                        source_defaults::parser_fields(DefaultContext::Trace)
+                    } else { defaults.as_object().unwrap().clone() };
+                    let mut record = merge_fields(defaults, fields)
                         .map_err(&conversion_error)?;
                     header(&mut record, d, true);
                     let trace = if project.schema_version < 5 {
@@ -1962,8 +2067,49 @@ fn take_required_id(fields: &mut Map<String, Value>, key: &str) -> Result<Id, St
 
 /// Analyze an incomplete source buffer without adopting a candidate. Declaration
 /// spans remain available even when a later declaration contains errors.
+/// Invalid compact/braced/URN header IDs retain no authored identity, matching
+/// the declaration parser rather than the UUID crate's broader accepted forms.
 pub fn analyze(source: &str) -> Analysis {
     let tokens = tokenize(source);
+    let (declarations, _) =
+        declaration_outline(source, &tokens, usize::MAX).expect("unlimited declaration walk");
+    Analysis {
+        tokens,
+        diagnostics: lint(source),
+        declarations: declarations.into_iter().map(|d| d.declaration).collect(),
+    }
+}
+
+/// Read exact current text without lint, parsing a model, stabilization or I/O.
+/// Source bytes are admitted before token allocation; token/declaration limits
+/// are checked before lexing the next token or materializing the next record.
+pub fn outline(source: &str, limits: OutlineLimits) -> Result<Outline<'_>, OutlineLimit> {
+    if source.len() > limits.max_source_bytes {
+        return Err(OutlineLimit {
+            resource: OutlineResource::SourceBytes,
+            limit: limits.max_source_bytes,
+            observed_at_least: source.len(),
+            offset: 0,
+        });
+    }
+    let tokens = tokenize_with_limit(source, limits.max_tokens)?;
+    let has_lexical_errors = tokens.iter().any(|token| token.class == TokenClass::Error);
+    let (declarations, has_unmatched_braces) =
+        declaration_outline(source, &tokens, limits.max_declarations)?;
+    Ok(Outline {
+        source,
+        tokens,
+        declarations,
+        has_lexical_errors,
+        has_unmatched_braces,
+    })
+}
+
+fn declaration_outline(
+    source: &str,
+    tokens: &[TokenSpan],
+    max_declarations: usize,
+) -> Result<(Vec<OutlineDeclaration>, bool), OutlineLimit> {
     let significant = tokens
         .iter()
         .filter(|t| !matches!(t.class, TokenClass::Whitespace | TokenClass::Comment))
@@ -1972,17 +2118,21 @@ pub fn analyze(source: &str) -> Analysis {
     // again would make tolerant navigation quadratic on deeply nested drafts.
     let mut body_ends = vec![None; significant.len()];
     let mut bodies = Vec::new();
+    let mut unmatched_close = false;
     for (index, token) in significant.iter().enumerate() {
         match &source[token.span.start..token.span.end] {
             "{" => bodies.push(index),
             "}" => {
                 if let Some(open) = bodies.pop() {
                     body_ends[open] = Some(token.span.end);
+                } else {
+                    unmatched_close = true;
                 }
             }
             _ => {}
         }
     }
+    let has_unmatched_braces = unmatched_close || !bodies.is_empty();
     let mut declarations = Vec::new();
     for (i, t) in significant.iter().enumerate() {
         let word = &source[t.span.start..t.span.end];
@@ -2007,7 +2157,16 @@ pub fn analyze(source: &str) -> Analysis {
             }
             j += 1;
         }
+        if declarations.len() == max_declarations {
+            return Err(OutlineLimit {
+                resource: OutlineResource::Declarations,
+                limit: max_declarations,
+                observed_at_least: declarations.len().saturating_add(1),
+                offset: t.span.start,
+            });
+        }
         let mut id = None;
+        let mut id_literal_span = None;
         if significant
             .get(j)
             .is_some_and(|t| &source[t.span.start..t.span.end] == "id")
@@ -2015,39 +2174,51 @@ pub fn analyze(source: &str) -> Analysis {
             if let Some(value) = significant.get(j + 1)
                 && value.class == TokenClass::String
             {
+                id_literal_span = Some(value.span);
                 let text =
                     serde_json::from_str::<String>(&source[value.span.start..value.span.end])
                         .unwrap();
-                id = Id::parse_str(&text).ok();
+                if has_uuid_header_shape(&text) {
+                    id = Id::parse_str(&text).ok();
+                }
             }
             j += 2;
         }
-        let mut end = significant
-            .get(j)
-            .map_or(alias_token.span.end, |t| t.span.end);
+        // A recognized header ID at EOF must remain inside the whole span.
+        // Keep the old next-token/body behavior; only the EOF fallback changes.
+        let header_end = significant
+            .get(j.saturating_sub(1))
+            .or_else(|| significant.last())
+            .map_or(alias_token.span.end, |token| token.span.end);
+        let mut end = significant.get(j).map_or(header_end, |t| t.span.end);
         if significant
             .get(j)
             .is_some_and(|t| &source[t.span.start..t.span.end] == "{")
         {
             end = body_ends[j].unwrap_or(source.len());
         }
-        declarations.push(DeclarationSpan {
-            alias: alias.into(),
-            id,
-            kind: word.into(),
-            span: Span {
-                start: t.span.start,
-                end,
+        declarations.push(OutlineDeclaration {
+            declaration: DeclarationSpan {
+                alias: alias.into(),
+                id,
+                kind: word.into(),
+                span: Span {
+                    start: t.span.start,
+                    end,
+                },
             },
+            kind_span: t.span,
+            alias_span: alias_token.span,
+            id_literal_span,
         });
     }
-    Analysis {
-        tokens,
-        diagnostics: lint(source),
-        declarations,
-    }
+    Ok((declarations, has_unmatched_braces))
 }
 
+#[cfg(test)]
+#[path = "language_outline_tests.rs"]
+mod outline_tests;
+
 #[cfg(test)]
 #[path = "language_nesting_tests.rs"]
 mod nesting_tests;
@@ -2442,11 +2613,7 @@ pub(crate) mod legacy {
             let value = self.quoted()?;
             // Require the portable 8-4-4-4-12 spelling, not the UUID crate's URN,
             // braces, or compact alternatives. Uppercase hexadecimal is accepted.
-            if value.len() != 36
-                || ![8, 13, 18, 23]
-                    .into_iter()
-                    .all(|index| value.as_bytes()[index] == b'-')
-            {
+            if !super::has_uuid_header_shape(&value) {
                 return Err(Error {
                     code: "invalid_source",
                     offset,

crates/oa-core/src/language_outline_tests.rs

@@ -0,0 +1,386 @@
+//! Prepared outline tests. Explicit compatibility tests additionally exercise
+//! the existing parsers/analyze; the outline entry itself never calls them.
+use super::*;
+
+fn limits() -> OutlineLimits {
+    OutlineLimits {
+        max_source_bytes: 1024 * 1024,
+        max_tokens: 100_000,
+        max_declarations: 1_000,
+    }
+}
+
+fn declaration<'a>(result: &'a Outline<'_>, alias: &str) -> &'a OutlineDeclaration {
+    result
+        .declarations
+        .iter()
+        .find(|d| d.declaration.alias == alias)
+        .unwrap()
+}
+
+fn text(source: &str, span: Span) -> &str {
+    &source[span.start..span.end]
+}
+
+#[test]
+fn outline_roles_preserve_unicode_crlf_and_exact_escaped_uuid_literal() {
+    let source = "// 検査 🚒\r\noa_actor responder \"救助\" id \"\\u00300000000-0000-0000-0000-000000000001\" {}\r\nsource @ // 使用\r\n responder;";
+    let before = source.as_bytes().to_vec();
+    let result = outline(source, limits()).unwrap();
+    assert_eq!(result.source.as_bytes(), before);
+    assert_eq!(result.source.as_ptr(), source.as_ptr());
+    let d = declaration(&result, "responder");
+    assert_eq!(text(source, d.kind_span), "oa_actor");
+    assert_eq!(text(source, d.alias_span), "responder");
+    assert_eq!(
+        text(source, d.id_literal_span.unwrap()),
+        "\"\\u00300000000-0000-0000-0000-000000000001\""
+    );
+    assert_eq!(d.declaration.id, Some(Id::from_u128(1)));
+    assert_eq!(d.declaration.span.start, source.find("oa_actor").unwrap());
+    assert_eq!(d.declaration.span.end, source.find("{}\r\n").unwrap() + 2);
+    let mut end = 0;
+    for token in &result.tokens {
+        assert_eq!(token.span.start, end);
+        assert!(token.span.start < token.span.end);
+        assert!(source.is_char_boundary(token.span.start));
+        assert!(source.is_char_boundary(token.span.end));
+        end = token.span.end;
+    }
+    assert_eq!(end, source.len());
+    assert!(!result.has_lexical_errors);
+    assert!(!result.has_unmatched_braces);
+}
+
+#[test]
+fn closed_id_at_eof_is_inside_the_declaration_extent() {
+    for source in [
+        "oa_actor a \"Actor\" id \"00000000-0000-0000-0000-000000000001\"",
+        "node placed id \"00000000-0000-0000-0000-000000000001\"",
+    ] {
+        let result = outline(source, limits()).unwrap();
+        let d = &result.declarations[0];
+        let literal = d.id_literal_span.unwrap();
+        assert_eq!(d.declaration.id, Some(Id::from_u128(1)));
+        assert_eq!(d.declaration.span.end, source.len());
+        assert!(d.declaration.span.start <= literal.start);
+        assert!(literal.end <= d.declaration.span.end);
+    }
+    for source in ["oa_actor a \"Actor\"", "oa_actor a \"Actor\" id"] {
+        let result = outline(source, limits()).unwrap();
+        let d = &result.declarations[0];
+        assert_eq!(d.declaration.span.end, source.len());
+        assert_eq!(d.declaration.id, None);
+        assert_eq!(d.id_literal_span, None);
+    }
+}
+
+#[test]
+fn missing_bad_and_historical_ids_never_allocate_authored_identity() {
+    let source = "oa_actor missing \"No ID\" {}\noa_actor bad \"Bad ID\" id \"not-a-uuid\" {}\noa_actor historical \"00000000-0000-0000-0000-000000000001\" { history uuid \"00000000-0000-0000-0000-000000000001\"; }";
+    let first = outline(source, limits()).unwrap();
+    let second = outline(source, limits()).unwrap();
+    assert_eq!(first, second);
+    assert!(
+        first
+            .declarations
+            .iter()
+            .all(|d| d.declaration.id.is_none())
+    );
+    assert_eq!(declaration(&first, "missing").id_literal_span, None);
+    assert_eq!(declaration(&first, "historical").id_literal_span, None);
+    assert_eq!(
+        text(source, declaration(&first, "bad").id_literal_span.unwrap()),
+        "\"not-a-uuid\""
+    );
+    // Balanced tokens are not a successful syntax/semantic validation claim.
+    assert!(!first.has_lexical_errors);
+    assert!(!first.has_unmatched_braces);
+}
+
+#[test]
+fn invalid_full_scan_keeps_closed_children_and_reports_lexical_body_facts() {
+    let source = "oa_entity outer \"Outer\" {\n oa_actor ready \"Ready\" { description \"} stays text\"; }\n oa_actor pending \"Pending\" { description \"unfinished 🌊";
+    let result = outline(source, limits()).unwrap();
+    assert_eq!(result.source, source);
+    assert_eq!(result.tokens.last().unwrap().span.end, source.len());
+    assert!(result.has_lexical_errors);
+    assert!(result.has_unmatched_braces);
+    let ready = declaration(&result, "ready");
+    assert_eq!(
+        text(source, ready.declaration.span),
+        "oa_actor ready \"Ready\" { description \"} stays text\"; }"
+    );
+    assert_eq!(
+        declaration(&result, "outer").declaration.span.end,
+        source.len()
+    );
+    assert_eq!(
+        declaration(&result, "pending").declaration.span.end,
+        source.len()
+    );
+    let unmatched_close = outline("}\n// brace in comment {\n", limits()).unwrap();
+    assert!(unmatched_close.has_unmatched_braces);
+    assert!(!unmatched_close.has_lexical_errors);
+}
+
+#[test]
+fn missing_body_syntax_is_unchecked_even_when_known_error_flags_are_clear() {
+    let source = "oa_actor a \"A\" id \"00000000-0000-0000-0000-000000000001\"";
+    let result = outline(source, limits()).unwrap();
+    assert_eq!(result.declarations.len(), 1);
+    assert!(!result.has_lexical_errors);
+    assert!(!result.has_unmatched_braces);
+    // There is deliberately no `valid` flag: the known-complete fact is scanning
+    // these bytes, not the missing body becoming legal or the draft being applied.
+    assert_eq!(result.source, source);
+}
+
+#[test]
+fn keyword_alias_and_collisions_keep_every_source_ordered_header() {
+    let source = "project root_model \"Model\" {\n oa_actor oa_activity \"First\" id \"00000000-0000-0000-0000-000000000001\" {}\n oa_actor oa_activity \"Second\" id \"00000000-0000-0000-0000-000000000001\" {}\n diagram view_one \"View\" {}\n node placement { diagram @view_one; }\n}";
+    let result = outline(source, limits()).unwrap();
+    assert_eq!(result.declarations.len(), 5);
+    let duplicates: Vec<_> = result
+        .declarations
+        .iter()
+        .filter(|d| d.declaration.alias == "oa_activity")
+        .collect();
+    assert_eq!(duplicates.len(), 2);
+    assert!(duplicates[0].alias_span.start < duplicates[1].alias_span.start);
+    assert_eq!(duplicates[0].declaration.id, duplicates[1].declaration.id);
+    assert!(
+        result
+            .tokens
+            .iter()
+            .any(|t| t.span == duplicates[0].alias_span && t.class == TokenClass::Keyword)
+    );
+    assert_eq!(
+        text(source, declaration(&result, "placement").kind_span),
+        "node"
+    );
+    assert_eq!(declaration(&result, "placement").declaration.id, None);
+}
+
+#[test]
+fn bounds_refuse_before_returning_a_partial_outline() {
+    let source = "oa_actor a \"A\" {}\noa_actor b \"B\" {}";
+    let admitted = outline(source, limits()).unwrap();
+    let exact = OutlineLimits {
+        max_source_bytes: source.len(),
+        max_tokens: admitted.tokens.len(),
+        max_declarations: 2,
+    };
+    assert_eq!(outline(source, exact).unwrap(), admitted);
+    for resource in [
+        OutlineResource::SourceBytes,
+        OutlineResource::Tokens,
+        OutlineResource::Declarations,
+    ] {
+        let mut lower = exact;
+        match resource {
+            OutlineResource::SourceBytes => lower.max_source_bytes -= 1,
+            OutlineResource::Tokens => lower.max_tokens -= 1,
+            OutlineResource::Declarations => lower.max_declarations -= 1,
+        }
+        let error = outline(source, lower).unwrap_err();
+        assert_eq!(error.resource, resource);
+        assert!(error.observed_at_least > error.limit);
+        assert!(source.is_char_boundary(error.offset));
+        if resource == OutlineResource::Declarations {
+            assert_eq!(error.offset, source.find("oa_actor b").unwrap());
+        }
+    }
+    let empty = outline(
+        "",
+        OutlineLimits {
+            max_source_bytes: 0,
+            max_tokens: 0,
+            max_declarations: 0,
+        },
+    )
+    .unwrap();
+    assert!(empty.tokens.is_empty() && empty.declarations.is_empty());
+    let unicode = "// 🌊\r\noa_actor a \"A\" {}";
+    let error = outline(
+        unicode,
+        OutlineLimits {
+            max_source_bytes: 4,
+            ..limits()
+        },
+    )
+    .unwrap_err();
+    assert_eq!(error.resource, OutlineResource::SourceBytes);
+    assert_eq!(error.offset, 0);
+    let error = outline(
+        unicode,
+        OutlineLimits {
+            max_tokens: 1,
+            ..limits()
+        },
+    )
+    .unwrap_err();
+    assert_eq!(error.resource, OutlineResource::Tokens);
+    assert_eq!(error.offset, unicode.find('\n').unwrap());
+}
+
+#[test]
+fn outline_ranges_follow_current_bytes_without_identity_stabilization() {
+    let old = "oa_actor a \"A\" {}\nsource @a;";
+    let current = format!("// 航海 🚒\r\n{old}");
+    let old_outline = outline(old, limits()).unwrap();
+    let current_outline = outline(&current, limits()).unwrap();
+    let shift = current.len() - old.len();
+    let old_role = &old_outline.declarations[0];
+    let current_role = &current_outline.declarations[0];
+    assert_eq!(
+        current_role.alias_span.start,
+        old_role.alias_span.start + shift
+    );
+    assert_eq!(
+        current_role.kind_span.start,
+        old_role.kind_span.start + shift
+    );
+    assert_eq!(
+        current_role.declaration.span.end,
+        old_role.declaration.span.end + shift
+    );
+    assert_eq!(current_outline.source, current);
+    assert_eq!(old_outline.source, old);
+    assert_eq!(current_role.declaration.id, None);
+    assert!(!current_outline.source.contains(" id "));
+    // Workspace revision/stale-handle rejection belongs to the query/adapter,
+    // not a claim that an old owned span can be applied to any other string.
+}
+
+#[test]
+fn deeply_nested_bounds_use_the_same_iterative_walk_and_declaration_budget() {
+    let mut source = String::new();
+    for index in 0..600 {
+        source.push_str(&format!("oa_activity work_{index} \"Work\" {{\n"));
+    }
+    source.push_str(&"}\n".repeat(600));
+    let result = outline(&source, limits()).unwrap();
+    assert_eq!(result.declarations.len(), 600);
+    assert!(!result.has_unmatched_braces);
+    assert_eq!(
+        result.declarations[0].declaration.span.end,
+        source.len() - 1
+    );
+    let error = outline(
+        &source,
+        OutlineLimits {
+            max_declarations: 599,
+            ..limits()
+        },
+    )
+    .unwrap_err();
+    assert_eq!(error.resource, OutlineResource::Declarations);
+    assert_eq!(error.observed_at_least, 600);
+    assert_eq!(error.offset, source.find("oa_activity work_599").unwrap());
+}
+
+#[test]
+fn noncanonical_uuid_spellings_have_no_outline_or_analysis_identity() {
+    for raw in [
+        "00000000000000000000000000000001",
+        "{00000000-0000-0000-0000-000000000001}",
+        "urn:uuid:00000000-0000-0000-0000-000000000001",
+    ] {
+        assert!(
+            Id::parse_str(raw).is_ok(),
+            "The UUID crate alone is too permissive"
+        );
+        assert!(!has_uuid_header_shape(raw));
+        let literal = format!("\"{raw}\"");
+        let modern = format!("arcadia 7; project model \"Model\" id {literal} {{}}");
+        let before = modern.clone();
+        let result = outline(&modern, limits()).unwrap();
+        let d = declaration(&result, "model");
+        assert_eq!(d.declaration.id, None);
+        assert_eq!(text(&modern, d.id_literal_span.unwrap()), literal);
+        assert_eq!(modern, before);
+        let errors = parse(&modern).unwrap_err();
+        assert!(
+            errors
+                .iter()
+                .any(|error| error.message.contains("8-4-4-4-12")
+                    && error.span.start == modern.find(&literal).unwrap())
+        );
+        // Intentional compatibility correction: old analyze yielded Some(Id(1))
+        // here despite lint rejecting the header. It now shares outline's None.
+        let analysis = analyze(&modern);
+        assert_eq!(
+            analysis
+                .declarations
+                .iter()
+                .find(|d| d.alias == "model")
+                .unwrap()
+                .id,
+            None
+        );
+        assert!(
+            analysis
+                .diagnostics
+                .iter()
+                .any(|error| error.message.contains("8-4-4-4-12"))
+        );
+        let legacy_source = format!("arcadia 1; project \"Legacy\" id {literal} {{}}");
+        let legacy_errors = legacy::parse(&legacy_source).unwrap_err();
+        assert!(
+            legacy_errors
+                .iter()
+                .any(|error| error.message.contains("8-4-4-4-12"))
+        );
+    }
+}
+
+#[test]
+fn uppercase_and_json_escaped_header_ids_survive_both_parsers_and_outline() {
+    let expected = Id::from_u128(0xabcdef);
+    let canonical = expected.to_string();
+    let uppercase = canonical.to_uppercase();
+    assert_ne!(uppercase, canonical);
+    for raw in [uppercase.clone(), format!("\\u0030{}", &uppercase[1..])] {
+        let literal = format!("\"{raw}\"");
+        let decoded: String = serde_json::from_str(&literal).unwrap();
+        assert!(has_uuid_header_shape(&decoded));
+        let modern = format!("arcadia 7; project model \"Model\" id {literal} {{}}");
+        let result = outline(&modern, limits()).unwrap();
+        let d = declaration(&result, "model");
+        assert_eq!(d.declaration.id, Some(expected));
+        assert_eq!(text(&modern, d.id_literal_span.unwrap()), literal);
+        assert_eq!(result.source.as_bytes(), modern.as_bytes());
+        assert_eq!(parse(&modern).unwrap().id, expected);
+        let analysis = analyze(&modern);
+        assert_eq!(analysis.declarations[0].id, Some(expected));
+        assert!(
+            !analysis
+                .diagnostics
+                .iter()
+                .any(|error| error.severity == crate::validation::Severity::Error)
+        );
+        let legacy_source = format!("arcadia 1; project \"Legacy\" id {literal} {{}}");
+        assert_eq!(legacy::parse(&legacy_source).unwrap().id, expected);
+    }
+}
+
+#[test]
+fn header_shape_still_requires_valid_hexadecimal_uuid_data() {
+    let raw = "00000000-0000-0000-0000-00000000000Z";
+    assert!(has_uuid_header_shape(raw));
+    assert!(Id::parse_str(raw).is_err());
+    let literal = format!("\"{raw}\"");
+    let source = format!("arcadia 7; project model \"Model\" id {literal} {{}}");
+    let result = outline(&source, limits()).unwrap();
+    let d = declaration(&result, "model");
+    assert_eq!(d.declaration.id, None);
+    assert_eq!(text(&source, d.id_literal_span.unwrap()), literal);
+    assert!(
+        parse(&source)
+            .unwrap_err()
+            .iter()
+            .any(|error| error.message == "Invalid UUID identity.")
+    );
+    assert_eq!(analyze(&source).declarations[0].id, None);
+}

crates/oa-core/src/lib.rs

@@ -1,4 +1,5 @@
 //! Framework-independent OA/SA model, transactional commands and editing services.
+pub mod analysis_numeric;
 pub mod data;
 pub mod language;
 pub mod model;
@@ -8,8 +9,10 @@ pub mod ports;
 pub mod projection;
 pub mod references;
 pub mod routing;
+pub mod scenario_layout;
 pub mod semantic;
 pub mod session;
+mod source_defaults;
 pub mod source_files;
 pub mod source_project;
 pub mod topology_context;
@@ -18,6 +21,9 @@ pub mod validation;
 pub mod view_options;
 pub use model::*;
 pub use ports::*;
+pub use scenario_layout::{
+    DiagramLayout, ScenarioLanePosition, ScenarioLayout, ScenarioMessagePosition,
+};
 pub use semantic::*;
 pub use session::*;
 mod demo;

crates/oa-core/src/model.rs

@@ -1436,6 +1436,7 @@ pub enum ProjectionKind {
     FunctionalDataflow,
     Capabilities,
     StateMachine { machine: Id },
+    Scenario { scenario: Id },
 }
 impl ProjectionKind {
     pub fn state_machine(self) -> Option<Id> {
@@ -1445,8 +1446,30 @@ impl ProjectionKind {
         }
     }
 
+    /// The semantic owner of a saved Scenario representation.
+    pub fn scenario(self) -> Option<Id> {
+        match self {
+            Self::Scenario { scenario } => Some(scenario),
+            _ => None,
+        }
+    }
+
+    /// Explicitly classify architecture views; absence of a state machine is insufficient.
+    pub fn is_architecture(self) -> bool {
+        match self {
+            Self::Overview
+            | Self::Decomposition
+            | Self::Allocation
+            | Self::Traceability
+            | Self::FunctionalDataflow
+            | Self::Capabilities => true,
+            Self::StateMachine { .. } | Self::Scenario { .. } => false,
+        }
+    }
+
     pub fn includes(self, kind: Kind) -> bool {
         match self {
+            Self::Scenario { .. } => false,
             Self::StateMachine { .. } => {
                 matches!(kind, Kind::StateMachine | Kind::Region) || kind.is_state()
             }
@@ -1471,6 +1494,7 @@ impl std::fmt::Display for ProjectionKind {
     fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
         f.write_str(match self {
             Self::StateMachine { .. } => "State machine",
+            Self::Scenario { .. } => "Scenario",
             Self::Allocation => "Architecture · allocated work",
             Self::FunctionalDataflow => "Functional dataflow",
             Self::Capabilities => "Missions & capabilities",
@@ -1495,6 +1519,8 @@ pub struct Diagram {
     pub nodes: BTreeMap<Id, NodePlacement>,
     #[serde(default)]
     pub routes: Vec<EdgeRoute>,
+    #[serde(default, skip_serializing_if = "Option::is_none")]
+    pub layout: Option<crate::scenario_layout::DiagramLayout>,
 }
 /// Authored presentation for one existing relation or trace in one diagram.
 /// Computed endpoints and automatic routing elbows are never persisted here.
@@ -1502,11 +1528,45 @@ pub struct Diagram {
 #[serde(deny_unknown_fields)]
 pub struct EdgeRoute {
     pub edge: Id,
+    #[serde(default, skip_serializing_if = "Option::is_none")]
+    pub source_attachment: Option<EdgeAttachment>,
+    #[serde(default, skip_serializing_if = "Option::is_none")]
+    pub target_attachment: Option<EdgeAttachment>,
     #[serde(default)]
     pub waypoints: Vec<Position>,
     #[serde(default)]
     pub label: Option<EdgeLabel>,
 }
+
+/// Presentation preference on one end of a connection. Real ports take precedence.
+#[derive(Debug, Clone, Copy, PartialEq, Serialize, Deserialize)]
+#[serde(deny_unknown_fields)]
+pub struct EdgeAttachment {
+    pub side: PortAnchorSide,
+    pub offset: f32,
+}
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub enum EdgeEnd {
+    Source,
+    Target,
+}
+
+impl EdgeRoute {
+    pub fn attachment(&self, end: EdgeEnd) -> Option<EdgeAttachment> {
+        match end {
+            EdgeEnd::Source => self.source_attachment,
+            EdgeEnd::Target => self.target_attachment,
+        }
+    }
+
+    pub fn set_attachment(&mut self, end: EdgeEnd, attachment: Option<EdgeAttachment>) {
+        match end {
+            EdgeEnd::Source => self.source_attachment = attachment,
+            EdgeEnd::Target => self.target_attachment = attachment,
+        }
+    }
+}
 #[derive(Debug, Clone, PartialEq, Serialize, Deserialize)]
 #[serde(deny_unknown_fields)]
 pub struct EdgeLabel {
@@ -1921,6 +1981,7 @@ impl Project {
                 view_options: crate::view_options::ViewOptions::default(),
                 nodes: BTreeMap::new(),
                 routes: vec![],
+                layout: None,
             },
         );
         id

crates/oa-core/src/projection.rs

@@ -278,6 +278,11 @@ fn project_diagram_impl(
     mut availability: Option<&mut BTreeMap<Id, crate::view_options::EdgeAvailability>>,
     index: Option<&crate::view_options::ViewIndex>,
 ) -> ProjectedView {
+    // Saved Scenario layout is not an architecture/state projection. Its dedicated
+    // renderer is not wired yet; never interpret its payload through this fallback.
+    if d.projection.scenario().is_some() {
+        return ProjectedView::default();
+    }
     let parents = parents(p, d);
     let mut nodes = Vec::new();
     for n in d.nodes.values() {
@@ -394,6 +399,7 @@ fn project_diagram_impl(
             continue;
         }
         let included = match d.projection {
+            ProjectionKind::Scenario { .. } => false,
             ProjectionKind::StateMachine { machine } => matches!(&r.body,
                 RelationBody::StateTransition { transition_kind, .. }
                     if *transition_kind != TransitionKind::Internal

crates/oa-core/src/references.rs

@@ -203,7 +203,81 @@ pub fn visit_relation_refs(r: &mut Relation, mut visit: impl FnMut(&mut Id)) {
         _ => {}
     }
 }
-pub fn remap_references(p: &mut Project, old: Id, new: Id) {
+/// Every semantic/presentation reference in a diagram, excluding its own identities.
+pub fn diagram_references(d: &Diagram) -> Vec<Id> {
+    let mut copy = d.clone();
+    let mut refs = Vec::new();
+    visit_diagram_refs(&mut copy, |id| refs.push(*id));
+    refs
+}
+
+pub fn visit_diagram_refs(d: &mut Diagram, mut visit: impl FnMut(&mut Id)) {
+    d.view_options.visit_references(&mut visit);
+    match &mut d.projection {
+        ProjectionKind::StateMachine { machine } => visit(machine),
+        ProjectionKind::Scenario { scenario } => visit(scenario),
+        _ => {}
+    }
+    if let Some(layout) = &mut d.layout {
+        layout.visit_references(&mut visit);
+    }
+    for route in &mut d.routes {
+        visit(&mut route.edge);
+    }
+    for node in d.nodes.values_mut() {
+        for anchor in &mut node.port_anchors {
+            visit(&mut anchor.port);
+        }
+        visit(&mut node.element);
+    }
+}
+
+/// Preflight reference-key collisions before the caller changes object identities.
+/// Fresh targets are allowed. This is not whole-project admission: unrelated
+/// invalid records remain repairable within a transaction. Future typed reference
+/// domains must compose their own preflight here before any remap mutation.
+pub fn check_remap(p: &Project, old: Id, new: Id) -> Result<(), ModelError> {
+    if old == new {
+        return Ok(());
+    }
+    let remap = |id: Id| if id == old { new } else { id };
+    for diagram in p.diagrams.values() {
+        let Some(DiagramLayout::Scenario(layout)) = &diagram.layout else {
+            continue;
+        };
+        let mut lanes = std::collections::BTreeMap::new();
+        for lane in &layout.lanes {
+            let affected = lane.lifeline == old;
+            if let Some(previous_affected) = lanes.insert(remap(lane.lifeline), affected)
+                && (affected || previous_affected)
+            {
+                return Err(ModelError(
+                    "Identity remap would collide with a Scenario lane position.".into(),
+                ));
+            }
+        }
+        let mut messages = std::collections::BTreeMap::new();
+        for message in &layout.messages {
+            let mut address = message.address.clone();
+            let affected = address.occurrence == old || address.references.contains(&old);
+            address.occurrence = remap(address.occurrence);
+            for reference in &mut address.references {
+                *reference = remap(*reference);
+            }
+            if let Some(previous_affected) = messages.insert(address, affected)
+                && (affected || previous_affected)
+            {
+                return Err(ModelError(
+                    "Identity remap would collide with a Scenario message position.".into(),
+                ));
+            }
+        }
+    }
+    Ok(())
+}
+
+pub fn remap_references(p: &mut Project, old: Id, new: Id) -> Result<(), ModelError> {
+    check_remap(p, old, new)?;
     for e in p.elements.values_mut() {
         visit_element_refs(e, |id| {
             if *id == old {
@@ -219,31 +293,11 @@ pub fn remap_references(p: &mut Project, old: Id, new: Id) {
         });
     }
     for d in p.diagrams.values_mut() {
-        d.view_options.visit_references(|id| {
+        visit_diagram_refs(d, |id| {
             if *id == old {
                 *id = new;
             }
         });
-        if let ProjectionKind::StateMachine { machine } = &mut d.projection
-            && *machine == old
-        {
-            *machine = new;
-        }
-        for route in &mut d.routes {
-            if route.edge == old {
-                route.edge = new;
-            }
-        }
-        for n in d.nodes.values_mut() {
-            for anchor in &mut n.port_anchors {
-                if anchor.port == old {
-                    anchor.port = new;
-                }
-            }
-            if n.element == old {
-                n.element = new;
-            }
-        }
     }
     for a in p.artifact_links.values_mut() {
         if a.owner == old {
@@ -265,6 +319,7 @@ pub fn remap_references(p: &mut Project, old: Id, new: Id) {
             });
         }
     }
+    Ok(())
 }
 /// IDs removed by a cascade. Cross-layer traced counterparts are never included.
 pub fn deletion_impact(p: &Project, id: Id) -> BTreeSet<Id> {
@@ -339,7 +394,8 @@ fn deletion_impact_inner(p: &Project, id: Id, defer_exchange_allocations: bool)
         for d in p.diagrams.values() {
             if d.projection
                 .state_machine()
-                .is_some_and(|machine| removed.contains(&machine))
+                .or_else(|| d.projection.scenario())
+                .is_some_and(|owner| removed.contains(&owner))
             {
                 removed.insert(d.id);
             }
@@ -412,6 +468,7 @@ fn remove_objects(p: &mut Project, removed: BTreeSet<Id>) {
     p.artifact_links.retain(|id, _| !removed.contains(id));
     for d in p.diagrams.values_mut() {
         d.view_options.retain_references(|id| !removed.contains(id));
+        crate::scenario_layout::prune_deleted(d, &removed);
         d.nodes.retain(|id, _| !removed.contains(id));
         d.routes.retain(|route| !removed.contains(&route.edge));
         for node in d.nodes.values_mut() {
@@ -589,3 +646,7 @@ fn remove_objects(p: &mut Project, removed: BTreeSet<Id>) {
         }
     }
 }
+
+#[cfg(test)]
+#[path = "references/scenario_layout_tests.rs"]
+mod scenario_layout_tests;

crates/oa-core/src/references/scenario_layout_tests.rs

@@ -0,0 +1,388 @@
+use super::*;
+use std::collections::BTreeMap;
+
+struct Fixture {
+    project: Project,
+    owner: Id,
+    lanes: [Id; 2],
+    messages: [Id; 2],
+    views: [Id; 2],
+}
+
+fn address(occurrence: Id) -> OccurrenceEndpoint {
+    OccurrenceEndpoint {
+        references: vec![],
+        occurrence,
+    }
+}
+
+fn layout(project: &Project, view: Id) -> &ScenarioLayout {
+    let Some(DiagramLayout::Scenario(layout)) = &project.diagrams[&view].layout else {
+        panic!("expected authored Scenario positions")
+    };
+    layout
+}
+
+fn layout_mut(project: &mut Project, view: Id) -> &mut ScenarioLayout {
+    let Some(DiagramLayout::Scenario(layout)) =
+        &mut project.diagrams.get_mut(&view).unwrap().layout
+    else {
+        panic!("expected authored Scenario positions")
+    };
+    layout
+}
+
+fn admitted(project: &Project) {
+    let errors: Vec<_> = crate::validation::validate(project)
+        .into_iter()
+        .filter(|issue| issue.severity == crate::validation::Severity::Error)
+        .collect();
+    assert!(errors.is_empty(), "{errors:?}");
+}
+
+fn fixture() -> Fixture {
+    let mut project = Project::empty();
+    let owner = project
+        .add_element(Kind::Scenario, Layer::Oa, "Delivery", None)
+        .unwrap();
+    let lanes = ["Sender", "Receiver"].map(|name| {
+        project
+            .add_element(Kind::Lifeline, Layer::Oa, name, Some(owner))
+            .unwrap()
+    });
+    let messages = ["First message", "Second message"].map(|name| {
+        let id = project
+            .add_element(Kind::Occurrence, Layer::Oa, name, Some(owner))
+            .unwrap();
+        *project.elements.get_mut(&id).unwrap().shared_mut().unwrap() = SharedBody::Occurrence {
+            body: OccurrenceBody::Exchange {
+                exchange: None,
+                sender: Some(lanes[0]),
+                receiver: Some(lanes[1]),
+                message_kind: MessageKind::Asynchronous,
+                reply_to: None,
+                values: vec![],
+                operation: None,
+            },
+            precondition: String::new(),
+            postcondition: String::new(),
+        };
+        id
+    });
+    *project
+        .elements
+        .get_mut(&owner)
+        .unwrap()
+        .steps_mut()
+        .unwrap() = messages.to_vec();
+    let views = ["delivery_view", "review_view"].map(|alias| {
+        let id = Id::new_v4();
+        project.diagrams.insert(
+            id,
+            Diagram {
+                id,
+                alias: alias.into(),
+                name: alias.into(),
+                description: String::new(),
+                layer: Layer::Oa,
+                projection: ProjectionKind::Scenario { scenario: owner },
+                view_options: Default::default(),
+                nodes: BTreeMap::new(),
+                routes: vec![],
+                layout: Some(DiagramLayout::Scenario(ScenarioLayout {
+                    lanes: vec![
+                        ScenarioLanePosition {
+                            lifeline: lanes[0],
+                            x: 120.,
+                        },
+                        ScenarioLanePosition {
+                            lifeline: lanes[1],
+                            x: 420.,
+                        },
+                    ],
+                    messages: vec![
+                        ScenarioMessagePosition {
+                            address: address(messages[0]),
+                            send_y: 220.,
+                        },
+                        ScenarioMessagePosition {
+                            address: address(messages[1]),
+                            send_y: 360.,
+                        },
+                    ],
+                })),
+            },
+        );
+        id
+    });
+    admitted(&project);
+    Fixture {
+        project,
+        owner,
+        lanes,
+        messages,
+        views,
+    }
+}
+
+#[test]
+fn fresh_identity_swap_preserves_coordinates_and_semantic_sequence() {
+    let mut f = fixture();
+    let before = f.project.clone();
+    let temporary = Id::new_v4();
+    for ids in [f.lanes, f.messages] {
+        f.project = crate::execute_batch(
+            &f.project,
+            &[
+                Command::Reidentify(ids[0], temporary),
+                Command::Reidentify(ids[1], ids[0]),
+                Command::Reidentify(temporary, ids[1]),
+            ],
+        )
+        .unwrap();
+    }
+    admitted(&f.project);
+    assert_eq!(
+        f.project.elements[&f.owner].steps().unwrap(),
+        &vec![f.messages[1], f.messages[0]]
+    );
+    for view in f.views {
+        let rows = layout(&f.project, view);
+        assert_eq!(
+            rows.lanes,
+            vec![
+                ScenarioLanePosition {
+                    lifeline: f.lanes[1],
+                    x: 120.
+                },
+                ScenarioLanePosition {
+                    lifeline: f.lanes[0],
+                    x: 420.
+                }
+            ]
+        );
+        assert_eq!(
+            rows.messages,
+            vec![
+                ScenarioMessagePosition {
+                    address: address(f.messages[1]),
+                    send_y: 220.
+                },
+                ScenarioMessagePosition {
+                    address: address(f.messages[0]),
+                    send_y: 360.
+                }
+            ]
+        );
+    }
+    // Reverse the swaps: no values or identities other than those requested drift.
+    for ids in [f.lanes, f.messages] {
+        f.project = crate::execute_batch(
+            &f.project,
+            &[
+                Command::Reidentify(ids[0], temporary),
+                Command::Reidentify(ids[1], ids[0]),
+                Command::Reidentify(temporary, ids[1]),
+            ],
+        )
+        .unwrap();
+    }
+    assert_eq!(f.project, before);
+}
+
+#[test]
+fn colliding_lane_or_message_remap_rejects_before_any_reference_changes() {
+    for message in [false, true] {
+        let mut f = fixture();
+        let [old, new] = if message { f.messages } else { f.lanes };
+        let before = f.project.clone();
+        assert!(check_remap(&f.project, old, new).is_err());
+        assert!(remap_references(&mut f.project, old, new).is_err());
+        assert_eq!(f.project, before);
+    }
+}
+
+#[test]
+fn reidentify_preflight_precedes_object_map_mutation_for_fresh_colliding_target() {
+    let mut f = fixture();
+    let fresh = Id::new_v4();
+    // A repair candidate can already have a dangling coordinate key. It must not
+    // silently merge with the live lane, even though the destination ID is vacant.
+    layout_mut(&mut f.project, f.views[0]).lanes[1].lifeline = fresh;
+    let before = f.project.clone();
+    assert!(crate::session::reidentify(&mut f.project, f.lanes[0], fresh).is_err());
+    assert_eq!(f.project, before);
+}
+
+#[test]
+fn full_address_paths_are_walked_and_collision_checked_without_admitting_expansion() {
+    let mut f = fixture();
+    let [old, new] = [Id::new_v4(), Id::new_v4()];
+    let rows = layout_mut(&mut f.project, f.views[0]);
+    // Future/invalid expanded candidates still participate in reference safety.
+    rows.messages[0].address.references = vec![old];
+    rows.messages[1].address = OccurrenceEndpoint {
+        references: vec![new],
+        occurrence: f.messages[0],
+    };
+    let refs = diagram_references(&f.project.diagrams[&f.views[0]]);
+    assert!(refs.contains(&f.owner) && refs.contains(&old) && refs.contains(&new));
+    let before = f.project.clone();
+    assert!(remap_references(&mut f.project, old, new).is_err());
+    assert_eq!(f.project, before);
+    let fresh = Id::new_v4();
+    remap_references(&mut f.project, old, fresh).unwrap();
+    let rows = layout(&f.project, f.views[0]);
+    assert_eq!(rows.messages[0].address.references, vec![fresh]);
+    assert_eq!(rows.messages[0].address.occurrence, f.messages[0]);
+    assert_eq!(rows.messages[1].address.references, vec![new]);
+}
+
+#[test]
+fn owner_reidentify_and_delete_cover_all_saved_views_without_deleting_other_owners() {
+    let mut f = fixture();
+    let other_owner = f
+        .project
+        .add_element(Kind::Scenario, Layer::Oa, "Independent", None)
+        .unwrap();
+    let mut other_view = f.project.diagrams[&f.views[0]].clone();
+    other_view.id = Id::new_v4();
+    other_view.alias = "independent_view".into();
+    other_view.projection = ProjectionKind::Scenario {
+        scenario: other_owner,
+    };
+    other_view.layout = None;
+    f.project.diagrams.insert(other_view.id, other_view.clone());
+    admitted(&f.project);
+    let fresh_owner = Id::new_v4();
+    f.project = crate::prepare_command(&f.project, &Command::Reidentify(f.owner, fresh_owner))
+        .unwrap()
+        .project;
+    for view in f.views {
+        assert_eq!(
+            f.project.diagrams[&view].projection.scenario(),
+            Some(fresh_owner)
+        );
+    }
+    let impact = deletion_impact(&f.project, fresh_owner);
+    assert!(
+        f.views
+            .iter()
+            .chain(&f.lanes)
+            .chain(&f.messages)
+            .all(|id| impact.contains(id))
+    );
+    assert!(!impact.contains(&other_owner) && !impact.contains(&other_view.id));
+    delete_cascade(&mut f.project, fresh_owner);
+    assert_eq!(f.project.diagrams[&other_view.id], other_view);
+    assert!(
+        f.views
+            .iter()
+            .all(|id| !f.project.diagrams.contains_key(id))
+    );
+    admitted(&f.project);
+}
+
+#[test]
+fn deletion_then_recreation_never_resurrects_lane_or_message_coordinates() {
+    let mut f = fixture();
+    let lane = f.project.elements[&f.lanes[0]].clone();
+    let message = f.project.elements[&f.messages[0]].clone();
+    delete_cascade(&mut f.project, lane.id);
+    for view in f.views {
+        let rows = layout(&f.project, view);
+        assert_eq!(rows.lanes.len(), 1);
+        assert_eq!(rows.lanes[0].lifeline, f.lanes[1]);
+        // Missing endpoint assignment does not erase a still-live message's spacing.
+        assert_eq!(rows.messages.len(), 2);
+    }
+    let mut pending = BTreeSet::new();
+    delete_cascade_deferred(&mut f.project, message.id, &mut pending);
+    // Pruning happens during deletion, before later batch commands can recreate IDs.
+    assert!(
+        layout(&f.project, f.views[0])
+            .messages
+            .iter()
+            .all(|row| row.address.occurrence != message.id)
+    );
+    f.project.elements.insert(lane.id, lane);
+    f.project.elements.insert(message.id, message);
+    f.project
+        .elements
+        .get_mut(&f.owner)
+        .unwrap()
+        .steps_mut()
+        .unwrap()
+        .insert(0, f.messages[0]);
+    finish_deletions(&mut f.project, &pending);
+    for view in f.views {
+        let rows = layout(&f.project, view);
+        assert_eq!(rows.lanes.len(), 1);
+        assert_eq!(
+            rows.messages,
+            vec![ScenarioMessagePosition {
+                address: address(f.messages[1]),
+                send_y: 360.
+            }]
+        );
+    }
+    admitted(&f.project);
+}
+
+#[test]
+fn unrelated_invalid_records_do_not_block_scoped_remap_or_get_repaired_implicitly() {
+    let mut f = fixture();
+    let unrelated = Id::new_v4();
+    let rows = layout_mut(&mut f.project, f.views[1]);
+    let invalid = ScenarioLanePosition {
+        lifeline: unrelated,
+        x: MAX_COORDINATE * 2.,
+    };
+    rows.lanes.extend([invalid.clone(), invalid]);
+    let fresh = Id::new_v4();
+    let untouched = f.project.diagrams[&f.views[1]].clone();
+    let before = f.project.clone();
+    remap_references(&mut f.project, f.owner, f.owner).unwrap();
+    assert_eq!(f.project, before);
+    // The duplicate lane records do not involve the remapped message identity.
+    remap_references(&mut f.project, f.messages[0], fresh).unwrap();
+    assert_eq!(
+        layout(&f.project, f.views[1]).lanes,
+        layout_from(&untouched).lanes
+    );
+    assert_eq!(
+        layout(&f.project, f.views[1]).messages[0]
+            .address
+            .occurrence,
+        fresh
+    );
+    assert_eq!(layout(&f.project, f.views[1]).messages[0].send_y, 220.);
+}
+
+fn layout_from(diagram: &Diagram) -> &ScenarioLayout {
+    let Some(DiagramLayout::Scenario(layout)) = &diagram.layout else {
+        panic!("missing layout")
+    };
+    layout
+}
+
+#[test]
+fn deletion_prunes_an_explicit_address_path_without_pruning_other_message_rows() {
+    let mut f = fixture();
+    // Expanded addresses are not admitted in this slice, but deleting their
+    // explicit references must still make an intermediate repair candidate safe.
+    layout_mut(&mut f.project, f.views[0]).messages[0]
+        .address
+        .references = vec![f.lanes[0]];
+    delete_cascade(&mut f.project, f.lanes[0]);
+    assert_eq!(
+        layout(&f.project, f.views[0]).messages,
+        vec![ScenarioMessagePosition {
+            address: address(f.messages[1]),
+            send_y: 360.
+        }]
+    );
+    assert_eq!(layout(&f.project, f.views[1]).messages.len(), 2);
+    assert!(f.project.elements.contains_key(&f.messages[0]));
+    admitted(&f.project);
+}

crates/oa-core/src/routing.rs

@@ -1,7 +1,12 @@
 //! Deterministic, bounded diagram geometry. Only authored pins belong in the model;
 //! callers share this derived geometry for drawing, picking, fitting and export.
 use crate::projection::{self, ProjectedEdge, ProjectedNode, ProjectedView};
-use crate::{Diagram, Id, Position, Project, Relation, RelationBody, RelationKind, Size};
+use crate::{
+    Diagram, EdgeAttachment, EdgeEnd, Id, PortAnchorSide, Position, Project, Relation,
+    RelationBody, RelationKind, Size,
+};
+mod attachments;
+pub use attachments::{attachment_from_point, attachment_point, semantic_port_endpoint};
 use std::cmp::Ordering;
 use std::collections::{BTreeMap, BTreeSet, BinaryHeap};
 use std::fmt;
@@ -41,6 +46,7 @@ pub struct RoutedEdge {
     // Derived solver state, never persisted. A preview must inherit the same
     // remaining work budget as this edge had in stable-ID settled traversal.
     search_budget_before: usize,
+    attachments: [Option<EdgeAttachment>; 2],
 }
 
 #[derive(Debug, Clone, PartialEq)]
@@ -173,6 +179,7 @@ pub fn association_end_geometry(
 
 #[derive(Debug, Clone, PartialEq, Eq)]
 pub enum RouteWarning {
+    CoincidentAttachments,
     PinInsideObstacle { pin: usize, obstacle: Id },
     NoClearPath,
     SearchBudgetExhausted,
@@ -181,6 +188,9 @@ pub enum RouteWarning {
 impl fmt::Display for RouteWarning {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         match self {
+            Self::CoincidentAttachments => f.write_str(
+                "The two attachments coincide; move either end to separate the loop tips.",
+            ),
             Self::PinInsideObstacle { pin, .. } => {
                 write!(f, "Bend {} is inside a card or its clearance", pin + 1)
             }
@@ -374,7 +384,14 @@ struct Endpoint {
     point: Position,
     stub: Position,
 }
-fn endpoints(node: &ProjectedNode, port: Option<Id>, view: &ProjectedView) -> Vec<Endpoint> {
+fn endpoints(
+    project: &Project,
+    diagram: &Diagram,
+    node: &ProjectedNode,
+    port: Option<Id>,
+    view: &ProjectedView,
+    attachment: Option<EdgeAttachment>,
+) -> Vec<Endpoint> {
     if let Some(port) = port.and_then(|id| {
         view.ports
             .iter()
@@ -389,26 +406,18 @@ fn endpoints(node: &ProjectedNode, port: Option<Id>, view: &ProjectedView) -> Ve
             ),
         }];
     }
-    let r = Rect::node(node);
-    let mid = pos((r.left + r.right) / 2.0, (r.top + r.bottom) / 2.0);
-    vec![
-        Endpoint {
-            point: pos(r.left, mid.y),
-            stub: pos(r.left - PORT_STUB, mid.y),
-        },
-        Endpoint {
-            point: pos(r.right, mid.y),
-            stub: pos(r.right + PORT_STUB, mid.y),
-        },
-        Endpoint {
-            point: pos(mid.x, r.top),
-            stub: pos(mid.x, r.top - PORT_STUB),
-        },
-        Endpoint {
-            point: pos(mid.x, r.bottom),
-            stub: pos(mid.x, r.bottom + PORT_STUB),
-        },
+    if let Some(attachment) = attachment {
+        return vec![attachments::endpoint(project, diagram, node, attachment)];
+    }
+    [
+        PortAnchorSide::Left,
+        PortAnchorSide::Right,
+        PortAnchorSide::Top,
+        PortAnchorSide::Bottom,
     ]
+    .into_iter()
+    .map(|side| attachments::endpoint(project, diagram, node, EdgeAttachment { side, offset: 0.5 }))
+    .collect()
 }
 
 fn ancestors(id: Id, nodes: &BTreeMap<Id, &ProjectedNode>, out: &mut BTreeSet<Id>) {
@@ -507,6 +516,12 @@ fn route_diagram_impl(
             .is_some_and(|(source, target)| source != edge.source || target != edge.target);
         let custom_suspended = promoted;
         let route = if promoted { None } else { stored };
+        let attachments = [EdgeEnd::Source, EdgeEnd::Target].map(|end| {
+            semantic_port_endpoint(project, edge.id, end)
+                .is_none()
+                .then(|| route.and_then(|r| r.attachment(end)))
+                .flatten()
+        });
         let pins = route.map_or_else(Vec::new, |r| r.waypoints.clone());
         let obstacles = edge_obstacles(edge, &nodes, &rectangles, &headers);
 
@@ -517,7 +532,10 @@ fn route_diagram_impl(
         });
         if let Some(cached) = cached {
             budget = cached.search_budget_before;
-            if cached.pins == pins && cached.custom_suspended == custom_suspended {
+            if cached.pins == pins
+                && cached.attachments == attachments
+                && cached.custom_suspended == custom_suspended
+            {
                 // Label-only editing cannot change the connection beneath the
                 // pointer, including a settled fallback with routing warnings.
                 for &point in &cached.points {
@@ -543,9 +561,22 @@ fn route_diagram_impl(
         }
         let (points, pin_lengths, failure) = route_edge(
             edge,
-            source,
-            target,
-            view,
+            &endpoints(
+                project,
+                diagram,
+                source,
+                semantic_port_endpoint(project, edge.id, EdgeEnd::Source).or(edge.source_port),
+                view,
+                attachments[0],
+            ),
+            &endpoints(
+                project,
+                diagram,
+                target,
+                semantic_port_endpoint(project, edge.id, EdgeEnd::Target).or(edge.target_port),
+                view,
+                attachments[1],
+            ),
             &pins,
             &obstacles,
             &previous,
@@ -574,6 +605,7 @@ fn route_diagram_impl(
                 warnings,
                 custom_suspended,
                 search_budget_before,
+                attachments,
             },
         );
     }
@@ -679,6 +711,46 @@ struct RoutingSpace<'a> {
     xs: Vec<f32>,
     ys: Vec<f32>,
 }
+
+fn coincident_detour(a: Endpoint, obstacles: &[Rect]) -> [Position; 3] {
+    let direction = |delta: f32| if delta == 0. { 0. } else { delta.signum() };
+    let normal = pos(
+        direction(a.stub.x - a.point.x),
+        direction(a.stub.y - a.point.y),
+    );
+    let tangent = pos(-normal.y, normal.x);
+    let candidates: Vec<_> = [36., 72., 144., 288.]
+        .into_iter()
+        .flat_map(|extent| {
+            [-1., 1.].into_iter().map(move |side| {
+                [
+                    pos(a.stub.x + normal.x * extent, a.stub.y + normal.y * extent),
+                    pos(
+                        a.stub.x + (normal.x + tangent.x * side) * extent,
+                        a.stub.y + (normal.y + tangent.y * side) * extent,
+                    ),
+                    pos(
+                        a.stub.x + tangent.x * side * extent,
+                        a.stub.y + tangent.y * side * extent,
+                    ),
+                ]
+            })
+        })
+        .collect();
+    // These are computed loop guards, not authored hard pins. Prefer a clear
+    // orientation/size before asking the bounded router to connect them.
+    candidates
+        .iter()
+        .find(|p| clear_path(&[a.stub, p[0], p[1], p[2], a.stub], obstacles))
+        .or_else(|| {
+            candidates.iter().find(|p| {
+                p.iter()
+                    .all(|point| !obstacles.iter().any(|r| r.contains(*point)))
+            })
+        })
+        .copied()
+        .unwrap_or(candidates[0])
+}
 impl<'a> RoutingSpace<'a> {
     fn new(obstacles: &'a [Rect]) -> Self {
         Self {
@@ -692,24 +764,41 @@ impl<'a> RoutingSpace<'a> {
 #[allow(clippy::too_many_arguments)]
 fn route_edge(
     edge: &ProjectedEdge,
-    source: &ProjectedNode,
-    target: &ProjectedNode,
-    view: &ProjectedView,
+    source_ends: &[Endpoint],
+    target_ends: &[Endpoint],
     pins: &[Position],
     obstacles: &[Rect],
     previous: &[Segment],
     budget: &mut usize,
 ) -> EdgePath {
+    // Coincident authored tips are valid presentation, including on self loops.
+    // Preserve them and add an external detour; never index an empty candidate
+    // list or turn the connection into an out-and-back degenerate stub.
+    let coincident = edge.source == edge.target
+        && source_ends.len() == 1
+        && target_ends.len() == 1
+        && source_ends[0].point == target_ends[0].point
+        && source_ends[0].stub == target_ends[0].stub;
+    let authored_pin_count = pins.len();
+    let mut loop_pins = Vec::new();
+    if coincident {
+        let a = source_ends[0];
+        loop_pins.extend_from_slice(pins);
+        loop_pins.extend(coincident_detour(a, obstacles));
+    }
+    let pins = if coincident { &loop_pins[..] } else { pins };
     let space = RoutingSpace::new(obstacles);
     let mut candidates = Vec::new();
-    for a in endpoints(source, edge.source_port, view) {
-        for b in endpoints(target, edge.target_port, view) {
+    for &a in source_ends {
+        for &b in target_ends {
             // A real self-relation must leave and return at distinct anchors.
             // Reusing one anchor makes the cheapest path a degenerate stub.
             if edge.source == edge.target
                 && edge.source_port.is_none()
                 && edge.target_port.is_none()
                 && a.point == b.point
+                && a.stub == b.stub
+                && !coincident
             {
                 continue;
             }
@@ -729,10 +818,9 @@ fn route_edge(
     // Try all side combinations cheaply before spending the bounded grid budget.
     for search in [false, true] {
         for &(estimate, a, b) in &candidates {
-            if best
-                .as_ref()
-                .is_some_and(|(cost, _, _)| estimate + 2.0 * PORT_STUB > *cost)
-            {
+            if best.as_ref().is_some_and(|(cost, _, _)| {
+                estimate + manhattan(a.point, a.stub) + manhattan(b.point, b.stub) > *cost
+            }) {
                 continue;
             }
             if obstacles
@@ -748,7 +836,7 @@ fn route_edge(
             let mut occupied = previous.to_vec();
             record_segments(&mut occupied, &points);
             let mut pin_lengths = Vec::new();
-            let mut distance = PORT_STUB;
+            let mut distance = manhattan(a.point, a.stub);
             let mut start = a.stub;
             let mut failed = false;
             for (index, end) in pins
@@ -792,15 +880,20 @@ fn route_edge(
             break;
         }
     }
-    if let Some((_, points, pin_lengths)) = best {
-        return (points, pin_lengths, None);
+    if let Some((_, points, mut pin_lengths)) = best {
+        pin_lengths.truncate(authored_pin_count);
+        return (
+            points,
+            pin_lengths,
+            coincident.then_some(RouteWarning::CoincidentAttachments),
+        );
     }
     // Recoverable fallback retains every hard pin, in order, and the actual port
     // leads. Its warning is deliberately visible to consumers.
     let (_, a, b) = candidates[0];
     let mut points = vec![a.point, a.stub];
     let mut pin_lengths = Vec::new();
-    let mut distance = PORT_STUB;
+    let mut distance = manhattan(a.point, a.stub);
     let mut start = a.stub;
     for (index, end) in pins
         .iter()
@@ -833,6 +926,7 @@ fn route_edge(
         start = end;
     }
     points.push(b.point);
+    pin_lengths.truncate(authored_pin_count);
     (
         points,
         pin_lengths,

crates/oa-core/src/routing/attachments.rs

@@ -0,0 +1,160 @@
+//! One boundary definition shared by persisted routing and attachment gestures.
+use super::*;
+use crate::{EdgeAttachment, EdgeEnd, Kind, PortAnchorSide};
+
+/// Semantic authority, independent of whether projection currently exposes a port.
+pub fn semantic_port_endpoint(project: &Project, edge: Id, end: EdgeEnd) -> Option<Id> {
+    let endpoint = if let Some(relation) = project.relations.get(&edge) {
+        match (&relation.body, end) {
+            (RelationBody::FunctionalExchange { source_port, .. }, EdgeEnd::Source) => *source_port,
+            (RelationBody::FunctionalExchange { target_port, .. }, EdgeEnd::Target) => *target_port,
+            (_, EdgeEnd::Source) => relation.source(),
+            (_, EdgeEnd::Target) => relation.target(),
+        }
+    } else {
+        let trace = project.traces.get(&edge)?;
+        match end {
+            EdgeEnd::Source => trace.oa,
+            EdgeEnd::Target => trace.sa,
+        }
+    };
+    project
+        .elements
+        .get(&endpoint)
+        .filter(|e| e.kind() == Kind::Port)
+        .map(|_| endpoint)
+}
+
+/// Intersect the chosen cardinal scan line with the painted shape. Offset is
+/// measured over the complete projected bounding side, including its corners.
+/// Terminate's X uses its outermost stroke intersection rather than a contour.
+pub fn attachment_point(
+    project: &Project,
+    diagram: &Diagram,
+    node: &ProjectedNode,
+    attachment: &EdgeAttachment,
+) -> Position {
+    let vertical = matches!(
+        attachment.side,
+        PortAnchorSide::Left | PortAnchorSide::Right
+    );
+    let (extent, depth) = if vertical {
+        (node.size.height, node.size.width)
+    } else {
+        (node.size.width, node.size.height)
+    };
+    let along = attachment.offset.clamp(0., 1.) * extent;
+    let t = 2. * attachment.offset.clamp(0., 1.) - 1.;
+    let kind = diagram
+        .projection
+        .state_machine()
+        .and_then(|_| project.elements.get(&node.element))
+        .map(|e| e.kind());
+    let inset = match kind {
+        Some(Kind::Choice) => depth * 0.5 * t.abs(),
+        Some(Kind::Terminate) => {
+            depth
+                * attachment
+                    .offset
+                    .clamp(0., 1.)
+                    .min(1. - attachment.offset.clamp(0., 1.))
+        }
+        Some(
+            Kind::Initial
+            | Kind::Junction
+            | Kind::Final
+            | Kind::ShallowHistory
+            | Kind::DeepHistory
+            | Kind::EntryPoint
+            | Kind::ExitPoint,
+        ) => depth * 0.5 * (1. - (1. - t * t).max(0.).sqrt()),
+        Some(Kind::Region | Kind::Fork | Kind::Join) => 0.,
+        _ => {
+            let radius = 10_f32.min(extent / 2.).min(depth / 2.);
+            let corner = (radius - along.min(extent - along)).max(0.);
+            radius - (radius * radius - corner * corner).max(0.).sqrt()
+        }
+    };
+    match attachment.side {
+        PortAnchorSide::Left => pos(node.position.x + inset, node.position.y + along),
+        PortAnchorSide::Right => pos(
+            node.position.x + node.size.width - inset,
+            node.position.y + along,
+        ),
+        PortAnchorSide::Top => pos(node.position.x + along, node.position.y + inset),
+        PortAnchorSide::Bottom => pos(
+            node.position.x + along,
+            node.position.y + node.size.height - inset,
+        ),
+    }
+}
+
+/// Choose a cardinal bounding side, then map its fraction onto the painted
+/// contour. Contour distances cannot distinguish the sides of a circle at its
+/// extrema: Right/0 and Top/0.5 denote the same point but different lead directions.
+/// Hysteresis is in diagram units, capped for small symbols. Only UI snapping
+/// rounds to hundredths: source/API values retain their complete precision.
+pub fn attachment_from_point(
+    node: &ProjectedNode,
+    cursor: Position,
+    previous: Option<PortAnchorSide>,
+    hysteresis: f32,
+) -> EdgeAttachment {
+    let candidate = |side| EdgeAttachment {
+        side,
+        offset: projection::port_anchor_offset(node, side, cursor),
+    };
+    // Measure side intent at the box, not from a distant overshoot: Euclidean
+    // distance differences converge outside a small symbol and would otherwise
+    // let hysteresis retain a perpendicular side indefinitely.
+    let boundary_cursor = pos(
+        cursor
+            .x
+            .clamp(node.position.x, node.position.x + node.size.width),
+        cursor
+            .y
+            .clamp(node.position.y, node.position.y + node.size.height),
+    );
+    let distance = |side| {
+        length(
+            projection::port_anchor_position(node, side, candidate(side).offset),
+            boundary_cursor,
+        )
+    };
+    let mut side = [
+        PortAnchorSide::Left,
+        PortAnchorSide::Right,
+        PortAnchorSide::Top,
+        PortAnchorSide::Bottom,
+    ]
+    .into_iter()
+    .min_by(|a, b| distance(*a).total_cmp(&distance(*b)))
+    .unwrap();
+    let hysteresis = hysteresis
+        .max(0.)
+        .min(node.size.width.min(node.size.height) * 0.2);
+    if let Some(old) = previous
+        && distance(old) <= distance(side) + hysteresis
+    {
+        side = old;
+    }
+    let mut attachment = candidate(side);
+    attachment.offset = (attachment.offset * 100.).round() / 100.;
+    attachment
+}
+
+pub(super) fn endpoint(
+    project: &Project,
+    diagram: &Diagram,
+    node: &ProjectedNode,
+    attachment: EdgeAttachment,
+) -> Endpoint {
+    let point = attachment_point(project, diagram, node, &attachment);
+    let stub = match attachment.side {
+        PortAnchorSide::Left => pos(node.position.x - PORT_STUB, point.y),
+        PortAnchorSide::Right => pos(node.position.x + node.size.width + PORT_STUB, point.y),
+        PortAnchorSide::Top => pos(point.x, node.position.y - PORT_STUB),
+        PortAnchorSide::Bottom => pos(point.x, node.position.y + node.size.height + PORT_STUB),
+    };
+    Endpoint { point, stub }
+}

crates/oa-core/src/scenario_layout.rs

@@ -0,0 +1,429 @@
+//! Authored Scenario presentation. Structural admission never changes event order.
+use crate::{
+    Diagram, Id, Kind, Layer, MAX_COORDINATE, ModelError, OccurrenceBody, OccurrenceEndpoint,
+    Project, SharedBody, validation,
+};
+use serde::{Deserialize, Serialize};
+use std::collections::BTreeSet;
+
+#[derive(Debug, Clone, PartialEq, Serialize, Deserialize)]
+#[serde(deny_unknown_fields)]
+pub enum DiagramLayout {
+    Scenario(ScenarioLayout),
+}
+
+#[derive(Debug, Clone, PartialEq, Serialize, Deserialize, Default)]
+#[serde(deny_unknown_fields)]
+pub struct ScenarioLayout {
+    #[serde(default)]
+    pub lanes: Vec<ScenarioLanePosition>,
+    #[serde(default)]
+    pub messages: Vec<ScenarioMessagePosition>,
+}
+
+#[derive(Debug, Clone, PartialEq, Serialize, Deserialize)]
+#[serde(deny_unknown_fields)]
+pub struct ScenarioLanePosition {
+    pub lifeline: Id,
+    pub x: f32,
+}
+
+#[derive(Debug, Clone, PartialEq, Serialize, Deserialize)]
+#[serde(deny_unknown_fields)]
+pub struct ScenarioMessagePosition {
+    pub address: OccurrenceEndpoint,
+    /// Actual send endpoint, not the renderer's receive-oriented lifecycle row.
+    pub send_y: f32,
+}
+
+impl DiagramLayout {
+    /// Visit every explicit reference, including unsupported paths in a candidate.
+    /// The caller owns remap preflight and final atomic validation.
+    pub fn visit_references(&mut self, mut visit: impl FnMut(&mut Id)) {
+        match self {
+            Self::Scenario(layout) => {
+                for lane in &mut layout.lanes {
+                    visit(&mut lane.lifeline);
+                }
+                for message in &mut layout.messages {
+                    for reference in &mut message.address.references {
+                        visit(reference);
+                    }
+                    visit(&mut message.address.occurrence);
+                }
+            }
+        }
+    }
+}
+
+/// Proposed aggregate accounting contribution; the shared admission owner applies it.
+/// One payload plus one record per lane/message. No graph objects are introduced.
+pub fn record_count(diagram: &Diagram) -> usize {
+    match &diagram.layout {
+        None => 0,
+        Some(DiagramLayout::Scenario(layout)) => 1usize
+            .saturating_add(layout.lanes.len())
+            .saturating_add(layout.messages.len()),
+    }
+}
+
+fn coordinate(value: f32) -> bool {
+    value.is_finite() && value.abs() <= MAX_COORDINATE
+}
+
+fn owner(p: &Project, diagram: &Diagram) -> Result<Id, ModelError> {
+    let scenario = diagram
+        .projection
+        .scenario()
+        .ok_or_else(|| ModelError("Scenario layout requires a Scenario projection.".into()))?;
+    if !p
+        .elements
+        .get(&scenario)
+        .is_some_and(|element| element.kind() == Kind::Scenario && element.layer() == diagram.layer)
+    {
+        return Err(ModelError(
+            "Scenario projection requires an existing Scenario in the diagram layer.".into(),
+        ));
+    }
+    Ok(scenario)
+}
+
+fn lane_member(p: &Project, owner: Id, layer: Layer, lifeline: Id) -> bool {
+    p.elements.get(&lifeline).is_some_and(|element| {
+        element.kind() == Kind::Lifeline
+            && element.parent == Some(owner)
+            && element.layer() == layer
+    })
+}
+
+/// Only actual steps of this Scenario and its own Fragment/Branch sequences.
+/// ScenarioUse/SequenceReference are deliberately never expanded. Invalid graph
+/// cycles terminate, and malformed parent/step links do not manufacture membership.
+fn direct_messages(p: &Project, owner: Id, layer: Layer) -> BTreeSet<Id> {
+    let mut messages = BTreeSet::new();
+    let mut visited = BTreeSet::new();
+    let mut pending = vec![owner];
+    while let Some(scope) = pending.pop() {
+        if !visited.insert(scope) {
+            continue;
+        }
+        let Some(element) = p.elements.get(&scope) else {
+            continue;
+        };
+        for id in element.steps().into_iter().flatten() {
+            let Some(item) = p.elements.get(id) else {
+                continue;
+            };
+            if item.parent != Some(scope) || item.layer() != layer {
+                continue;
+            }
+            match item.shared() {
+                Some(SharedBody::Occurrence {
+                    body: OccurrenceBody::Exchange { .. },
+                    ..
+                }) => {
+                    messages.insert(*id);
+                }
+                Some(SharedBody::Occurrence {
+                    body: OccurrenceBody::Fragment { branches, .. },
+                    ..
+                }) => {
+                    for branch in branches {
+                        if p.elements.get(branch).is_some_and(|operand| {
+                            operand.parent == Some(*id)
+                                && operand.layer() == layer
+                                && matches!(
+                                    operand.shared(),
+                                    Some(SharedBody::Occurrence {
+                                        body: OccurrenceBody::Branch { .. },
+                                        ..
+                                    })
+                                )
+                        }) {
+                            pending.push(*branch);
+                        }
+                    }
+                }
+                _ => {}
+            }
+        }
+    }
+    messages
+}
+
+pub(crate) fn validate_diagram(p: &Project, diagram: &Diagram, out: &mut Vec<validation::Issue>) {
+    if diagram.projection.scenario().is_none() {
+        if diagram.layout.is_some() {
+            validation::error(
+                out,
+                diagram.id,
+                "scenario_layout_projection",
+                "layout",
+                "Only a Scenario projection accepts a Scenario layout, including an empty payload.",
+            );
+        }
+        return;
+    }
+    let scenario = match owner(p, diagram) {
+        Ok(owner) => owner,
+        Err(error) => {
+            validation::error(
+                out,
+                diagram.id,
+                "scenario_diagram_context",
+                "projection",
+                error.0,
+            );
+            return;
+        }
+    };
+    if !diagram.nodes.is_empty() || !diagram.routes.is_empty() {
+        validation::error(
+            out,
+            diagram.id,
+            "scenario_diagram_content",
+            "layout",
+            "Scenario views do not accept architecture node placements or edge routes.",
+        );
+    }
+    let Some(DiagramLayout::Scenario(layout)) = &diagram.layout else {
+        return;
+    };
+    let mut lanes = BTreeSet::new();
+    for lane in &layout.lanes {
+        if !lanes.insert(lane.lifeline) {
+            validation::error(
+                out,
+                diagram.id,
+                "duplicate_scenario_lane",
+                "layout",
+                "A Scenario layout has at most one position per lifeline.",
+            );
+        }
+        if !lane_member(p, scenario, diagram.layer, lane.lifeline) {
+            validation::error(
+                out,
+                diagram.id,
+                "scenario_layout_lifeline",
+                "layout",
+                "Lane positions reference a Lifeline directly owned by the projected Scenario.",
+            );
+        }
+        if !coordinate(lane.x) {
+            validation::error(
+                out,
+                diagram.id,
+                "scenario_layout_coordinate",
+                "layout",
+                "Scenario positions must be finite and within the shared coordinate bounds.",
+            );
+        }
+    }
+    let members = direct_messages(p, scenario, diagram.layer);
+    let mut addresses = BTreeSet::new();
+    for message in &layout.messages {
+        // Reject expanded paths without cloning or indexing their potentially large contents.
+        if !message.address.references.is_empty() {
+            validation::error(
+                out,
+                diagram.id,
+                "scenario_layout_address",
+                "layout",
+                "Expanded-reference message positions are not supported; references must be empty.",
+            );
+        } else if !addresses.insert(message.address.occurrence) {
+            validation::error(
+                out,
+                diagram.id,
+                "duplicate_scenario_message",
+                "layout",
+                "A Scenario layout has at most one position per message address.",
+            );
+        }
+        if !members.contains(&message.address.occurrence) {
+            validation::error(
+                out,
+                diagram.id,
+                "scenario_layout_message",
+                "layout",
+                "Message positions reference Exchange occurrences in the Scenario's own ordered sequence tree.",
+            );
+        }
+        if !coordinate(message.send_y) {
+            validation::error(
+                out,
+                diagram.id,
+                "scenario_layout_coordinate",
+                "layout",
+                "Scenario positions must be finite and within the shared coordinate bounds.",
+            );
+        }
+    }
+}
+
+fn editable(p: &Project, id: Id) -> Result<(&Diagram, Id), ModelError> {
+    let diagram = p
+        .diagrams
+        .get(&id)
+        .ok_or_else(|| ModelError("Scenario diagram does not exist.".into()))?;
+    let scenario = owner(p, diagram)?;
+    if !diagram.nodes.is_empty() || !diagram.routes.is_empty() {
+        return Err(ModelError(
+            "Scenario views do not accept architecture node placements or edge routes.".into(),
+        ));
+    }
+    Ok((diagram, scenario))
+}
+
+fn check_message(
+    p: &Project,
+    diagram: &Diagram,
+    owner: Id,
+    address: &OccurrenceEndpoint,
+) -> Result<(), ModelError> {
+    if !address.references.is_empty() {
+        return Err(ModelError(
+            "Expanded-reference message positions are not supported; references must be empty."
+                .into(),
+        ));
+    }
+    if !direct_messages(p, owner, diagram.layer).contains(&address.occurrence) {
+        return Err(ModelError("Message position requires an Exchange occurrence in the Scenario's own ordered sequence tree.".into()));
+    }
+    Ok(())
+}
+
+fn payload(diagram: &mut Diagram) -> &mut ScenarioLayout {
+    let DiagramLayout::Scenario(layout) = diagram
+        .layout
+        .get_or_insert_with(|| DiagramLayout::Scenario(ScenarioLayout::default()));
+    layout
+}
+
+/// Target-scoped preparation, not whole-project or whole-layout validation.
+/// Unrelated intermediate errors remain repairable by later commands in a batch.
+pub fn set_lane(
+    p: &Project,
+    diagram: Id,
+    position: ScenarioLanePosition,
+) -> Result<Diagram, ModelError> {
+    let (current, owner) = editable(p, diagram)?;
+    if !lane_member(p, owner, current.layer, position.lifeline) || !coordinate(position.x) {
+        return Err(ModelError(
+            "Lane position requires an owned Lifeline and a finite bounded x coordinate.".into(),
+        ));
+    }
+    let mut result = current.clone();
+    let layout = payload(&mut result);
+    if layout
+        .lanes
+        .iter()
+        .filter(|row| row.lifeline == position.lifeline)
+        .count()
+        > 1
+    {
+        return Err(ModelError(
+            "Cannot set an ambiguous duplicate lane position.".into(),
+        ));
+    }
+    if let Some(existing) = layout
+        .lanes
+        .iter_mut()
+        .find(|row| row.lifeline == position.lifeline)
+    {
+        if existing.x != position.x {
+            *existing = position;
+        }
+    } else {
+        layout.lanes.push(position);
+    }
+    Ok(result)
+}
+
+pub fn remove_lane(p: &Project, diagram: Id, lifeline: Id) -> Result<Diagram, ModelError> {
+    let (current, owner) = editable(p, diagram)?;
+    if !lane_member(p, owner, current.layer, lifeline) {
+        return Err(ModelError(
+            "Removing a lane position requires an owned Lifeline.".into(),
+        ));
+    }
+    let mut result = current.clone();
+    if let Some(DiagramLayout::Scenario(layout)) = &mut result.layout {
+        layout.lanes.retain(|row| row.lifeline != lifeline);
+    }
+    Ok(result)
+}
+
+pub fn set_message(
+    p: &Project,
+    diagram: Id,
+    position: ScenarioMessagePosition,
+) -> Result<Diagram, ModelError> {
+    let (current, owner) = editable(p, diagram)?;
+    check_message(p, current, owner, &position.address)?;
+    if !coordinate(position.send_y) {
+        return Err(ModelError(
+            "Message position requires a finite bounded send_y coordinate.".into(),
+        ));
+    }
+    let mut result = current.clone();
+    let layout = payload(&mut result);
+    if layout
+        .messages
+        .iter()
+        .filter(|row| row.address == position.address)
+        .count()
+        > 1
+    {
+        return Err(ModelError(
+            "Cannot set an ambiguous duplicate message position.".into(),
+        ));
+    }
+    if let Some(existing) = layout
+        .messages
+        .iter_mut()
+        .find(|row| row.address == position.address)
+    {
+        if existing.send_y != position.send_y {
+            *existing = position;
+        }
+    } else {
+        layout.messages.push(position);
+    }
+    Ok(result)
+}
+
+pub fn remove_message(
+    p: &Project,
+    diagram: Id,
+    address: &OccurrenceEndpoint,
+) -> Result<Diagram, ModelError> {
+    let (current, owner) = editable(p, diagram)?;
+    check_message(p, current, owner, address)?;
+    let mut result = current.clone();
+    if let Some(DiagramLayout::Scenario(layout)) = &mut result.layout {
+        layout.messages.retain(|row| &row.address != address);
+    }
+    Ok(result)
+}
+
+/// Prune only identities in the caller's actual deletion closure, never visibility
+/// or missing endpoint assignments. Owner-view cascade remains the caller's job.
+pub fn prune_deleted(diagram: &mut Diagram, deleted: &BTreeSet<Id>) {
+    if let Some(DiagramLayout::Scenario(layout)) = &mut diagram.layout {
+        layout
+            .lanes
+            .retain(|lane| !deleted.contains(&lane.lifeline));
+        layout.messages.retain(|message| {
+            !deleted.contains(&message.address.occurrence)
+                && !message
+                    .address
+                    .references
+                    .iter()
+                    .any(|id| deleted.contains(id))
+        });
+    }
+}
+
+#[cfg(test)]
+mod tests;

crates/oa-core/src/scenario_layout/tests.rs

@@ -0,0 +1,802 @@
+use super::*;
+use crate::{
+    Element, FragmentOperator, MessageKind, ProjectionKind, Relation, RelationBody, RelationKind,
+    ScenarioViewpoint,
+};
+use std::collections::BTreeMap;
+
+struct Fixture {
+    project: Project,
+    owner: Id,
+    performer: Id,
+    lane: Id,
+    repeated_lane: Id,
+    first: Id,
+    second: Id,
+    nested: Id,
+    fragment: Id,
+    branch: Id,
+    view: Id,
+    other_view: Id,
+    exchange: Id,
+}
+
+fn set_body(element: &mut Element, body: OccurrenceBody) {
+    *element.shared_mut().unwrap() = SharedBody::Occurrence {
+        body,
+        precondition: String::new(),
+        postcondition: String::new(),
+    };
+}
+fn address(occurrence: Id) -> OccurrenceEndpoint {
+    OccurrenceEndpoint {
+        references: vec![],
+        occurrence,
+    }
+}
+fn diagram(owner: Id, alias: &str) -> Diagram {
+    Diagram {
+        id: Id::new_v4(),
+        alias: alias.into(),
+        name: alias.into(),
+        description: String::new(),
+        layer: Layer::Oa,
+        projection: ProjectionKind::Scenario { scenario: owner },
+        view_options: Default::default(),
+        nodes: BTreeMap::new(),
+        routes: vec![],
+        layout: None,
+    }
+}
+fn assert_admitted(project: &Project) {
+    let errors: Vec<_> = validation::validate(project)
+        .into_iter()
+        .filter(|issue| issue.severity == validation::Severity::Error)
+        .collect();
+    assert!(errors.is_empty(), "{errors:?}");
+}
+fn has_code(project: &Project, code: &str) -> bool {
+    validation::validate(project)
+        .iter()
+        .any(|issue| issue.code == code)
+}
+fn layout(diagram: &Diagram) -> &ScenarioLayout {
+    let Some(DiagramLayout::Scenario(layout)) = &diagram.layout else {
+        panic!("expected saved payload")
+    };
+    layout
+}
+fn save(project: &mut Project, replacement: Diagram) {
+    project.diagrams.insert(replacement.id, replacement);
+}
+fn fixture() -> Fixture {
+    let mut project = Project::empty();
+    let owner = project
+        .add_element(Kind::Scenario, Layer::Oa, "Nominal", None)
+        .unwrap();
+    let Some(SharedBody::Scenario { viewpoint, .. }) =
+        project.elements.get_mut(&owner).unwrap().shared_mut()
+    else {
+        panic!("Scenario fixture body");
+    };
+    *viewpoint = ScenarioViewpoint::ParticipantInteraction;
+    let performer = project
+        .add_element(Kind::Entity, Layer::Oa, "Controller", None)
+        .unwrap();
+    let receiver = project
+        .add_element(Kind::Entity, Layer::Oa, "Provider", None)
+        .unwrap();
+    let lane = project
+        .add_element(Kind::Lifeline, Layer::Oa, "Controller lane", Some(owner))
+        .unwrap();
+    let repeated_lane = project
+        .add_element(
+            Kind::Lifeline,
+            Layer::Oa,
+            "Controller review lane",
+            Some(owner),
+        )
+        .unwrap();
+    let receiver_lane = project
+        .add_element(Kind::Lifeline, Layer::Oa, "Provider lane", Some(owner))
+        .unwrap();
+    for (id, represented) in [
+        (lane, performer),
+        (repeated_lane, performer),
+        (receiver_lane, receiver),
+    ] {
+        *project.elements.get_mut(&id).unwrap().shared_mut().unwrap() = SharedBody::Lifeline {
+            represented: Some(represented),
+        };
+    }
+    let exchange = Id::new_v4();
+    project.relations.insert(
+        exchange,
+        Relation {
+            id: exchange,
+            alias: "delivery_channel".into(),
+            name: "Delivery".into(),
+            description: String::new(),
+            body: RelationBody::new(RelationKind::CommunicationMean, performer, receiver),
+        },
+    );
+    let first = project
+        .add_element(Kind::Occurrence, Layer::Oa, "First delivery", Some(owner))
+        .unwrap();
+    let second = project
+        .add_element(Kind::Occurrence, Layer::Oa, "Second delivery", Some(owner))
+        .unwrap();
+    for (id, sender) in [(first, lane), (second, repeated_lane)] {
+        set_body(
+            project.elements.get_mut(&id).unwrap(),
+            OccurrenceBody::Exchange {
+                exchange: Some(exchange),
+                sender: Some(sender),
+                receiver: Some(receiver_lane),
+                message_kind: MessageKind::Asynchronous,
+                reply_to: None,
+                values: vec![],
+                operation: None,
+            },
+        );
+    }
+    let fragment = project
+        .add_element(
+            Kind::Occurrence,
+            Layer::Oa,
+            "Optional delivery",
+            Some(owner),
+        )
+        .unwrap();
+    set_body(
+        project.elements.get_mut(&fragment).unwrap(),
+        OccurrenceBody::Fragment {
+            operator: FragmentOperator::Optional,
+            branches: vec![],
+        },
+    );
+    let branch = project
+        .add_element(Kind::Occurrence, Layer::Oa, "Option body", Some(fragment))
+        .unwrap();
+    let nested = project
+        .add_element(
+            Kind::Occurrence,
+            Layer::Oa,
+            "Unfinished nested delivery",
+            Some(branch),
+        )
+        .unwrap();
+    set_body(
+        project.elements.get_mut(&nested).unwrap(),
+        OccurrenceBody::Exchange {
+            exchange: None,
+            sender: None,
+            receiver: None,
+            message_kind: MessageKind::Asynchronous,
+            reply_to: None,
+            values: vec![],
+            operation: None,
+        },
+    );
+    set_body(
+        project.elements.get_mut(&branch).unwrap(),
+        OccurrenceBody::Branch {
+            guard: "requested".into(),
+            occurrences: vec![nested],
+        },
+    );
+    set_body(
+        project.elements.get_mut(&fragment).unwrap(),
+        OccurrenceBody::Fragment {
+            operator: FragmentOperator::Optional,
+            branches: vec![branch],
+        },
+    );
+    *project
+        .elements
+        .get_mut(&owner)
+        .unwrap()
+        .steps_mut()
+        .unwrap() = vec![first, second, fragment];
+    let view_record = diagram(owner, "nominal_view");
+    let other_record = diagram(owner, "review_view");
+    let view = view_record.id;
+    let other_view = other_record.id;
+    save(&mut project, view_record);
+    save(&mut project, other_record);
+    assert_admitted(&project);
+    Fixture {
+        project,
+        owner,
+        performer,
+        lane,
+        repeated_lane,
+        first,
+        second,
+        nested,
+        fragment,
+        branch,
+        view,
+        other_view,
+        exchange,
+    }
+}
+
+#[test]
+fn two_views_and_repeated_semantic_definitions_keep_independent_overrides() {
+    let mut f = fixture();
+    let semantics = (f.project.elements.clone(), f.project.relations.clone());
+    for (view, line, x) in [
+        (f.view, f.lane, 420.),
+        (f.view, f.repeated_lane, 680.),
+        (f.other_view, f.lane, 900.),
+    ] {
+        let result =
+            set_lane(&f.project, view, ScenarioLanePosition { lifeline: line, x }).unwrap();
+        save(&mut f.project, result);
+    }
+    for (view, id, y) in [
+        (f.view, f.first, 200.),
+        (f.view, f.second, 350.),
+        (f.other_view, f.first, 260.),
+    ] {
+        let result = set_message(
+            &f.project,
+            view,
+            ScenarioMessagePosition {
+                address: address(id),
+                send_y: y,
+            },
+        )
+        .unwrap();
+        save(&mut f.project, result);
+    }
+    assert_eq!(
+        layout(&f.project.diagrams[&f.view]).lanes,
+        vec![
+            ScenarioLanePosition {
+                lifeline: f.lane,
+                x: 420.
+            },
+            ScenarioLanePosition {
+                lifeline: f.repeated_lane,
+                x: 680.
+            },
+        ]
+    );
+    assert_eq!(
+        layout(&f.project.diagrams[&f.view])
+            .messages
+            .iter()
+            .map(|r| (r.address.occurrence, r.send_y))
+            .collect::<Vec<_>>(),
+        vec![(f.first, 200.), (f.second, 350.)]
+    );
+    assert_eq!(
+        layout(&f.project.diagrams[&f.other_view]).messages[0].send_y,
+        260.
+    );
+    assert_eq!(layout(&f.project.diagrams[&f.other_view]).lanes[0].x, 900.);
+    assert_eq!(
+        (f.project.elements.clone(), f.project.relations.clone()),
+        semantics
+    );
+    assert_admitted(&f.project);
+}
+
+#[test]
+fn own_nested_unfinished_message_is_admitted_but_expansion_is_not() {
+    let mut f = fixture();
+    let result = set_message(
+        &f.project,
+        f.view,
+        ScenarioMessagePosition {
+            address: address(f.nested),
+            send_y: -80.,
+        },
+    )
+    .unwrap();
+    save(&mut f.project, result);
+    assert_admitted(&f.project);
+    let before = f.project.clone();
+    let expanded = OccurrenceEndpoint {
+        references: vec![f.fragment],
+        occurrence: f.nested,
+    };
+    assert!(
+        set_message(
+            &f.project,
+            f.view,
+            ScenarioMessagePosition {
+                address: expanded.clone(),
+                send_y: 400.
+            }
+        )
+        .is_err()
+    );
+    assert!(remove_message(&f.project, f.view, &expanded).is_err());
+    assert_eq!(f.project, before);
+    payload(f.project.diagrams.get_mut(&f.view).unwrap()).messages[0].address = expanded;
+    assert!(has_code(&f.project, "scenario_layout_address"));
+}
+
+#[test]
+fn only_ordered_message_appearances_and_owned_lifelines_are_targets() {
+    let mut f = fixture();
+    assert!(
+        set_lane(
+            &f.project,
+            f.view,
+            ScenarioLanePosition {
+                lifeline: f.performer,
+                x: 10.
+            }
+        )
+        .is_err()
+    );
+    for id in [f.exchange, f.fragment, f.branch, f.owner, Id::new_v4()] {
+        assert!(
+            set_message(
+                &f.project,
+                f.view,
+                ScenarioMessagePosition {
+                    address: address(id),
+                    send_y: 100.
+                }
+            )
+            .is_err()
+        );
+    }
+    let foreign = f
+        .project
+        .add_element(Kind::Scenario, Layer::Oa, "Foreign", None)
+        .unwrap();
+    let foreign_lane = f
+        .project
+        .add_element(Kind::Lifeline, Layer::Oa, "Foreign lane", Some(foreign))
+        .unwrap();
+    assert!(remove_lane(&f.project, f.view, foreign_lane).is_err());
+    f.project.elements.get_mut(&f.first).unwrap().parent = Some(foreign);
+    assert!(
+        set_message(
+            &f.project,
+            f.view,
+            ScenarioMessagePosition {
+                address: address(f.first),
+                send_y: 100.
+            }
+        )
+        .is_err()
+    );
+    f.project.elements.get_mut(&f.first).unwrap().parent = Some(f.owner);
+    f.project
+        .elements
+        .get_mut(&f.owner)
+        .unwrap()
+        .steps_mut()
+        .unwrap()
+        .retain(|id| *id != f.first);
+    assert!(
+        set_message(
+            &f.project,
+            f.view,
+            ScenarioMessagePosition {
+                address: address(f.first),
+                send_y: 100.
+            }
+        )
+        .is_err()
+    );
+}
+
+#[test]
+fn duplicate_positions_reject_even_when_values_match() {
+    let mut f = fixture();
+    let lane = ScenarioLanePosition {
+        lifeline: f.lane,
+        x: 10.,
+    };
+    let message = ScenarioMessagePosition {
+        address: address(f.first),
+        send_y: 100.,
+    };
+    let entries = payload(f.project.diagrams.get_mut(&f.view).unwrap());
+    entries.lanes = vec![lane.clone(), lane.clone()];
+    entries.messages = vec![message.clone(), message.clone()];
+    assert!(has_code(&f.project, "duplicate_scenario_lane"));
+    assert!(has_code(&f.project, "duplicate_scenario_message"));
+    assert!(set_lane(&f.project, f.view, lane).is_err());
+    assert!(set_message(&f.project, f.view, message).is_err());
+    // Explicit removal can repair all duplicates of the targeted identity.
+    let result = remove_lane(&f.project, f.view, f.lane).unwrap();
+    save(&mut f.project, result);
+    let result = remove_message(&f.project, f.view, &address(f.first)).unwrap();
+    save(&mut f.project, result);
+    assert_admitted(&f.project);
+}
+
+#[test]
+fn sparse_absence_empty_payload_and_signed_zero_are_preserved() {
+    let mut f = fixture();
+    let absent = f.project.diagrams[&f.view].clone();
+    assert_eq!(remove_lane(&f.project, f.view, f.lane).unwrap(), absent);
+    assert_eq!(
+        remove_message(&f.project, f.view, &address(f.first)).unwrap(),
+        absent
+    );
+    assert!(
+        serde_json::to_value(&absent)
+            .unwrap()
+            .get("layout")
+            .is_none()
+    );
+    let result = set_lane(
+        &f.project,
+        f.view,
+        ScenarioLanePosition {
+            lifeline: f.lane,
+            x: -0.,
+        },
+    )
+    .unwrap();
+    save(&mut f.project, result);
+    let result = set_message(
+        &f.project,
+        f.view,
+        ScenarioMessagePosition {
+            address: address(f.first),
+            send_y: -0.,
+        },
+    )
+    .unwrap();
+    save(&mut f.project, result);
+    let result = set_lane(
+        &f.project,
+        f.view,
+        ScenarioLanePosition {
+            lifeline: f.lane,
+            x: 0.,
+        },
+    )
+    .unwrap();
+    assert_eq!(layout(&result).lanes[0].x.to_bits(), (-0.0_f32).to_bits());
+    let result = set_message(
+        &f.project,
+        f.view,
+        ScenarioMessagePosition {
+            address: address(f.first),
+            send_y: 0.,
+        },
+    )
+    .unwrap();
+    assert_eq!(
+        layout(&result).messages[0].send_y.to_bits(),
+        (-0.0_f32).to_bits()
+    );
+    assert_eq!(
+        serde_json::to_string(&result).unwrap(),
+        serde_json::to_string(&f.project.diagrams[&f.view]).unwrap()
+    );
+    let result = remove_lane(&f.project, f.view, f.lane).unwrap();
+    save(&mut f.project, result);
+    let result = remove_message(&f.project, f.view, &address(f.first)).unwrap();
+    assert_eq!(
+        result.layout,
+        Some(DiagramLayout::Scenario(ScenarioLayout::default()))
+    );
+    assert_ne!(result, absent);
+}
+
+#[test]
+fn bounds_are_structural_and_rejected_helpers_do_not_mutate_project() {
+    let mut f = fixture();
+    for value in [-MAX_COORDINATE, MAX_COORDINATE, -7., 0.] {
+        let result = set_lane(
+            &f.project,
+            f.view,
+            ScenarioLanePosition {
+                lifeline: f.lane,
+                x: value,
+            },
+        )
+        .unwrap();
+        save(&mut f.project, result);
+        let result = set_message(
+            &f.project,
+            f.view,
+            ScenarioMessagePosition {
+                address: address(f.first),
+                send_y: value,
+            },
+        )
+        .unwrap();
+        save(&mut f.project, result);
+        assert_admitted(&f.project);
+    }
+    let before = serde_json::to_string(&f.project).unwrap();
+    for value in [
+        f32::NAN,
+        f32::INFINITY,
+        f32::NEG_INFINITY,
+        MAX_COORDINATE + 1.,
+    ] {
+        assert!(
+            set_lane(
+                &f.project,
+                f.view,
+                ScenarioLanePosition {
+                    lifeline: f.lane,
+                    x: value
+                }
+            )
+            .is_err()
+        );
+        assert!(
+            set_message(
+                &f.project,
+                f.view,
+                ScenarioMessagePosition {
+                    address: address(f.first),
+                    send_y: value
+                }
+            )
+            .is_err()
+        );
+    }
+    assert_eq!(serde_json::to_string(&f.project).unwrap(), before);
+    payload(f.project.diagrams.get_mut(&f.view).unwrap()).messages[0].send_y = f32::NAN;
+    assert!(has_code(&f.project, "scenario_layout_coordinate"));
+}
+
+#[test]
+fn helpers_do_not_validate_unrelated_transient_records_in_repair_batches() {
+    let mut f = fixture();
+    payload(f.project.diagrams.get_mut(&f.view).unwrap())
+        .messages
+        .push(ScenarioMessagePosition {
+            address: address(f.second),
+            send_y: f32::INFINITY,
+        });
+    let result = set_lane(
+        &f.project,
+        f.view,
+        ScenarioLanePosition {
+            lifeline: f.lane,
+            x: 420.,
+        },
+    )
+    .unwrap();
+    save(&mut f.project, result);
+    assert!(has_code(&f.project, "scenario_layout_coordinate"));
+    let result = set_message(
+        &f.project,
+        f.view,
+        ScenarioMessagePosition {
+            address: address(f.second),
+            send_y: 300.,
+        },
+    )
+    .unwrap();
+    save(&mut f.project, result);
+    assert_admitted(&f.project);
+}
+
+#[test]
+fn projection_context_and_architecture_payloads_are_explicitly_separate() {
+    let mut f = fixture();
+    let scenario = f.project.diagrams[&f.view].projection;
+    assert_eq!(scenario.scenario(), Some(f.owner));
+    assert!(!scenario.is_architecture());
+    assert!(!scenario.includes(Kind::Lifeline));
+    assert!(ProjectionKind::Overview.is_architecture());
+    assert!(!ProjectionKind::StateMachine { machine: f.owner }.is_architecture());
+    f.project.diagrams.get_mut(&f.view).unwrap().layer = Layer::Sa;
+    assert!(has_code(&f.project, "scenario_diagram_context"));
+    assert!(remove_lane(&f.project, f.view, f.lane).is_err());
+    f.project.diagrams.get_mut(&f.view).unwrap().layer = Layer::Oa;
+    f.project
+        .diagrams
+        .get_mut(&f.view)
+        .unwrap()
+        .routes
+        .push(crate::EdgeRoute {
+            edge: f.exchange,
+            source_attachment: None,
+            target_attachment: None,
+            waypoints: vec![],
+            label: None,
+        });
+    assert!(has_code(&f.project, "scenario_diagram_content"));
+    f.project.diagrams.get_mut(&f.view).unwrap().routes.clear();
+    payload(f.project.diagrams.get_mut(&f.view).unwrap());
+    f.project.diagrams.get_mut(&f.view).unwrap().projection = ProjectionKind::Overview;
+    assert!(has_code(&f.project, "scenario_layout_projection"));
+    assert!(
+        set_lane(
+            &f.project,
+            f.view,
+            ScenarioLanePosition {
+                lifeline: f.lane,
+                x: 10.
+            }
+        )
+        .is_err()
+    );
+}
+
+#[test]
+fn typed_json_records_round_trip_and_reject_unknown_or_missing_fields() {
+    let mut f = fixture();
+    let result = set_message(
+        &f.project,
+        f.view,
+        ScenarioMessagePosition {
+            address: address(f.first),
+            send_y: 200.,
+        },
+    )
+    .unwrap();
+    save(&mut f.project, result);
+    let encoded = serde_json::to_value(&f.project.diagrams[&f.view]).unwrap();
+    assert_eq!(
+        serde_json::from_value::<Diagram>(encoded.clone()).unwrap(),
+        f.project.diagrams[&f.view]
+    );
+    assert_eq!(
+        encoded["layout"]["Scenario"]["messages"][0]["address"]["occurrence"],
+        serde_json::json!(f.first)
+    );
+    let mut unknown = encoded.clone();
+    unknown["layout"]["Scenario"]["messages"][0]["extra"] = serde_json::json!(1);
+    assert!(serde_json::from_value::<Diagram>(unknown).is_err());
+    let mut missing = encoded;
+    missing["layout"]["Scenario"]["messages"][0]["address"]
+        .as_object_mut()
+        .unwrap()
+        .remove("references");
+    assert!(serde_json::from_value::<Diagram>(missing).is_err());
+}
+
+#[test]
+fn deleting_only_actual_ids_preserves_latent_message_positions_and_other_views() {
+    let mut f = fixture();
+    let result = set_lane(
+        &f.project,
+        f.view,
+        ScenarioLanePosition {
+            lifeline: f.lane,
+            x: 420.,
+        },
+    )
+    .unwrap();
+    save(&mut f.project, result);
+    let result = set_message(
+        &f.project,
+        f.view,
+        ScenarioMessagePosition {
+            address: address(f.first),
+            send_y: 200.,
+        },
+    )
+    .unwrap();
+    save(&mut f.project, result);
+    let mut copied = f.project.diagrams[&f.view].clone();
+    copied.id = f.other_view;
+    copied.alias = "review_view".into();
+    copied.name = "Review view".into();
+    save(&mut f.project, copied.clone());
+    assert_admitted(&f.project);
+    assert_eq!(layout(&copied).messages[0].address.occurrence, f.first);
+    let mut candidate = f.project.diagrams[&f.view].clone();
+    prune_deleted(&mut candidate, &BTreeSet::from([f.lane, f.exchange]));
+    assert!(layout(&candidate).lanes.is_empty());
+    assert_eq!(layout(&candidate).messages.len(), 1);
+    prune_deleted(&mut candidate, &BTreeSet::from([f.first]));
+    assert!(layout(&candidate).messages.is_empty());
+    assert!(candidate.layout.is_some());
+    assert_eq!(f.project.diagrams[&f.other_view], copied);
+}
+
+#[test]
+fn reference_visitor_and_record_count_cover_explicit_rows() {
+    let f = fixture();
+    let mut d = f.project.diagrams[&f.view].clone();
+    assert_eq!(record_count(&d), 0);
+    let rows = payload(&mut d);
+    rows.lanes.push(ScenarioLanePosition {
+        lifeline: f.lane,
+        x: 50.,
+    });
+    rows.messages.push(ScenarioMessagePosition {
+        address: address(f.first),
+        send_y: 100.,
+    });
+    assert_eq!(record_count(&d), 3);
+    let replacement = Id::new_v4();
+    d.layout.as_mut().unwrap().visit_references(|id| {
+        if *id == f.first {
+            *id = replacement;
+        }
+    });
+    assert_eq!(layout(&d).messages[0].address.occurrence, replacement);
+    assert_eq!(layout(&d).messages[0].send_y, 100.);
+    assert_eq!(layout(&d).lanes[0].lifeline, f.lane);
+}
+
+#[test]
+fn a_real_scenario_use_never_imports_its_called_message_as_a_direct_target() {
+    let mut f = fixture();
+    let called = f
+        .project
+        .add_element(Kind::Scenario, Layer::Oa, "Called sequence", None)
+        .unwrap();
+    let Some(SharedBody::Scenario { viewpoint, .. }) =
+        f.project.elements.get_mut(&called).unwrap().shared_mut()
+    else {
+        panic!("Called Scenario fixture body");
+    };
+    *viewpoint = ScenarioViewpoint::ParticipantInteraction;
+    let called_message = f
+        .project
+        .add_element(Kind::Occurrence, Layer::Oa, "Called delivery", Some(called))
+        .unwrap();
+    set_body(
+        f.project.elements.get_mut(&called_message).unwrap(),
+        OccurrenceBody::Exchange {
+            exchange: None,
+            sender: None,
+            receiver: None,
+            message_kind: MessageKind::Asynchronous,
+            reply_to: None,
+            values: vec![],
+            operation: None,
+        },
+    );
+    *f.project
+        .elements
+        .get_mut(&called)
+        .unwrap()
+        .steps_mut()
+        .unwrap() = vec![called_message];
+    let usage = f
+        .project
+        .add_element(Kind::Occurrence, Layer::Oa, "Call sequence", Some(f.owner))
+        .unwrap();
+    set_body(
+        f.project.elements.get_mut(&usage).unwrap(),
+        OccurrenceBody::ScenarioUse {
+            scenario: Some(called),
+            bindings: vec![],
+        },
+    );
+    f.project
+        .elements
+        .get_mut(&f.owner)
+        .unwrap()
+        .steps_mut()
+        .unwrap()
+        .push(usage);
+    assert_admitted(&f.project);
+    for target in [
+        address(called_message),
+        address(usage),
+        OccurrenceEndpoint {
+            references: vec![usage],
+            occurrence: called_message,
+        },
+    ] {
+        assert!(
+            set_message(
+                &f.project,
+                f.view,
+                ScenarioMessagePosition {
+                    address: target,
+                    send_y: 200.
+                }
+            )
+            .is_err()
+        );
+    }
+}
+
+mod source_lifecycle;

crates/oa-core/src/scenario_layout/tests/source_lifecycle.rs

@@ -0,0 +1,302 @@
+//! Source/command lifecycle checks for the candidate payload. Public version
+//! assignment remains the coordinated codec integration gate.
+use super::*;
+use crate::{Command, Session, language, prepare_command, source_project::*};
+
+fn authored(f: &Fixture) -> CompiledSourceProject {
+    let mut bundle = format_bundle(&f.project);
+    let initial = compile_bundle(&bundle, ProjectLimits::default()).unwrap();
+    let location = &initial.index.declarations[&f.view];
+    let source = bundle.files.get_mut(&location.path).unwrap();
+    let text = format!(
+        r#"diagram nominal_view "Nominal review" id "{}" {{
+ projection {{ Scenario {{ scenario @{}; }}; }};
+ layout {{ Scenario {{
+  lanes [
+   // Controller spacing rationale.
+   {{ lifeline @ // first lane identity
+      {}; x 4.20e2; }},
+   // Repeated performer has its own lane.
+   {{ lifeline @{}; x 680; }}
+  ];
+  messages [
+   // First delivery timing rationale.
+   {{ address {{ references []; occurrence @{}; }}; send_y 2.00e2; }},
+   // Second delivery timing rationale.
+   {{ address {{ references []; occurrence @{}; }}; send_y 350; }}
+  ];
+ }}; }};
+}}
+"#,
+        f.view,
+        f.project.elements[&f.owner].alias,
+        f.project.elements[&f.lane].alias,
+        f.project.elements[&f.repeated_lane].alias,
+        f.project.elements[&f.first].alias,
+        f.project.elements[&f.second].alias
+    );
+    source.replace_range(location.span.start..location.span.end, &text);
+    compile_bundle(&bundle, ProjectLimits::default()).unwrap()
+}
+
+#[test]
+fn source_rows_follow_identity_order_and_keep_comments_numeric_spelling_and_file_ownership() {
+    let f = fixture();
+    let original = authored(&f);
+    let mut changed = original.decoded.project.clone();
+    let rows = payload(changed.diagrams.get_mut(&f.view).unwrap());
+    rows.lanes.swap(0, 1);
+    rows.messages.swap(0, 1);
+    rows.messages[0].send_y = 390.;
+    changed.elements.get_mut(&f.lane).unwrap().alias = "renamed_controller_lane".into();
+    let updated = update_bundle(&original, &changed, ProjectLimits::default()).unwrap();
+    assert_eq!(updated.decoded.project, changed);
+    let path = &original.index.declarations[&f.view].path;
+    assert_eq!(&updated.index.declarations[&f.view].path, path);
+    let text = &updated.bundle.files[path];
+    assert!(
+        text.find("// Repeated performer").unwrap() < text.find("// Controller spacing").unwrap(),
+        "{text}"
+    );
+    assert!(
+        text.find("// Second delivery").unwrap() < text.find("// First delivery").unwrap(),
+        "{text}"
+    );
+    assert!(
+        text.contains(
+            "lifeline @ // first lane identity\n      renamed_controller_lane; x 4.20e2;"
+        ),
+        "{text}"
+    );
+    assert!(text.contains("send_y 2.00e2"), "{text}");
+    assert!(text.contains("send_y 390"), "{text}");
+    for (other, bytes) in &original.bundle.files {
+        if other != path && !bytes.contains(&f.project.elements[&f.lane].alias) {
+            assert_eq!(&updated.bundle.files[other], bytes);
+        }
+    }
+    assert_eq!(
+        compile_bundle(&updated.bundle, ProjectLimits::default())
+            .unwrap()
+            .decoded
+            .project,
+        changed
+    );
+}
+
+#[test]
+fn source_identity_swap_keeps_each_coordinate_comment_with_its_original_object() {
+    let f = fixture();
+    let original = authored(&f);
+    let temporary = Id::new_v4();
+    let command = Command::Batch(vec![
+        Command::Reidentify(f.first, temporary),
+        Command::Reidentify(f.second, f.first),
+        Command::Reidentify(temporary, f.second),
+    ]);
+    let prepared = prepare_command(&original.decoded.project, &command).unwrap();
+    let mut changed = prepared.project;
+    payload(changed.diagrams.get_mut(&f.view).unwrap())
+        .messages
+        .swap(0, 1);
+    let updated = update_bundle_with_identity_map(
+        &original,
+        &changed,
+        &prepared.identity_map,
+        ProjectLimits::default(),
+    )
+    .unwrap();
+    assert_eq!(updated.decoded.project, changed);
+    let path = &original.index.declarations[&f.view].path;
+    let text = &updated.bundle.files[path];
+    assert!(
+        text.find("// Second delivery").unwrap() < text.find("// First delivery").unwrap(),
+        "{text}"
+    );
+    let first_comment = text.find("// First delivery").unwrap();
+    assert!(text[first_comment..].contains(&format!(
+        "occurrence @{}",
+        changed.elements[&f.second].alias
+    )));
+    assert!(text[first_comment..].contains("send_y 2.00e2"));
+}
+
+#[test]
+fn coordinate_batch_is_one_undo_and_numeric_noop_keeps_source_exact() {
+    let f = fixture();
+    let original = authored(&f);
+    let mut session = Session::new(original.decoded.project.clone());
+    session
+        .execute(Command::Batch(vec![
+            Command::SetScenarioLanePosition {
+                diagram: f.view,
+                position: ScenarioLanePosition {
+                    lifeline: f.lane,
+                    x: 510.,
+                },
+            },
+            Command::SetScenarioMessagePosition {
+                diagram: f.view,
+                position: ScenarioMessagePosition {
+                    address: address(f.second),
+                    send_y: 430.,
+                },
+            },
+        ]))
+        .unwrap();
+    let changed = session.project().clone();
+    assert_eq!(session.revision(), 1);
+    assert_eq!(changed.elements, original.decoded.project.elements);
+    assert_eq!(changed.relations, original.decoded.project.relations);
+    let updated = update_bundle(&original, &changed, ProjectLimits::default()).unwrap();
+    session.undo();
+    assert_eq!(session.project(), &original.decoded.project);
+    assert!(!session.can_undo());
+    session.redo();
+    assert_eq!(session.project(), &changed);
+    session
+        .execute(Command::SetScenarioMessagePosition {
+            diagram: f.view,
+            position: ScenarioMessagePosition {
+                address: address(f.second),
+                send_y: 430.,
+            },
+        })
+        .unwrap();
+    assert_eq!(session.revision(), 3);
+    let noop = update_bundle(&updated, session.project(), ProjectLimits::default()).unwrap();
+    assert_eq!(noop.bundle, updated.bundle);
+}
+
+#[test]
+fn absent_and_empty_payload_round_trip_distinctly_and_remove_does_not_materialize_absence() {
+    let f = fixture();
+    let before = language::format(&f.project);
+    let mut session = Session::new(f.project.clone());
+    session
+        .execute(Command::RemoveScenarioLanePosition {
+            diagram: f.view,
+            lifeline: f.lane,
+        })
+        .unwrap();
+    assert_eq!(session.project(), &f.project);
+    assert!(!session.can_undo());
+    assert_eq!(language::format(session.project()), before);
+    let mut present = f.project.clone();
+    present.diagrams.get_mut(&f.view).unwrap().layout =
+        Some(DiagramLayout::Scenario(ScenarioLayout::default()));
+    let text = language::format(&present);
+    assert_ne!(text, before);
+    assert_eq!(language::parse(&text).unwrap(), present);
+    assert_eq!(language::parse(&before).unwrap(), f.project);
+}
+
+#[test]
+fn invalid_layout_source_rejects_without_changing_last_compiled_workspace() {
+    let f = fixture();
+    let original = authored(&f);
+    let before = original.bundle.clone();
+    let path = original.index.declarations[&f.view].path.clone();
+    for replacement in ["x 1e30", "x not_a_number"] {
+        let mut candidate = before.clone();
+        let source = candidate.files.get_mut(&path).unwrap();
+        *source = source.replace("x 4.20e2", replacement);
+        assert!(compile_bundle(&candidate, ProjectLimits::default()).is_err());
+        assert_eq!(original.bundle, before);
+    }
+    let mut candidate = before.clone();
+    let source = candidate.files.get_mut(&path).unwrap();
+    *source = source.replace(
+        &format!("occurrence @{}", f.project.elements[&f.first].alias),
+        &format!("occurrence @{}", f.project.elements[&f.performer].alias),
+    );
+    assert!(compile_bundle(&candidate, ProjectLimits::default()).is_err());
+    assert_eq!(original.bundle, before);
+}
+
+#[test]
+fn explicit_none_survives_other_edits_while_real_payload_clear_removes_values() {
+    let f = fixture();
+    let mut bundle = format_bundle(&f.project);
+    let compiled = compile_bundle(&bundle, ProjectLimits::default()).unwrap();
+    let location = &compiled.index.declarations[&f.view];
+    let path = location.path.clone();
+    bundle.files.get_mut(&path).unwrap().insert_str(
+        location.span.end - 1,
+        "\n layout // explicitly automatic\n none;\n",
+    );
+    let original = compile_bundle(&bundle, ProjectLimits::default()).unwrap();
+    let mut described = original.decoded.project.clone();
+    described.diagrams.get_mut(&f.view).unwrap().description =
+        "Review spacing independently".into();
+    let updated = update_bundle(&original, &described, ProjectLimits::default()).unwrap();
+    assert!(updated.bundle.files[&path].contains("layout // explicitly automatic\n none;"));
+    assert_eq!(updated.decoded.project, described);
+    let mut empty = described.clone();
+    empty.diagrams.get_mut(&f.view).unwrap().layout =
+        Some(DiagramLayout::Scenario(ScenarioLayout::default()));
+    let present = update_bundle(&updated, &empty, ProjectLimits::default()).unwrap();
+    assert_eq!(present.decoded.project, empty);
+    assert!(present.bundle.files[&path].contains("// explicitly automatic"));
+    let cleared = update_bundle(&present, &described, ProjectLimits::default()).unwrap();
+    assert_eq!(cleared.decoded.project, described);
+    assert!(!cleared.bundle.files[&path].contains("layout"));
+    assert!(cleared.bundle.files[&path].contains("// explicitly automatic"));
+}
+
+#[test]
+fn compact_defaults_and_scenario_row_identity_compose_through_rename_and_clear() {
+    let f = fixture();
+    let initial = authored(&f);
+    let mut bundle = initial.bundle.clone();
+    let location = &initial.index.declarations[&f.performer];
+    bundle.files.get_mut(&location.path).unwrap().insert_str(
+        location.span.end - 1,
+        "\n description // explicitly default prose\n \"\";\n",
+    );
+    let original = compile_bundle(&bundle, ProjectLimits::default()).unwrap();
+    let mut expected = original.decoded.project.clone();
+    let performer = expected.elements.get_mut(&f.performer).unwrap();
+    performer.name = "Reviewed controller".into();
+    performer.alias = "reviewed_controller".into();
+    expected.elements.get_mut(&f.lane).unwrap().alias = "reviewed_lane".into();
+    let rows = payload(expected.diagrams.get_mut(&f.view).unwrap());
+    rows.lanes.swap(0, 1);
+    rows.messages.swap(0, 1);
+    rows.messages[0].send_y = 390.;
+    let updated = update_bundle(&original, &expected, ProjectLimits::default()).unwrap();
+    assert_eq!(updated.decoded.project, expected);
+    let element = &updated.index.declarations[&f.performer];
+    let text = &updated.bundle.files[&element.path][element.span.start..element.span.end];
+    assert!(
+        text.contains("description // explicitly default prose\n \"\";"),
+        "{text}"
+    );
+    assert!(
+        !text.contains("categories"),
+        "an omitted default must stay omitted: {text}"
+    );
+    let diagram = &updated.index.declarations[&f.view];
+    let text = &updated.bundle.files[&diagram.path][diagram.span.start..diagram.span.end];
+    assert!(
+        text.find("// Repeated performer").unwrap() < text.find("// Controller spacing").unwrap()
+    );
+    assert!(text.contains("reviewed_lane; x 4.20e2;"), "{text}");
+    assert!(text.find("// Second delivery").unwrap() < text.find("// First delivery").unwrap());
+    assert!(text.contains("send_y 2.00e2"), "{text}");
+    assert!(!text.contains("view_options"), "{text}");
+    expected.diagrams.get_mut(&f.view).unwrap().layout = None;
+    let cleared = update_bundle(&updated, &expected, ProjectLimits::default()).unwrap();
+    assert_eq!(cleared.decoded.project, expected);
+    let declaration = &cleared.index.declarations[&f.view];
+    let text =
+        &cleared.bundle.files[&declaration.path][declaration.span.start..declaration.span.end];
+    assert!(!text.contains("layout"), "{text}");
+    assert!(text.contains("// Controller spacing rationale."), "{text}");
+    assert_eq!(
+        update_bundle(&cleared, &expected, ProjectLimits::default())
+            .unwrap()
+            .bundle,
+        cleared.bundle,
+    );
+}

crates/oa-core/src/session.rs

@@ -23,6 +23,22 @@ pub enum Command {
     EditRelation(Id, Relation),
     CreateDiagram(Diagram),
     EditDiagram(Id, Diagram),
+    SetScenarioLanePosition {
+        diagram: Id,
+        position: ScenarioLanePosition,
+    },
+    RemoveScenarioLanePosition {
+        diagram: Id,
+        lifeline: Id,
+    },
+    SetScenarioMessagePosition {
+        diagram: Id,
+        position: ScenarioMessagePosition,
+    },
+    RemoveScenarioMessagePosition {
+        diagram: Id,
+        address: OccurrenceEndpoint,
+    },
     CreateArtifact(ArtifactLink),
     EditArtifact(Id, ArtifactLink),
     CreateTrace(Trace),
@@ -488,6 +504,26 @@ fn apply_command(
             reidentify_tracked(p, *old, value.id, provenance)?;
             Some(value.id)
         }
+        Command::SetScenarioLanePosition { diagram, position } => {
+            let replacement = crate::scenario_layout::set_lane(p, *diagram, position.clone())?;
+            p.diagrams.insert(*diagram, replacement);
+            Some(*diagram)
+        }
+        Command::RemoveScenarioLanePosition { diagram, lifeline } => {
+            let replacement = crate::scenario_layout::remove_lane(p, *diagram, *lifeline)?;
+            p.diagrams.insert(*diagram, replacement);
+            Some(*diagram)
+        }
+        Command::SetScenarioMessagePosition { diagram, position } => {
+            let replacement = crate::scenario_layout::set_message(p, *diagram, position.clone())?;
+            p.diagrams.insert(*diagram, replacement);
+            Some(*diagram)
+        }
+        Command::RemoveScenarioMessagePosition { diagram, address } => {
+            let replacement = crate::scenario_layout::remove_message(p, *diagram, address)?;
+            p.diagrams.insert(*diagram, replacement);
+            Some(*diagram)
+        }
         Command::CreateArtifact(value) => {
             vacant(p, value.id)?;
             p.artifact_links.insert(value.id, value.clone());
@@ -878,6 +914,7 @@ pub fn reidentify(p: &mut Project, old: Id, new: Id) -> Result<(), ModelError> {
         return Ok(());
     }
     vacant(p, new)?;
+    crate::references::check_remap(p, old, new)?;
     if p.id == old {
         p.id = new;
     } else if let Some(mut v) = p.elements.remove(&old) {
@@ -904,12 +941,17 @@ pub fn reidentify(p: &mut Project, old: Id, new: Id) -> Result<(), ModelError> {
             }
         }
     }
-    crate::references::remap_references(p, old, new);
+    crate::references::remap_references(p, old, new)?;
     Ok(())
 }
 fn layout(p: &mut Project, diagram: Id) -> Result<(), ModelError> {
     use std::collections::{BTreeMap, BTreeSet};
     let d = p.diagrams.get(&diagram).ok_or_else(missing)?;
+    if d.projection.scenario().is_some() {
+        return Err(ModelError(
+            "Scenario layout requires the Scenario geometry operation.".into(),
+        ));
+    }
     let parents = crate::projection::parents(p, d);
     let mut children: BTreeMap<Option<Id>, Vec<Id>> = BTreeMap::new();
     for (id, parent) in &parents {

crates/oa-core/src/source_defaults.rs

@@ -0,0 +1,405 @@
+//! Ordinary source defaults shared by current parsing and declaration rendering.
+//!
+//! These are source omission defaults, not graphical creation defaults. The
+//! policy operates on complete typed declaration maps. Required named fields
+//! and selected constructor payloads remain distinct from omission defaults.
+//! Historical versions use their existing frozen parser paths. Semantic baseline
+//! history is never traversed or normalized here.
+use crate::{Kind, RelationKind};
+use serde_json::{Map, Value, json};
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub(crate) enum Context {
+    Element(Kind),
+    Relation(RelationKind),
+    Diagram,
+    Node,
+    Artifact,
+    Trace,
+}
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub(crate) enum Mode {
+    CompleteForEdit,
+    Compact,
+    /// Internal lossless-edit fragments: retain every top-level value while
+    /// compacting its selected constructor's optional nested fields.
+    CompactValues,
+}
+
+/// Top-level field inventory for the current ordinary reader. Callers must
+/// check required fields before merging; null entries only admit their names.
+/// This never supplies defaults inside a selected constructor.
+pub(crate) fn parser_fields(context: Context) -> Map<String, Value> {
+    let mut fields = declaration_defaults(context);
+    let required: &[&str] = match context {
+        Context::Element(kind) => {
+            fields.remove("description");
+            fields.remove("parent");
+            if kind == Kind::Port {
+                &["contract"]
+            } else {
+                &[]
+            }
+        }
+        Context::Relation(kind) => {
+            fields.remove("description");
+            match kind {
+                RelationKind::ContextualLink => &["owner", "source", "target", "purpose"],
+                RelationKind::FunctionalExchange => {
+                    &["source", "target", "source_port", "target_port"]
+                }
+                _ => &["source", "target"],
+            }
+        }
+        Context::Diagram => {
+            // Admit the optional payload without restoring a synthetic null in
+            // CompleteForEdit: absence there distinguishes a real layout clear
+            // from an unrelated edit beside an authored explicit `layout none`.
+            fields.insert("layout".into(), Value::Null);
+            &[]
+        }
+        Context::Node => &["element"],
+        Context::Artifact => &["owner"],
+        Context::Trace => &["oa", "sa"],
+    };
+    for name in required {
+        fields.insert((*name).into(), Value::Null);
+    }
+    fields
+}
+
+pub(crate) fn fields(
+    context: Context,
+    input: &Map<String, Value>,
+    mode: Mode,
+) -> Map<String, Value> {
+    let mut result = input.clone();
+    restore_serialization_skips(context, &mut result);
+    if mode != Mode::CompleteForEdit {
+        compact_nested(context, &mut result);
+    }
+    if mode == Mode::Compact {
+        // Compact a composite and its declared default by the same nested rules
+        // before whole-field comparison. This also makes compact input stable:
+        // e.g. String{minimum_length:0} still denotes the default definition.
+        let mut defaults = declaration_defaults(context);
+        compact_nested(context, &mut defaults);
+        omit_defaults(&mut result, &defaults);
+    }
+    result
+}
+
+fn restore_serialization_skips(context: Context, fields: &mut Map<String, Value>) {
+    match context {
+        Context::Element(Kind::Occurrence) => {
+            if let Some(exchange) = constructor_payload(fields, "body", "Exchange") {
+                exchange
+                    .entry("operation".to_owned())
+                    .or_insert(Value::Null);
+            }
+        }
+        Context::Diagram => {
+            if let Some(routes) = fields.get_mut("routes").and_then(Value::as_array_mut) {
+                for route in routes.iter_mut().filter_map(Value::as_object_mut) {
+                    route
+                        .entry("source_attachment".to_owned())
+                        .or_insert(Value::Null);
+                    route
+                        .entry("target_attachment".to_owned())
+                        .or_insert(Value::Null);
+                }
+            }
+        }
+        Context::Node => {
+            fields.entry("port_anchors".to_owned()).or_insert(json!([]));
+        }
+        Context::Trace => {
+            if let Some(baseline) = fields.get_mut("baseline").and_then(Value::as_object_mut) {
+                baseline.entry("semantic".to_owned()).or_insert(Value::Null);
+            }
+        }
+        _ => {}
+    }
+}
+
+fn declaration_defaults(context: Context) -> Map<String, Value> {
+    let mut defaults = match context {
+        Context::Element(kind) => element_defaults(kind),
+        Context::Relation(kind) => relation_defaults(kind),
+        Context::Diagram => object(json!({
+            "description": "", "layer": "Oa", "projection": "Overview",
+            "routes": [], "view_options": {
+                "hidden_edges": [], "relation_kinds": "All",
+                "work_categories": "All", "participant_categories": "All",
+                "coverage": "All", "work_contexts": "All", "exchange_labels": "Name"
+            }
+        })),
+        Context::Node => object(json!({
+            "position": {"x": 0.0, "y": 0.0},
+            "size": {"width": 224.0, "height": 94.0},
+            "collapsed": false, "port_anchors": []
+        })),
+        Context::Artifact => object(json!({
+            "description": "", "relation": "References", "uri": "",
+            "revision": null, "fragment": null
+        })),
+        Context::Trace => object(json!({
+            "description": "", "kind": "Refinement", "baseline": null
+        })),
+    };
+    match context {
+        Context::Element(_) => {
+            defaults.insert("description".into(), json!(""));
+            defaults.insert("parent".into(), Value::Null);
+        }
+        Context::Relation(_) => {
+            defaults.insert("description".into(), json!(""));
+        }
+        _ => {}
+    }
+    defaults
+}
+
+fn element_defaults(kind: Kind) -> Map<String, Value> {
+    if let Some(state_kind) = kind.state_kind() {
+        // The declaration selects this discriminator; no GUI factory is used.
+        return object(json!({
+            "kind": state_kind, "entry": "", "exit": "", "do_activity": ""
+        }));
+    }
+    match kind {
+        Kind::Process | Kind::FunctionalChain => object(json!({"steps": []})),
+        Kind::ExchangeItem => object(json!({
+            "kind": "Information", "mechanism": "Unspecified", "supertype": null
+        })),
+        Kind::ExchangeCategory => object(json!({"family": "Work", "exchanges": []})),
+        Kind::DataType => object(json!({
+            "definition": {"String": {"minimum_length": 0, "maximum_length": null}},
+            "default": null, "unit": ""
+        })),
+        Kind::DataField => object(json!({
+            "type_ref": "String", "minimum": 1, "maximum": 1, "unit": "",
+            "direction": "Unspecified", "storage": "Value", "default": null
+        })),
+        Kind::Interface => object(json!({"supertype": null})),
+        // Port.contract is required, even when its explicit value is Legacy.
+        Kind::Port => object(json!({"legacy": null})),
+        Kind::Scenario => object(json!({
+            "viewpoint": "MixedLegacy", "context": null,
+            "precondition": "", "postcondition": "", "steps": []
+        })),
+        Kind::Lifeline => object(json!({"represented": null})),
+        Kind::Occurrence => object(json!({
+            "body": {"Exchange": {
+                "exchange": null, "sender": null, "receiver": null,
+                "message_kind": "Asynchronous", "reply_to": null,
+                "values": [], "operation": null
+            }},
+            "precondition": "", "postcondition": ""
+        })),
+        Kind::Event => object(json!({"body": {"Signal": {"items": []}}})),
+        Kind::Constraint => object(json!({"expression": "", "constrained": []})),
+        // Unit-body declarations have no additional omission defaults. A future
+        // Kind reaches this branch without gaining speculative payload rules.
+        _ => Map::new(),
+    }
+}
+
+fn relation_defaults(kind: RelationKind) -> Map<String, Value> {
+    match kind {
+        RelationKind::InterfaceItemAllocation => object(json!({
+            "order": 0, "transmission": "Unspecified", "acquisition": "Unspecified"
+        })),
+        RelationKind::DataAssociation => object(json!({
+            "source_role": "", "target_role": "",
+            "source_minimum": 0, "target_minimum": 0,
+            "source_maximum": null, "target_maximum": null,
+            "source_navigable": false, "target_navigable": false
+        })),
+        RelationKind::Interaction | RelationKind::FunctionalExchange => {
+            object(json!({"items": []}))
+        }
+        RelationKind::BoundaryExchange => object(json!({"items": [], "oriented": true})),
+        RelationKind::CommunicationMean => object(json!({"items": [], "oriented": false})),
+        RelationKind::CapabilityExtend => object(json!({"condition": ""})),
+        RelationKind::SequenceLink => object(json!({"guard": ""})),
+        RelationKind::StateTransition => object(json!({
+            "transition_kind": "External", "trigger": "", "guard": "", "effect": "",
+            "triggers": [], "effects": []
+        })),
+        RelationKind::StateAction => object(json!({"phase": "Do"})),
+        // source/target, FunctionalExchange ports and ContextualLink's owner,
+        // endpoints and purpose are required, despite factory placeholder values.
+        _ => Map::new(),
+    }
+}
+
+fn compact_nested(context: Context, fields: &mut Map<String, Value>) {
+    match context {
+        Context::Element(Kind::DataType) => compact_data_definition(fields),
+        Context::Element(Kind::Port) => {
+            if let Some(legacy) = fields.get_mut("legacy").and_then(Value::as_object_mut) {
+                omit_nulls(legacy, &["interface"]);
+            }
+            // Every selected PortContract payload field remains required.
+        }
+        Context::Element(Kind::Occurrence) => compact_occurrence(fields),
+        Context::Diagram => {
+            if let Some(options) = fields
+                .get_mut("view_options")
+                .and_then(Value::as_object_mut)
+            {
+                omit_defaults(
+                    options,
+                    &object(json!({
+                        "hidden_edges": [], "relation_kinds": "All",
+                        "work_categories": "All", "participant_categories": "All",
+                        "coverage": "All", "work_contexts": "All", "exchange_labels": "Name"
+                    })),
+                );
+            }
+            if let Some(routes) = fields.get_mut("routes").and_then(Value::as_array_mut) {
+                for route in routes {
+                    if let Some(route) = route.as_object_mut() {
+                        omit_defaults(
+                            route,
+                            &object(
+                                json!({"waypoints": [], "label": null, "source_attachment": null, "target_attachment": null}),
+                            ),
+                        );
+                    }
+                }
+            }
+            // Route entries, EdgeLabel coordinates, projection machine IDs, and
+            // Only([])/Any([]) selectors remain even when their values are empty.
+        }
+        Context::Trace => {
+            if let Some(baseline) = fields.get_mut("baseline").and_then(Value::as_object_mut) {
+                omit_nulls(baseline, &["semantic"]);
+            }
+            // No recursion through snapshots or semantic historical facets.
+        }
+        // DataValue/TypeRef payloads, EventBody fields, Node geometry/anchors,
+        // contextual endpoints/purposes, and other required records stay intact.
+        _ => {}
+    }
+}
+
+fn compact_data_definition(fields: &mut Map<String, Value>) {
+    for tag in ["Integer", "Real"] {
+        if let Some(payload) = constructor_payload(fields, "definition", tag) {
+            omit_nulls(payload, &["minimum", "maximum"]);
+        }
+    }
+    if let Some(payload) = constructor_payload(fields, "definition", "String") {
+        omit_nulls(payload, &["maximum_length"]);
+        // minimum_length is required inside a selected String constructor.
+    }
+    if let Some(payload) = constructor_payload(fields, "definition", "Record") {
+        omit_nulls(payload, &["supertype"]);
+    }
+    // Boolean has no payload; Enumeration.literals remains required even [].
+}
+
+fn compact_occurrence(fields: &mut Map<String, Value>) {
+    if let Some(exchange) = constructor_payload(fields, "body", "Exchange") {
+        omit_defaults(
+            exchange,
+            &object(json!({
+                "exchange": null, "sender": null, "receiver": null,
+                "message_kind": "Asynchronous", "reply_to": null,
+                "values": [], "operation": null
+            })),
+        );
+        if let Some(operation) = exchange.get_mut("operation").and_then(Value::as_object_mut) {
+            omit_nulls(operation, &["allocation"]);
+            // Keep the containing operation field even if its record becomes {}:
+            // explicit unresolved operation intent is not an absent operation.
+        }
+        if let Some(values) = exchange.get_mut("values").and_then(Value::as_array_mut) {
+            for value in values {
+                if let Some(message_value) = value.as_object_mut() {
+                    omit_defaults(message_value, &object(json!({"path": []})));
+                }
+            }
+        }
+        // MessageKind::Timer.expression, MessageValue.field/expression remain.
+    }
+    for (tag, optional) in [
+        ("Action", &["action", "lifeline"][..]),
+        ("State", &["state", "lifeline"][..]),
+        ("SequenceReference", &["sequence"][..]),
+        ("ScenarioUse", &["scenario"][..]),
+    ] {
+        if let Some(payload) = constructor_payload(fields, "body", tag) {
+            omit_nulls(payload, optional);
+        }
+    }
+    // ScenarioUse.bindings, Control.kind, Fragment.operator/branches and
+    // Branch.guard/occurrences are required, including empty strings/lists.
+}
+
+fn constructor_payload<'a>(
+    fields: &'a mut Map<String, Value>,
+    key: &str,
+    tag: &str,
+) -> Option<&'a mut Map<String, Value>> {
+    let wrapper = fields.get_mut(key)?.as_object_mut()?;
+    if wrapper.len() != 1 {
+        return None;
+    }
+    wrapper.get_mut(tag)?.as_object_mut()
+}
+
+fn omit_nulls(fields: &mut Map<String, Value>, names: &[&str]) {
+    for name in names {
+        if fields.get(*name).is_some_and(Value::is_null) {
+            fields.remove(*name);
+        }
+    }
+}
+
+fn omit_defaults(fields: &mut Map<String, Value>, defaults: &Map<String, Value>) {
+    for (name, default) in defaults {
+        if fields.get(name).is_some_and(|value| same(value, default)) {
+            fields.remove(name);
+        }
+    }
+}
+
+// Comparison recurses only to compare a known field with its exact declared
+// default. It never traverses arbitrary data looking for values to remove.
+fn same(value: &Value, default: &Value) -> bool {
+    match (value, default) {
+        (Value::Object(a), Value::Object(b)) => {
+            a.len() == b.len()
+                && a.iter()
+                    .all(|(key, value)| b.get(key).is_some_and(|d| same(value, d)))
+        }
+        (Value::Array(a), Value::Array(b)) => {
+            a.len() == b.len() && a.iter().zip(b).all(|(value, d)| same(value, d))
+        }
+        (Value::Number(a), Value::Number(b)) => {
+            // serde_json numeric equality alone can equate -0.0 with +0.0.
+            // Extracted f32 coordinates are represented exactly as f64 here.
+            a == b
+                && match (a.as_f64(), b.as_f64()) {
+                    (Some(x), Some(y)) if x == 0.0 && y == 0.0 => x.to_bits() == y.to_bits(),
+                    _ => true,
+                }
+        }
+        _ => value == default,
+    }
+}
+
+fn object(value: Value) -> Map<String, Value> {
+    match value {
+        Value::Object(fields) => fields,
+        _ => unreachable!("literal source default is an object"),
+    }
+}
+
+#[cfg(test)]
+#[path = "source_defaults_tests.rs"]
+mod tests;

crates/oa-core/src/source_defaults_tests.rs

@@ -0,0 +1,718 @@
+//! Independent literal oracles for the production source-default policy.
+use super::{self as policy, Context, Mode};
+use crate::{Kind, RelationKind};
+use serde_json::{Value, json};
+
+#[test]
+fn complete_comparison_keeps_populated_serializer_skip_values() {
+    for (context, input) in [
+        (
+            Context::Element(Kind::Occurrence),
+            json!({"body":{"Exchange":{"operation":{"allocation":"allocation-id"},"values":[]}}}),
+        ),
+        (
+            Context::Node,
+            json!({"port_anchors":[{"port":"port-id","side":"Left","offset":0.0}]}),
+        ),
+        (
+            Context::Trace,
+            json!({"baseline":{"semantic":{"historical":"payload"}}}),
+        ),
+    ] {
+        assert_eq!(rendered(context, &input, Mode::CompleteForEdit), input);
+    }
+}
+
+#[test]
+fn compact_value_fragments_keep_selected_constructor_requirements() {
+    for (context, input, expected) in [
+        (
+            Context::Element(Kind::DataType),
+            json!({"definition":{"String":{"minimum_length":0,"maximum_length":null}},"default":null,"unit":""}),
+            json!({"definition":{"String":{"minimum_length":0}},"default":null,"unit":""}),
+        ),
+        (
+            Context::Element(Kind::Event),
+            json!({"body":{"Signal":{"items":[]}}}),
+            json!({"body":{"Signal":{"items":[]}}}),
+        ),
+        (
+            Context::Element(Kind::Occurrence),
+            json!({"body":{"Exchange":{"operation":{"allocation":null},"values":[]}},"precondition":""}),
+            json!({"body":{"Exchange":{"operation":{}}},"precondition":""}),
+        ),
+        (
+            Context::Element(Kind::Occurrence),
+            json!({"body":{"ScenarioUse":{"scenario":null,"bindings":[]}}}),
+            json!({"body":{"ScenarioUse":{"bindings":[]}}}),
+        ),
+    ] {
+        assert_eq!(rendered(context, &input, Mode::CompactValues), expected);
+    }
+}
+
+#[test]
+fn source_scenario_default_is_independent_of_graphical_creation() {
+    use crate::{ElementBody, Layer, ScenarioViewpoint, SharedBody, language};
+    let project = language::parse(
+        "arcadia 7; project p \"P\" { oa_scenario o \"O\" {} sa_scenario s \"S\" {} }",
+    )
+    .unwrap();
+    for element in project.elements.values() {
+        assert!(matches!(
+            element.body.shared(),
+            Some(SharedBody::Scenario {
+                viewpoint: ScenarioViewpoint::MixedLegacy,
+                ..
+            })
+        ));
+        assert!(!matches!(
+            ElementBody::new(Kind::Scenario, element.layer())
+                .unwrap()
+                .shared(),
+            Some(SharedBody::Scenario {
+                viewpoint: ScenarioViewpoint::MixedLegacy,
+                ..
+            })
+        ));
+    }
+    let source = language::format(&project);
+    assert!(!source.contains("description"));
+    assert!(!source.contains("parent"));
+    assert!(!source.contains("viewpoint"));
+    assert_eq!(language::parse(&source).unwrap(), project);
+
+    let mut typed = project;
+    for element in typed.elements.values_mut() {
+        let viewpoint = if element.layer() == Layer::Oa {
+            ScenarioViewpoint::OperationalActivity
+        } else {
+            ScenarioViewpoint::Functional
+        };
+        *element.body.shared_mut().unwrap() = SharedBody::Scenario {
+            viewpoint,
+            context: None,
+            precondition: String::new(),
+            postcondition: String::new(),
+            steps: vec![],
+        };
+    }
+    let source = language::format(&typed);
+    assert!(source.contains("viewpoint OperationalActivity;"));
+    assert!(source.contains("viewpoint Functional;"));
+    assert_eq!(language::parse(&source).unwrap(), typed);
+}
+
+#[test]
+fn shared_parser_defaults_preserve_required_fields_and_kind_checks() {
+    for (declaration, message) in [
+        (
+            "oa_port p0 \"Port\" {}",
+            "Missing required field 'contract'",
+        ),
+        (
+            "allocation r \"R\" { source @owner; }",
+            "Missing required field 'target'",
+        ),
+        (
+            "functional_exchange r \"R\" { source @owner; target @work; }",
+            "Missing required field 'source_port'",
+        ),
+        (
+            "contextual_link r \"R\" {}",
+            "Missing required field 'owner'",
+        ),
+        ("node n { diagram @d; }", "Missing required field 'element'"),
+        ("artifact a \"A\" {}", "Missing required field 'owner'"),
+        ("trace t \"T\" {}", "Missing required field 'oa'"),
+        (
+            "oa_state s \"S\" { kind Initial; }",
+            "Declaration kind disagrees",
+        ),
+        (
+            "oa_activity a \"A\" { unknown true; }",
+            "Unknown field 'unknown'",
+        ),
+        (
+            "oa_data_type t \"T\" { definition { String {}; }; }",
+            "minimum_length",
+        ),
+        (
+            "oa_occurrence o \"O\" { body { ScenarioUse {}; }; }",
+            "bindings",
+        ),
+    ] {
+        let source = format!(
+            "arcadia 7; project p \"P\" {{ oa_entity owner \"Owner\" {{}} oa_activity work \"Work\" {{}} diagram d \"D\" {{}} {declaration} }}"
+        );
+        let errors = crate::language::parse(&source).unwrap_err();
+        assert!(
+            errors.iter().any(|error| error.message.contains(message)),
+            "{declaration}: {errors:?}"
+        );
+    }
+}
+
+fn rendered(context: Context, input: &Value, mode: Mode) -> Value {
+    Value::Object(policy::fields(context, input.as_object().unwrap(), mode))
+}
+
+fn compact(context: Context, input: Value, expected: Value) {
+    let original = input.clone();
+    let result = rendered(context, &input, Mode::Compact);
+    assert_eq!(result, expected, "context {context:?}");
+    assert_eq!(input, original, "the input remains immutable");
+    assert_eq!(
+        rendered(context, &result, Mode::Compact),
+        result,
+        "compact policy is idempotent"
+    );
+}
+
+#[test]
+fn complete_comparison_restores_only_the_three_known_skips() {
+    let exchange = json!({"body":{"Exchange":{"exchange":null,"sender":null,"receiver":null,"message_kind":"Asynchronous","reply_to":null,"values":[]}}});
+    let mut complete = exchange.clone();
+    complete["body"]["Exchange"]["operation"] = Value::Null;
+    assert_eq!(
+        rendered(
+            Context::Element(Kind::Occurrence),
+            &exchange,
+            Mode::CompleteForEdit
+        ),
+        complete
+    );
+    assert_eq!(
+        rendered(
+            Context::Node,
+            &json!({"element":"e","diagram":"d"}),
+            Mode::CompleteForEdit
+        ),
+        json!({"element":"e","diagram":"d","port_anchors":[]})
+    );
+    assert_eq!(
+        rendered(
+            Context::Trace,
+            &json!({"baseline":{"oa":{"name":"","description":""},"sa":{"name":"","description":""}}}),
+            Mode::CompleteForEdit
+        ),
+        json!({"baseline":{"oa":{"name":"","description":""},"sa":{"name":"","description":""},"semantic":null}})
+    );
+    for input in [
+        json!({"body":{"Action":{"action":null,"lifeline":null}}}),
+        json!({"body":{"State":{"state":null,"lifeline":null}}}),
+    ] {
+        assert_eq!(
+            rendered(
+                Context::Element(Kind::Occurrence),
+                &input,
+                Mode::CompleteForEdit
+            ),
+            input
+        );
+    }
+    for input in [
+        json!({"baseline":null}),
+        json!({"baseline":{"semantic":{"historical":[null,[],false,0,""]},"oa":{"name":"n","description":""},"sa":{"name":"s","description":""}}}),
+    ] {
+        assert_eq!(
+            rendered(Context::Trace, &input, Mode::CompleteForEdit),
+            input
+        );
+    }
+}
+
+#[test]
+fn every_element_omits_only_empty_common_defaults() {
+    for kind in Kind::ALL {
+        // Future/unknown payloads are preservation sentinels, not admitted source.
+        compact(
+            Context::Element(kind),
+            json!({"description":"","parent":null,"future":{"empty":[],"absent":null,"zero":0,"flag":false}}),
+            json!({"future":{"empty":[],"absent":null,"zero":0,"flag":false}}),
+        );
+        compact(
+            Context::Element(kind),
+            json!({"description":" \n","parent":"owner"}),
+            json!({"description":" \n","parent":"owner"}),
+        );
+    }
+}
+
+#[test]
+fn ordinary_element_defaults_are_context_specific() {
+    for kind in [Kind::Process, Kind::FunctionalChain] {
+        compact(Context::Element(kind), json!({"steps":[]}), json!({}));
+        compact(
+            Context::Element(kind),
+            json!({"steps":["second","first"]}),
+            json!({"steps":["second","first"]}),
+        );
+    }
+    compact(
+        Context::Element(Kind::ExchangeItem),
+        json!({"kind":"Information","mechanism":"Unspecified","supertype":null}),
+        json!({}),
+    );
+    compact(
+        Context::Element(Kind::ExchangeItem),
+        json!({"kind":"Energy","mechanism":"Flow","supertype":"base"}),
+        json!({"kind":"Energy","mechanism":"Flow","supertype":"base"}),
+    );
+    compact(
+        Context::Element(Kind::ExchangeCategory),
+        json!({"family":"Work","exchanges":[]}),
+        json!({}),
+    );
+    compact(
+        Context::Element(Kind::ExchangeCategory),
+        json!({"family":"Participant","exchanges":["x"]}),
+        json!({"family":"Participant","exchanges":["x"]}),
+    );
+    compact(
+        Context::Element(Kind::Interface),
+        json!({"supertype":null}),
+        json!({}),
+    );
+    compact(
+        Context::Element(Kind::Lifeline),
+        json!({"represented":null}),
+        json!({}),
+    );
+    compact(
+        Context::Element(Kind::Constraint),
+        json!({"expression":"","constrained":[]}),
+        json!({}),
+    );
+}
+
+#[test]
+fn scenario_source_default_never_uses_the_graphical_viewpoint_default() {
+    compact(
+        Context::Element(Kind::Scenario),
+        json!({"viewpoint":"MixedLegacy","context":null,"precondition":"","postcondition":"","steps":[]}),
+        json!({}),
+    );
+    for viewpoint in [
+        "OperationalActivity",
+        "Functional",
+        "ParticipantInteraction",
+        "BoundaryInterface",
+    ] {
+        compact(
+            Context::Element(Kind::Scenario),
+            json!({"viewpoint":viewpoint,"context":"scope","precondition":"ready","postcondition":"","steps":["two","one"]}),
+            json!({"viewpoint":viewpoint,"context":"scope","precondition":"ready","steps":["two","one"]}),
+        );
+    }
+}
+
+#[test]
+fn each_state_header_supplies_its_own_kind() {
+    for (kind, name) in [
+        (Kind::State, "State"),
+        (Kind::Mode, "Mode"),
+        (Kind::Initial, "Initial"),
+        (Kind::Final, "Final"),
+        (Kind::Choice, "Choice"),
+        (Kind::Junction, "Junction"),
+        (Kind::Fork, "Fork"),
+        (Kind::Join, "Join"),
+        (Kind::ShallowHistory, "ShallowHistory"),
+        (Kind::DeepHistory, "DeepHistory"),
+        (Kind::EntryPoint, "EntryPoint"),
+        (Kind::ExitPoint, "ExitPoint"),
+        (Kind::Terminate, "Terminate"),
+    ] {
+        compact(
+            Context::Element(kind),
+            json!({"kind":name,"entry":"","exit":"","do_activity":""}),
+            json!({}),
+        );
+    }
+    // Invalid mismatches must not be silently normalized by the writer policy.
+    compact(
+        Context::Element(Kind::Mode),
+        json!({"kind":"State","entry":"work"}),
+        json!({"kind":"State","entry":"work"}),
+    );
+}
+
+#[test]
+fn data_field_unbounded_and_present_empty_values_are_not_defaults() {
+    compact(
+        Context::Element(Kind::DataField),
+        json!({"type_ref":"String","minimum":1,"maximum":1,"unit":"","direction":"Unspecified","storage":"Value","default":null}),
+        json!({}),
+    );
+    compact(
+        Context::Element(Kind::DataField),
+        json!({"type_ref":{"Named":"record"},"minimum":0,"maximum":null,"unit":"m","direction":"Out","storage":"Reference","default":[]}),
+        json!({"type_ref":{"Named":"record"},"minimum":0,"maximum":null,"unit":"m","direction":"Out","storage":"Reference","default":[]}),
+    );
+    for value in [
+        json!({"Boolean":false}),
+        json!({"Integer":0}),
+        json!({"Real":0.0}),
+        json!({"String":""}),
+    ] {
+        compact(
+            Context::Element(Kind::DataField),
+            json!({"default":[value.clone()]}),
+            json!({"default":[value]}),
+        );
+    }
+}
+
+#[test]
+fn data_definition_whole_default_and_selected_required_fields_differ() {
+    compact(
+        Context::Element(Kind::DataType),
+        json!({"definition":{"String":{"minimum_length":0,"maximum_length":null}},"default":null,"unit":""}),
+        json!({}),
+    );
+    for (input, expected) in [
+        (
+            json!({"Integer":{"minimum":null,"maximum":null}}),
+            json!({"Integer":{}}),
+        ),
+        (
+            json!({"Real":{"minimum":null,"maximum":2.5}}),
+            json!({"Real":{"maximum":2.5}}),
+        ),
+        (
+            json!({"String":{"minimum_length":4,"maximum_length":null}}),
+            json!({"String":{"minimum_length":4}}),
+        ),
+        (json!({"Record":{"supertype":null}}), json!({"Record":{}})),
+        (
+            json!({"Enumeration":{"literals":[]}}),
+            json!({"Enumeration":{"literals":[]}}),
+        ),
+    ] {
+        compact(
+            Context::Element(Kind::DataType),
+            json!({"definition":input}),
+            json!({"definition":expected}),
+        );
+    }
+    compact(
+        Context::Element(Kind::DataType),
+        json!({"definition":"Boolean","default":{"Boolean":false}}),
+        json!({"definition":"Boolean","default":{"Boolean":false}}),
+    );
+}
+
+#[test]
+fn port_contract_and_its_required_payload_stay_explicit() {
+    compact(
+        Context::Element(Kind::Port),
+        json!({"contract":"Legacy","legacy":{"direction":"Out","interface":null}}),
+        json!({"contract":"Legacy","legacy":{"direction":"Out"}}),
+    );
+    for contract in [
+        json!({"FunctionInput":{"incoming_items":[]}}),
+        json!({"FunctionOutput":{"outgoing_items":[]}}),
+        json!({"Component":{"kind":"Standard","orientation":"Unset"}}),
+    ] {
+        compact(
+            Context::Element(Kind::Port),
+            json!({"contract":contract.clone(),"legacy":null}),
+            json!({"contract":contract}),
+        );
+    }
+}
+
+#[test]
+fn occurrence_whole_default_is_distinct_from_selected_constructor_payload() {
+    compact(
+        Context::Element(Kind::Occurrence),
+        json!({"body":{"Exchange":{"exchange":null,"sender":null,"receiver":null,"message_kind":"Asynchronous","reply_to":null,"values":[]}},"precondition":"","postcondition":""}),
+        json!({}),
+    );
+    for (input, expected) in [
+        (
+            json!({"Action":{"action":null,"lifeline":null}}),
+            json!({"Action":{}}),
+        ),
+        (
+            json!({"State":{"state":null,"lifeline":null}}),
+            json!({"State":{}}),
+        ),
+        (
+            json!({"SequenceReference":{"sequence":null}}),
+            json!({"SequenceReference":{}}),
+        ),
+        (
+            json!({"ScenarioUse":{"scenario":null,"bindings":[]}}),
+            json!({"ScenarioUse":{"bindings":[]}}),
+        ),
+        (
+            json!({"Branch":{"guard":"","occurrences":[]}}),
+            json!({"Branch":{"guard":"","occurrences":[]}}),
+        ),
+        (
+            json!({"Fragment":{"operator":"Parallel","branches":[]}}),
+            json!({"Fragment":{"operator":"Parallel","branches":[]}}),
+        ),
+        (
+            json!({"Control":{"kind":"Choice"}}),
+            json!({"Control":{"kind":"Choice"}}),
+        ),
+    ] {
+        compact(
+            Context::Element(Kind::Occurrence),
+            json!({"body":input}),
+            json!({"body":expected}),
+        );
+    }
+}
+
+#[test]
+fn unresolved_operation_and_required_message_value_are_preserved() {
+    compact(
+        Context::Element(Kind::Occurrence),
+        json!({"body":{"Exchange":{"exchange":null,"sender":null,"receiver":null,"message_kind":"Asynchronous","reply_to":null,"values":[{"field":"f","path":[],"expression":""}],"operation":{"allocation":null}}}}),
+        json!({"body":{"Exchange":{"values":[{"field":"f","expression":""}],"operation":{}}}}),
+    );
+    compact(
+        Context::Element(Kind::Occurrence),
+        json!({"body":{"Exchange":{"exchange":"flow","sender":"a","receiver":"b","message_kind":{"Timer":{"expression":""}},"reply_to":"request","values":[],"operation":null}}}),
+        json!({"body":{"Exchange":{"exchange":"flow","sender":"a","receiver":"b","message_kind":{"Timer":{"expression":""}},"reply_to":"request"}}}),
+    );
+}
+
+#[test]
+fn event_body_whole_default_does_not_prune_selected_required_fields() {
+    compact(
+        Context::Element(Kind::Event),
+        json!({"body":{"Signal":{"items":[]}}}),
+        json!({}),
+    );
+    for body in [
+        json!({"Signal":{"items":["i"]}}),
+        json!({"Time":{"kind":"After","expression":""}}),
+        json!({"Change":{"expression":""}}),
+    ] {
+        compact(
+            Context::Element(Kind::Event),
+            json!({"body":body.clone()}),
+            json!({"body":body}),
+        );
+    }
+}
+
+#[test]
+fn relation_required_endpoints_and_contextual_payloads_remain() {
+    for kind in RelationKind::ALL {
+        compact(
+            Context::Relation(kind),
+            json!({"description":"","source":"s","target":"t","future":[]}),
+            json!({"source":"s","target":"t","future":[]}),
+        );
+    }
+    compact(
+        Context::Relation(RelationKind::FunctionalExchange),
+        json!({"source":"s","target":"t","source_port":"sp","target_port":"tp","items":[]}),
+        json!({"source":"s","target":"t","source_port":"sp","target_port":"tp"}),
+    );
+    let contextual = json!({"owner":"o","source":{"references":[],"occurrence":"s"},"target":{"references":[],"occurrence":"t"},"purpose":{"Precedence":{"guard":""}}});
+    compact(
+        Context::Relation(RelationKind::ContextualLink),
+        contextual.clone(),
+        contextual,
+    );
+}
+
+#[test]
+fn relation_defaults_preserve_contextual_orientation_and_multiplicity() {
+    for (kind, orientation) in [
+        (RelationKind::BoundaryExchange, true),
+        (RelationKind::CommunicationMean, false),
+    ] {
+        compact(
+            Context::Relation(kind),
+            json!({"oriented":orientation,"items":[]}),
+            json!({}),
+        );
+        compact(
+            Context::Relation(kind),
+            json!({"oriented":!orientation}),
+            json!({"oriented":!orientation}),
+        );
+    }
+    compact(
+        Context::Relation(RelationKind::DataAssociation),
+        json!({"source_role":"","target_role":"","source_minimum":0,"target_minimum":0,"source_maximum":null,"target_maximum":null,"source_navigable":false,"target_navigable":false}),
+        json!({}),
+    );
+    compact(
+        Context::Relation(RelationKind::DataAssociation),
+        json!({"source_maximum":0,"target_maximum":1,"source_navigable":true}),
+        json!({"source_maximum":0,"target_maximum":1,"source_navigable":true}),
+    );
+    compact(
+        Context::Relation(RelationKind::InterfaceItemAllocation),
+        json!({"order":0,"transmission":"Unspecified","acquisition":"Unspecified"}),
+        json!({}),
+    );
+    compact(
+        Context::Relation(RelationKind::CapabilityExtend),
+        json!({"condition":""}),
+        json!({}),
+    );
+    compact(
+        Context::Relation(RelationKind::SequenceLink),
+        json!({"guard":""}),
+        json!({}),
+    );
+    compact(
+        Context::Relation(RelationKind::StateAction),
+        json!({"phase":"Do"}),
+        json!({}),
+    );
+    compact(
+        Context::Relation(RelationKind::StateTransition),
+        json!({"transition_kind":"External","trigger":"","guard":"","effect":"","triggers":[],"effects":[]}),
+        json!({}),
+    );
+    compact(
+        Context::Relation(RelationKind::StateTransition),
+        json!({"transition_kind":"Internal","triggers":["t"],"effects":["e"]}),
+        json!({"transition_kind":"Internal","triggers":["t"],"effects":["e"]}),
+    );
+}
+
+#[test]
+fn diagram_options_remove_only_unrestricted_defaults() {
+    let defaults = json!({"hidden_edges":[],"relation_kinds":"All","work_categories":"All","participant_categories":"All","coverage":"All","work_contexts":"All","exchange_labels":"Name"});
+    compact(
+        Context::Diagram,
+        json!({"description":"","layer":"Oa","projection":"Overview","routes":[],"view_options":defaults}),
+        json!({}),
+    );
+    compact(
+        Context::Diagram,
+        json!({"layer":"Sa","projection":{"StateMachine":{"machine":"m"}},"view_options":{"hidden_edges":[],"relation_kinds":{"Only":[]},"work_categories":{"Any":[]},"participant_categories":"All","coverage":"All","work_contexts":{"Any":[]},"exchange_labels":"Name"}}),
+        json!({"layer":"Sa","projection":{"StateMachine":{"machine":"m"}},"view_options":{"relation_kinds":{"Only":[]},"work_categories":{"Any":[]},"work_contexts":{"Any":[]}}}),
+    );
+    compact(
+        Context::Diagram,
+        json!({"routes":[{"edge":"e","waypoints":[],"label":null}]}),
+        json!({"routes":[{"edge":"e"}]}),
+    );
+}
+
+#[test]
+fn node_whole_defaults_preserve_negative_zero_and_required_coordinates() {
+    compact(
+        Context::Node,
+        json!({"diagram":"d","element":"e","position":{"x":0.0,"y":0.0},"size":{"width":224.0,"height":94.0},"collapsed":false}),
+        json!({"diagram":"d","element":"e"}),
+    );
+    for position in [
+        json!({"x":-0.0,"y":0.0}),
+        json!({"x":0.0,"y":-0.0}),
+        json!({"x":1.0,"y":0.0}),
+    ] {
+        let result = rendered(
+            Context::Node,
+            &json!({"position":position.clone()}),
+            Mode::Compact,
+        );
+        assert_eq!(result, json!({"position":position.clone()}));
+        for coordinate in ["x", "y"] {
+            assert_eq!(
+                result["position"][coordinate].as_f64().unwrap().to_bits(),
+                position[coordinate].as_f64().unwrap().to_bits(),
+                "coordinate sign is part of fidelity"
+            );
+        }
+    }
+    compact(
+        Context::Node,
+        json!({"size":{"width":300.0,"height":94.0},"port_anchors":[{"port":"p","side":"Left","offset":0.0}]}),
+        json!({"size":{"width":300.0,"height":94.0},"port_anchors":[{"port":"p","side":"Left","offset":0.0}]}),
+    );
+}
+
+#[test]
+fn artifact_present_empty_strings_and_trace_history_stay_distinct() {
+    compact(
+        Context::Artifact,
+        json!({"owner":"o","description":"","relation":"References","uri":"","revision":null,"fragment":null}),
+        json!({"owner":"o"}),
+    );
+    compact(
+        Context::Artifact,
+        json!({"owner":"o","relation":"Implements","revision":"","fragment":""}),
+        json!({"owner":"o","relation":"Implements","revision":"","fragment":""}),
+    );
+    compact(
+        Context::Trace,
+        json!({"oa":"o","sa":"s","description":"","kind":"Refinement","baseline":null}),
+        json!({"oa":"o","sa":"s"}),
+    );
+    compact(
+        Context::Trace,
+        json!({"baseline":{"oa":{"name":"","description":""},"sa":{"name":"s","description":""}}}),
+        json!({"baseline":{"oa":{"name":"","description":""},"sa":{"name":"s","description":""}}}),
+    );
+    let baseline = json!({"oa":{"name":"o","description":""},"sa":{"name":"s","description":""},"semantic":{"facets":[{"Value":null},{"Value":[]},{"Value":false},{"Value":0},{"Value":""}]}});
+    compact(
+        Context::Trace,
+        json!({"kind":"Manual","baseline":baseline.clone()}),
+        json!({"kind":"Manual","baseline":baseline}),
+    );
+}
+
+#[test]
+fn nested_future_fields_prevent_whole_default_removal() {
+    // These sentinels exercise preservation, not current parser admission of
+    // unknown fields. Only known slots may lose their redundant defaults.
+    compact(
+        Context::Element(Kind::DataType),
+        json!({"definition":{"String":{"minimum_length":0,"maximum_length":null,"future":[]}}}),
+        json!({"definition":{"String":{"minimum_length":0,"future":[]}}}),
+    );
+    compact(
+        Context::Element(Kind::Occurrence),
+        json!({"body":{"Exchange":{"exchange":null,"sender":null,"receiver":null,"message_kind":"Asynchronous","reply_to":null,"values":[],"operation":null,"future":false}}}),
+        json!({"body":{"Exchange":{"future":false}}}),
+    );
+    compact(
+        Context::Diagram,
+        json!({"view_options":{"hidden_edges":[],"relation_kinds":"All","work_categories":"All","participant_categories":"All","coverage":"All","work_contexts":"All","exchange_labels":"Name","future":null}}),
+        json!({"view_options":{"future":null}}),
+    );
+}
+
+#[test]
+fn unknown_and_multikey_constructor_wrappers_are_not_reinterpreted() {
+    for definition in [
+        json!({"Future":{"minimum":null,"maximum":null}}),
+        json!({"String":{"minimum_length":0,"maximum_length":null},"Future":{}}),
+    ] {
+        compact(
+            Context::Element(Kind::DataType),
+            json!({"definition":definition.clone()}),
+            json!({"definition":definition}),
+        );
+    }
+    for body in [
+        json!({"Future":{"operation":null,"values":[]}}),
+        json!({"Exchange":{"exchange":null,"values":[]},"Future":{}}),
+    ] {
+        let fields = json!({"body":body});
+        assert_eq!(
+            rendered(
+                Context::Element(Kind::Occurrence),
+                &fields,
+                Mode::CompleteForEdit
+            ),
+            fields,
+            "do not invent a selected Exchange constructor in an unknown wrapper",
+        );
+        compact(Context::Element(Kind::Occurrence), fields.clone(), fields);
+    }
+}

crates/oa-core/src/source_files.rs

@@ -40,6 +40,7 @@ pub enum DiskExpectation {
 
 /// `bundle` retains detached and invalid buffers. Compile `reachable_bundle()`;
 /// use `diagnostics` to explain files that discovery could not read or parse.
+/// Diagnostic spans describe `bundle` bytes, including before UUID stabilization.
 /// Expectations always describe disk bytes before UUID stabilization.
 #[derive(Debug, Clone)]
 pub struct DiskProject {
@@ -526,10 +527,11 @@ pub fn discover_missing(
         result.expectations.keys().chain(result.bundle.files.keys()),
     )?;
     if result.diagnostics.is_empty() {
-        match compile_bundle(&result.reachable_bundle(), limits) {
-            Ok(compiled) => result.diagnostics = compiled.diagnostics,
-            Err(diagnostics) => result.diagnostics = diagnostics,
-        }
+        // Discovery retains raw editor bytes. Compilation may insert UUIDs or
+        // rewrite older syntax, so its returned locations belong to a different
+        // bundle. Lint still performs semantic migration and model validation;
+        // Open/Apply separately compile and install the rewritten source.
+        result.diagnostics = lint_bundle(&result.reachable_bundle(), limits);
     }
     let pending = journal_path(&result.root, &result.bundle.entry);
     if fs::symlink_metadata(&pending).is_ok() {

crates/oa-core/src/source_project.rs

@@ -726,7 +726,8 @@ fn apply_edits(bundle: &mut SourceBundle, edits: Edits) -> Result<(), Vec<Source
 pub fn format_bundle(project: &Project) -> SourceBundle {
     let ownership = default_ownership(project);
     let aliases: BTreeMap<_, _> = project.identities().into_iter().collect();
-    let mut declarations = language::format_declarations(project);
+    let mut declarations =
+        language::format_declarations(project, language::DeclarationFormat::Compact);
     declarations.sort_by_key(|(id, _)| declaration_order(project, *id, &aliases));
     let mut files: BTreeMap<LogicalPath, String> = BTreeMap::new();
     for (id, declaration) in declarations {
@@ -735,11 +736,13 @@ pub fn format_bundle(project: &Project) -> SourceBundle {
             .or_default()
             .push_str(&unindent(&declaration));
     }
-    let mut entry = format!(
-        "arcadia {SCHEMA_VERSION};\n{}{{\n    description {};\n",
-        project_header(project),
-        quote(&project.description)
-    );
+    let mut entry = format!("arcadia {SCHEMA_VERSION};\n{}{{\n", project_header(project));
+    if !project.description.is_empty() {
+        entry.push_str(&format!(
+            "    description {};\n",
+            quote(&project.description)
+        ));
+    }
     for path in files.keys() {
         entry.push_str(&format!("    include {};\n", quote(path)));
     }
@@ -850,8 +853,25 @@ pub fn update_bundle_with_identity_map(
         )]);
     }
     let origins: BTreeMap<_, _> = identities.iter().map(|(old, new)| (*new, *old)).collect();
-    let before: BTreeMap<_, _> = language::format_declarations(old).into_iter().collect();
-    let after: BTreeMap<_, _> = language::format_declarations(project).into_iter().collect();
+    // Comparison must include defaults even when persistence serialization or
+    // compact output omits them. Otherwise an unrelated payload edit erases
+    // unchanged explicit fields from the authored document.
+    let before: BTreeMap<_, _> =
+        language::format_declarations(old, language::DeclarationFormat::CompleteForEdit)
+            .into_iter()
+            .collect();
+    let after: BTreeMap<_, _> =
+        language::format_declarations(project, language::DeclarationFormat::CompleteForEdit)
+            .into_iter()
+            .collect();
+    let compact: BTreeMap<_, _> =
+        language::format_declarations(project, language::DeclarationFormat::Compact)
+            .into_iter()
+            .collect();
+    let compact_values: BTreeMap<_, _> =
+        language::format_declarations(project, language::DeclarationFormat::CompactValues)
+            .into_iter()
+            .collect();
     let old_aliases: BTreeMap<_, _> = old
         .identities()
         .into_iter()
@@ -907,6 +927,27 @@ pub fn update_bundle_with_identity_map(
             };
             let mut previous = parse(old_text)?;
             let mut next = parse(new_text)?;
+            let next_id = identities[&id];
+            let value_text = &compact_values[&next_id];
+            let insertion = InsertionSyntax::new(
+                &next.fields,
+                &parse(value_text)?.fields,
+                value_text,
+                &parse(&compact[&next_id])?.fields,
+            );
+            let old_kind = previous.header["kind"];
+            let new_kind = next.header["kind"];
+            if old_text[old_kind.start..old_kind.end] != new_text[new_kind.start..new_kind.end]
+                && let language::EditKind::Record(actual_fields) = &actual.fields.kind
+                && let language::EditKind::Record(previous_fields) = &mut previous.fields.kind
+            {
+                // An implicit value is supplied by its declaration context.
+                // After a kind change, an unchanged value may need explicit
+                // syntax (e.g. BoundaryExchange true -> CommunicationMean true).
+                // Reconsider only absent fields; authored explicit values still
+                // compare against their complete old values and keep trivia.
+                previous_fields.retain(|key, _| actual_fields.contains_key(key));
+            }
             if actual.lexical_owner.is_some()
                 && let language::EditKind::Record(fields) = &actual.fields.kind
                 && !fields.contains_key("parent")
@@ -923,6 +964,7 @@ pub fn update_bundle_with_identity_map(
                 source,
                 before: old_text,
                 after: new_text,
+                insertion: Some(&insertion),
                 old_aliases: &old_aliases,
                 new_aliases: &new_aliases,
                 legacy_value_paths: false,
@@ -930,7 +972,18 @@ pub fn update_bundle_with_identity_map(
             };
             let local = edits.entry(path.clone()).or_default();
             update.header(&actual.header, &previous.header, &next.header, local);
-            update.value(&actual.fields, Some(&previous.fields), &next.fields, local);
+            let context = if old.diagrams.contains_key(&id) {
+                EditContext::Diagram
+            } else {
+                EditContext::Other
+            };
+            update.value(
+                &actual.fields,
+                Some(&previous.fields),
+                &next.fields,
+                context,
+                local,
+            );
         }
     }
     if old.id != project.id || old.alias != project.alias || old.name != project.name {
@@ -953,6 +1006,7 @@ pub fn update_bundle_with_identity_map(
             source,
             before: &before,
             after: &after,
+            insertion: None,
             old_aliases: &old_aliases,
             new_aliases: &new_aliases,
             legacy_value_paths: false,
@@ -1011,7 +1065,7 @@ pub fn update_bundle_with_identity_map(
         project,
         identities,
         &original_order,
-        &after,
+        &compact,
         limits,
     )?;
     let result = compile_bundle(&bundle, limits)?;
@@ -1119,10 +1173,96 @@ fn inserted_value(text: &str, indent: &str, source: &str) -> String {
     output
 }
 
+// Value fragments retain required payload fields even when the enclosing
+// declaration field is itself omittable. For example, a selected String type
+// needs minimum_length; an Event Signal needs items. The complete tree remains
+// the comparison authority; this parallel tree is only an insertion template.
+struct InsertionSyntax<'a> {
+    source: &'a str,
+    values: BTreeMap<usize, Span>,
+    omitted_fields: BTreeSet<usize>,
+}
+impl<'a> InsertionSyntax<'a> {
+    fn new(
+        complete: &language::EditValue,
+        compact_values: &language::EditValue,
+        source: &'a str,
+        compact: &language::EditValue,
+    ) -> Self {
+        let mut result = Self {
+            source,
+            values: BTreeMap::new(),
+            omitted_fields: BTreeSet::new(),
+        };
+        result.collect(complete, compact_values);
+        if let (language::EditKind::Record(all), language::EditKind::Record(kept)) =
+            (&complete.kind, &compact.kind)
+        {
+            for (key, field) in all {
+                if !kept.contains_key(key) {
+                    result.omitted_fields.insert(field.value.span.start);
+                }
+            }
+        }
+        result
+    }
+    fn collect(&mut self, complete: &language::EditValue, compact: &language::EditValue) {
+        // Borrow the existing compact text once. Copying each containing record
+        // here would duplicate a large nested payload at every depth.
+        self.values.insert(complete.span.start, compact.span);
+        match (&complete.kind, &compact.kind) {
+            (language::EditKind::Record(all), language::EditKind::Record(kept)) => {
+                for (key, field) in all {
+                    if let Some(next) = kept.get(key) {
+                        self.collect(&field.value, &next.value);
+                    } else {
+                        self.omitted_fields.insert(field.value.span.start);
+                    }
+                }
+            }
+            (language::EditKind::List(all), language::EditKind::List(kept)) => {
+                assert_eq!(
+                    all.len(),
+                    kept.len(),
+                    "compaction preserves array membership"
+                );
+                for (field, next) in all.iter().zip(kept) {
+                    self.collect(field, next);
+                }
+            }
+            _ => {}
+        }
+    }
+}
+
+// Schema context is explicit: similarly named fields in arbitrary records must
+// never acquire Scenario row identity or move their authored trivia.
+#[derive(Clone, Copy)]
+enum EditContext {
+    Other,
+    Diagram,
+    Layout,
+    Scenario,
+    Lanes,
+    Messages,
+}
+impl EditContext {
+    fn field(self, name: &str) -> Self {
+        match (self, name) {
+            (Self::Diagram, "layout") => Self::Layout,
+            (Self::Layout, "Scenario") => Self::Scenario,
+            (Self::Scenario, "lanes") => Self::Lanes,
+            (Self::Scenario, "messages") => Self::Messages,
+            _ => Self::Other,
+        }
+    }
+}
+
 struct SyntaxUpdate<'a> {
     source: &'a str,
     before: &'a str,
     after: &'a str,
+    insertion: Option<&'a InsertionSyntax<'a>>,
     old_aliases: &'a BTreeMap<String, String>,
     new_aliases: &'a BTreeMap<String, String>,
     // Source3 migration only adds path qualification; the existing field identity
@@ -1131,6 +1271,16 @@ struct SyntaxUpdate<'a> {
     identity_origins: Option<&'a BTreeMap<Id, Id>>,
 }
 impl SyntaxUpdate<'_> {
+    fn inserted(&self, value: &language::EditValue) -> &str {
+        self.insertion
+            .and_then(|syntax| {
+                syntax
+                    .values
+                    .get(&value.span.start)
+                    .map(|span| &syntax.source[span.start..span.end])
+            })
+            .unwrap_or(&self.after[value.span.start..value.span.end])
+    }
     fn header(
         &self,
         actual: &BTreeMap<&str, Span>,
@@ -1185,6 +1335,7 @@ impl SyntaxUpdate<'_> {
         actual: &language::EditValue,
         before: Option<&language::EditValue>,
         after: &language::EditValue,
+        context: EditContext,
         edits: &mut LocalEdits,
     ) {
         use language::EditKind;
@@ -1200,7 +1351,7 @@ impl SyntaxUpdate<'_> {
                         None
                     }
                 });
-                self.record(actual.span, fields, previous, next, edits);
+                self.record(actual.span, fields, previous, next, context, edits);
             }
             (EditKind::List(items), EditKind::List(next)) => {
                 let previous = before.and_then(|old| {
@@ -1210,7 +1361,7 @@ impl SyntaxUpdate<'_> {
                         None
                     }
                 });
-                self.list(actual.span, items, previous, next, edits);
+                self.list(actual.span, items, previous, next, context, edits);
             }
             (EditKind::Reference(_), EditKind::Reference(alias)) => {
                 let token = significant(&self.source[actual.span.start..actual.span.end])
@@ -1243,7 +1394,7 @@ impl SyntaxUpdate<'_> {
             _ => {
                 erase_syntax(self.source, actual.span, edits);
                 let text = inserted_value(
-                    &self.after[after.span.start..after.span.end],
+                    self.inserted(after),
                     indent_at(self.source, actual.span.start),
                     self.source,
                 );
@@ -1263,6 +1414,7 @@ impl SyntaxUpdate<'_> {
         actual: &BTreeMap<String, language::EditField>,
         before: Option<&BTreeMap<String, language::EditField>>,
         after: &BTreeMap<String, language::EditField>,
+        context: EditContext,
         edits: &mut LocalEdits,
     ) {
         // A typed constructor tag change retains shared fields and their trivia.
@@ -1286,7 +1438,13 @@ impl SyntaxUpdate<'_> {
                     },
                     new_key.clone(),
                 ));
-                self.value(&field.value, Some(&old.value), &new.value, edits);
+                self.value(
+                    &field.value,
+                    Some(&old.value),
+                    &new.value,
+                    context.field(new_key),
+                    edits,
+                );
                 return;
             }
         }
@@ -1298,9 +1456,16 @@ impl SyntaxUpdate<'_> {
                         .and_then(|fields| fields.get(key))
                         .map(|field| &field.value),
                     &next.value,
+                    context.field(key),
                     edits,
                 );
-            } else {
+            } else if !(matches!(context, EditContext::Diagram)
+                && key == "layout"
+                && before.is_some_and(|fields| !fields.contains_key(key)))
+            {
+                // Canonical None omits layout. Preserve an authored explicit
+                // none while another field changes; a real Some->None clear
+                // still removes the former payload and retains its trivia.
                 erase_syntax(self.source, field.span, edits);
             }
         }
@@ -1308,6 +1473,9 @@ impl SyntaxUpdate<'_> {
             .iter()
             .filter(|(key, field)| {
                 !actual.contains_key(*key)
+                    && self.insertion.is_none_or(|syntax| {
+                        !syntax.omitted_fields.contains(&field.value.span.start)
+                    })
                     && before
                         .and_then(|fields| fields.get(*key))
                         .is_none_or(|old| !self.same(&old.value, &field.value))
@@ -1326,11 +1494,7 @@ impl SyntaxUpdate<'_> {
             .unwrap_or_else(|| format!("{}    ", indent_at(self.source, span.start)));
         let mut text = String::new();
         for (key, field) in added {
-            let value = inserted_value(
-                &self.after[field.value.span.start..field.value.span.end],
-                &indent,
-                self.source,
-            );
+            let value = inserted_value(self.inserted(&field.value), &indent, self.source);
             if multiline {
                 text.push_str(&indent);
                 text.push_str(&format!("{key} {value};{}", newline(self.source)));
@@ -1355,6 +1519,7 @@ impl SyntaxUpdate<'_> {
         actual: &[language::EditValue],
         before: Option<&[language::EditValue]>,
         after: &[language::EditValue],
+        context: EditContext,
         edits: &mut LocalEdits,
     ) {
         let previous = before.unwrap_or(&[]);
@@ -1367,6 +1532,7 @@ impl SyntaxUpdate<'_> {
                     self.old_aliases,
                     self.legacy_value_paths,
                     None,
+                    context,
                 )
             })
             .collect();
@@ -1379,6 +1545,7 @@ impl SyntaxUpdate<'_> {
                     self.new_aliases,
                     self.legacy_value_paths,
                     self.identity_origins,
+                    context,
                 )
             })
             .collect();
@@ -1407,7 +1574,7 @@ impl SyntaxUpdate<'_> {
                 .all(|(i, source)| *source == Some(i))
         {
             for (i, (current, next)) in actual.iter().zip(after).enumerate() {
-                self.value(current, previous.get(i), next, edits);
+                self.value(current, previous.get(i), next, EditContext::Other, edits);
             }
             return;
         }
@@ -1440,7 +1607,13 @@ impl SyntaxUpdate<'_> {
                 let chunk = chunks[index];
                 text.push_str(&self.source[chunk.start..current.span.start]);
                 let mut local = Vec::new();
-                self.value(current, previous.get(index), next, &mut local);
+                self.value(
+                    current,
+                    previous.get(index),
+                    next,
+                    EditContext::Other,
+                    &mut local,
+                );
                 text.push_str(&changed_text(self.source, current.span, local));
                 suffix = &self.source[current.span.end..chunk.end];
             } else {
@@ -1450,11 +1623,7 @@ impl SyntaxUpdate<'_> {
                 } else {
                     text.push(' ');
                 }
-                text.push_str(&inserted_value(
-                    &self.after[next.span.start..next.span.end],
-                    &indent,
-                    self.source,
-                ));
+                text.push_str(&inserted_value(self.inserted(next), &indent, self.source));
                 suffix = "";
             }
             if i + 1 < after.len() {
@@ -1483,14 +1652,58 @@ impl SyntaxUpdate<'_> {
     }
 }
 
+fn scenario_item_key(
+    value: &language::EditValue,
+    aliases: &BTreeMap<String, String>,
+    context: EditContext,
+) -> Option<String> {
+    use language::EditKind;
+    let EditKind::Record(fields) = &value.kind else {
+        return None;
+    };
+    let reference = |value: &language::EditValue| {
+        if let EditKind::Reference(alias) = &value.kind {
+            aliases.get(alias).cloned()
+        } else {
+            None
+        }
+    };
+    match context {
+        EditContext::Lanes => {
+            reference(&fields.get("lifeline")?.value).map(|id| format!("scenario-lane:{id}"))
+        }
+        EditContext::Messages => {
+            let EditKind::Record(address) = &fields.get("address")?.value.kind else {
+                return None;
+            };
+            let occurrence = reference(&address.get("occurrence")?.value)?;
+            let path: Vec<_> = match address.get("references") {
+                None => Vec::new(),
+                Some(field) => {
+                    let EditKind::List(path) = &field.value.kind else {
+                        return None;
+                    };
+                    path.iter().map(reference).collect::<Option<Vec<_>>>()?
+                }
+            };
+            Some(format!("scenario-message:{}:{occurrence}", path.join("/")))
+        }
+        _ => None,
+    }
+}
+
 fn item_key(
     value: &language::EditValue,
     source: &str,
     aliases: &BTreeMap<String, String>,
     legacy_value_paths: bool,
     origins: Option<&BTreeMap<Id, Id>>,
+    context: EditContext,
 ) -> Option<String> {
     use language::EditKind;
+    if matches!(context, EditContext::Lanes | EditContext::Messages) {
+        return scenario_item_key(value, aliases, context);
+    }
     if matches!(value.kind, EditKind::Record(_))
         && let Some(key) = language::semantic_row_key(
             &source[value.span.start..value.span.end],

crates/oa-core/src/source_project/source_migration.rs

@@ -11,7 +11,10 @@ pub(super) fn upgrade(
         .as_ref()
         .expect("an explicit source migration report");
     let project = &current.decoded.project;
-    let canonical: BTreeMap<_, _> = language::format_declarations(project).into_iter().collect();
+    let canonical: BTreeMap<_, _> =
+        language::format_declarations(project, language::DeclarationFormat::CompleteForEdit)
+            .into_iter()
+            .collect();
     let changed: BTreeSet<_> = report
         .semantic_defaults
         .iter()
@@ -59,6 +62,7 @@ pub(super) fn upgrade(
                 source,
                 before: source,
                 after,
+                insertion: None,
                 old_aliases: &aliases,
                 new_aliases: &aliases,
                 legacy_value_paths: true,
@@ -68,6 +72,11 @@ pub(super) fn upgrade(
                 &actual.fields,
                 Some(&actual.fields),
                 &next.fields,
+                if project.diagrams.contains_key(&id) {
+                    EditContext::Diagram
+                } else {
+                    EditContext::Other
+                },
                 edits.entry(path.clone()).or_default(),
             );
         }

crates/oa-core/src/transitions.rs

@@ -750,7 +750,7 @@ pub fn plan_transition(
                 );
                 continue;
             }
-            if !compatible_existing(project, *source, target, request.direction) {
+            if !counterpart_compatible(project, *source, target, request.direction) {
                 conflict(
                     &mut plan,
                     Some(*source),
@@ -1317,12 +1317,22 @@ fn compatible_kinds(source: Kind, target: Kind, direction: TransitionDirection)
     }
     inferred_kind(source, direction) == Some(target)
 }
-fn compatible_existing(
+/// Whether existing records have compatible layers, categories and kinds for
+/// an ordinary transition. This is candidate eligibility, not approval of a
+/// complete plan: properties, dependencies and structural conflicts still need
+/// the normal preview and apply validation. Manual traces are not restricted
+/// by this predicate.
+pub fn counterpart_compatible(
     p: &Project,
     source: Id,
     target: Id,
     direction: TransitionDirection,
 ) -> bool {
+    if p.layer_of(source) != Some(direction.source_layer())
+        || p.layer_of(target) != Some(direction.target_layer())
+    {
+        return false;
+    }
     match (p.elements.get(&source), p.elements.get(&target)) {
         (Some(a), Some(b)) => compatible_kinds(a.kind(), b.kind(), direction),
         _ => match (p.relations.get(&source), p.relations.get(&target)) {

crates/oa-core/src/validation.rs

@@ -619,6 +619,7 @@ pub fn validate(p: &Project) -> Vec<Issue> {
         }
         text(&mut out, d.id, "name", &d.name);
         text(&mut out, d.id, "description", &d.description);
+        crate::scenario_layout::validate_diagram(p, d, &mut out);
         let option_issues = if d.projection == ProjectionKind::Traceability {
             crate::view_options::validate_options_cross_layer(p, &d.view_options)
         } else {
@@ -643,6 +644,20 @@ pub fn validate(p: &Project) -> Vec<Issue> {
         }
         let mut routed_edges = BTreeSet::new();
         for (index, route) in d.routes.iter().enumerate() {
+            for attachment in [route.source_attachment, route.target_attachment]
+                .into_iter()
+                .flatten()
+            {
+                if !attachment.offset.is_finite() || !(0.0..=1.0).contains(&attachment.offset) {
+                    error(
+                        &mut out,
+                        d.id,
+                        "invalid_attachment_offset",
+                        "routes",
+                        "Connection attachment offset must be finite and between zero and one.",
+                    );
+                }
+            }
             if !routed_edges.insert(route.edge) {
                 error(
                     &mut out,

crates/oa-core/tests/attachment_geometry.rs

@@ -0,0 +1,385 @@
+use oa_core::{projection::*, routing::*, *};
+
+fn pos(x: f32, y: f32) -> Position {
+    Position { x, y }
+}
+fn anchor(side: PortAnchorSide, offset: f32) -> EdgeAttachment {
+    EdgeAttachment { side, offset }
+}
+fn fixture() -> (Project, Id, Id, Id, Id) {
+    let mut p = Project::empty();
+    let a = p
+        .add_element(Kind::Activity, Layer::Oa, "Report", None)
+        .unwrap();
+    let b = p
+        .add_element(Kind::Activity, Layer::Oa, "Receive", None)
+        .unwrap();
+    let edge = p.relate(RelationKind::Interaction, "Report status", a, b);
+    let d = p.ensure_diagram(Layer::Oa);
+    p.place(d, a, pos(50., 50.));
+    p.place(d, b, pos(750., 200.));
+    (p, d, a, b, edge)
+}
+fn stored(edge: Id) -> EdgeRoute {
+    EdgeRoute {
+        edge,
+        source_attachment: None,
+        target_attachment: None,
+        waypoints: vec![],
+        label: None,
+    }
+}
+fn routed(p: &Project, d: Id) -> RoutedView {
+    let diagram = &p.diagrams[&d];
+    route_diagram(p, diagram, &project_diagram(p, diagram))
+}
+fn near(a: f32, b: f32) {
+    assert!((a - b).abs() < 0.002, "{a} != {b}");
+}
+fn orthogonal(points: &[Position]) {
+    assert!(points.len() >= 2);
+    for span in points.windows(2) {
+        assert!(span[0].x == span[1].x || span[0].y == span[1].y, "{span:?}");
+    }
+}
+fn length(points: &[Position]) -> f32 {
+    points
+        .windows(2)
+        .map(|p| (p[0].x - p[1].x).abs() + (p[0].y - p[1].y).abs())
+        .sum()
+}
+
+#[test]
+fn authored_boundary_follows_projected_owner_and_preview_matches_committed_geometry() {
+    let (mut p, d, a, _, edge) = fixture();
+    let initial = routed(&p, d);
+    let mut route = stored(edge);
+    route.source_attachment = Some(anchor(PortAnchorSide::Bottom, 0.25));
+    route.target_attachment = Some(anchor(PortAnchorSide::Top, 0.75));
+    route.waypoints = vec![pos(460., 350.)];
+    p.diagrams.get_mut(&d).unwrap().routes.push(route.clone());
+    let view = project_diagram(&p, &p.diagrams[&d]);
+    let preview = route_edge_preview(&p, &p.diagrams[&d], &view, &initial, edge);
+    let full = routed(&p, d);
+    assert_eq!(
+        preview, full,
+        "attachment-only changes must invalidate the label-only path cache"
+    );
+    let n = view.nodes.iter().find(|n| n.element == a).unwrap();
+    assert_eq!(
+        full.edges[&edge].points[0],
+        pos(
+            n.position.x + n.size.width * 0.25,
+            n.position.y + n.size.height
+        )
+    );
+    assert_eq!(full.edges[&edge].pins, route.waypoints);
+    orthogonal(&full.edges[&edge].points);
+    let node = p
+        .diagrams
+        .get_mut(&d)
+        .unwrap()
+        .nodes
+        .values_mut()
+        .find(|n| n.element == a)
+        .unwrap();
+    node.position.x += 75.;
+    node.size.width += 100.;
+    node.size.height += 50.;
+    let moved = routed(&p, d);
+    near(
+        moved.edges[&edge].points[0].x - full.edges[&edge].points[0].x,
+        100.,
+    );
+    near(
+        moved.edges[&edge].points[0].y - full.edges[&edge].points[0].y,
+        50.,
+    );
+    assert_eq!(p.diagrams[&d].routes[0], route);
+}
+
+#[test]
+fn attachment_only_preview_cannot_reuse_old_endpoints_with_unchanged_pins() {
+    let (mut p, d, _, _, edge) = fixture();
+    let baseline = routed(&p, d);
+    let mut route = stored(edge);
+    route.source_attachment = Some(anchor(PortAnchorSide::Top, 0.2));
+    p.diagrams.get_mut(&d).unwrap().routes.push(route);
+    let view = project_diagram(&p, &p.diagrams[&d]);
+    let preview = route_edge_preview(&p, &p.diagrams[&d], &view, &baseline, edge);
+    assert_ne!(preview.edges[&edge].points, baseline.edges[&edge].points);
+    assert_eq!(preview, routed(&p, d));
+}
+
+#[test]
+fn ports_remain_authoritative_even_when_projection_filters_the_port() {
+    let mut p = Project::empty();
+    let a = p
+        .add_element(Kind::Function, Layer::Sa, "Send", None)
+        .unwrap();
+    let b = p
+        .add_element(Kind::Function, Layer::Sa, "Receive", None)
+        .unwrap();
+    let edge = p.relate(RelationKind::FunctionalExchange, "Data", a, b);
+    let d = p.ensure_diagram(Layer::Sa);
+    p.place(d, a, pos(0., 0.));
+    p.place(d, b, pos(600., 0.));
+    let diagram = p.diagrams[&d].clone();
+    let view = project_diagram(&p, &diagram);
+    let expected = route_diagram(&p, &diagram, &view);
+    assert!(semantic_port_endpoint(&p, edge, EdgeEnd::Source).is_some());
+    let mut route = stored(edge);
+    route.source_attachment = Some(anchor(PortAnchorSide::Bottom, 0.1));
+    route.target_attachment = Some(anchor(PortAnchorSide::Top, 0.9));
+    p.diagrams.get_mut(&d).unwrap().routes.push(route);
+    assert_eq!(routed(&p, d), expected);
+    let mut hidden = view.clone();
+    hidden.ports.clear();
+    for e in &mut hidden.edges {
+        e.source_port = None;
+        e.target_port = None;
+    }
+    let absent = route_diagram(&p, &diagram, &hidden);
+    assert_eq!(
+        route_diagram(&p, &p.diagrams[&d], &hidden),
+        absent,
+        "hidden ports must not activate a dormant node preference"
+    );
+}
+
+fn state(kind: Kind) -> (Project, Id, Id, Id) {
+    let mut p = Project::empty();
+    let owner = p
+        .add_element(Kind::Entity, Layer::Oa, "Crew", None)
+        .unwrap();
+    let machine = p
+        .add_element(Kind::StateMachine, Layer::Oa, "Modes", Some(owner))
+        .unwrap();
+    let region = p
+        .add_element(Kind::Region, Layer::Oa, "Main", Some(machine))
+        .unwrap();
+    let a = p.add_element(kind, Layer::Oa, "A", Some(region)).unwrap();
+    let b = p
+        .add_element(Kind::State, Layer::Oa, "B", Some(region))
+        .unwrap();
+    let edge = p.relate(RelationKind::StateTransition, "Next", a, b);
+    let d = p.ensure_diagram(Layer::Oa);
+    p.diagrams.get_mut(&d).unwrap().projection = ProjectionKind::StateMachine { machine };
+    p.place(d, a, pos(100., 100.));
+    p.place(d, b, pos(600., 100.));
+    (p, d, a, edge)
+}
+
+#[test]
+fn nonrectangular_state_attachments_intersect_the_painted_shape() {
+    for kind in [
+        Kind::Initial,
+        Kind::Junction,
+        Kind::Final,
+        Kind::Choice,
+        Kind::ShallowHistory,
+        Kind::DeepHistory,
+        Kind::EntryPoint,
+        Kind::ExitPoint,
+        Kind::Terminate,
+        Kind::Fork,
+        Kind::Join,
+        Kind::State,
+    ] {
+        let (p, d, a, _) = state(kind);
+        let diagram = &p.diagrams[&d];
+        let view = project_diagram(&p, diagram);
+        let n = view.nodes.iter().find(|n| n.element == a).unwrap();
+        for side in [
+            PortAnchorSide::Left,
+            PortAnchorSide::Right,
+            PortAnchorSide::Top,
+            PortAnchorSide::Bottom,
+        ] {
+            for offset in [0., 0.2, 0.5, 0.8, 1.] {
+                let at = attachment_point(&p, diagram, n, &anchor(side, offset));
+                let x = (at.x - n.position.x) / n.size.width;
+                let y = (at.y - n.position.y) / n.size.height;
+                match kind {
+                    Kind::Choice => near((2. * x - 1.).abs() + (2. * y - 1.).abs(), 1.),
+                    Kind::Terminate => near((x - y).abs().min((x + y - 1.).abs()), 0.),
+                    Kind::Fork | Kind::Join => near(x.min(1. - x).min(y.min(1. - y)), 0.),
+                    Kind::State => {
+                        assert!((0. ..=1.).contains(&x) && (0. ..=1.).contains(&y));
+                        if offset == 0. || offset == 1. {
+                            assert!(
+                                x != 0. && x != 1. || y != 0. && y != 1.,
+                                "rounded corner cannot use bounding-box corner"
+                            );
+                        }
+                    }
+                    _ => near((2. * x - 1.).powi(2) + (2. * y - 1.).powi(2), 1.),
+                }
+            }
+        }
+    }
+}
+
+#[test]
+fn inset_contour_leads_keep_pin_fractions_and_labels_on_the_complete_path() {
+    let (mut p, d, _, edge) = state(Kind::Choice);
+    let mut route = stored(edge);
+    route.source_attachment = Some(anchor(PortAnchorSide::Right, 0.));
+    route.waypoints = vec![pos(380., 40.)];
+    route.label = Some(EdgeLabel {
+        fraction: 0.3,
+        offset: pos(0., 0.),
+    });
+    p.diagrams.get_mut(&d).unwrap().routes.push(route);
+    let result = routed(&p, d);
+    let r = &result.edges[&edge];
+    orthogonal(&r.points);
+    assert!(r.warnings.is_empty(), "{:?}", r.warnings);
+    let pin = r.pins[0];
+    let pin_index = r.points.iter().position(|p| *p == pin).unwrap();
+    near(
+        r.pin_fractions[0],
+        length(&r.points[..=pin_index]) / length(&r.points),
+    );
+    assert_eq!(
+        r.label.anchor,
+        point_along_polyline(&r.points, 0.3).unwrap()
+    );
+}
+
+#[test]
+fn small_symbol_drag_chooses_the_intended_exit_side_at_low_zoom() {
+    for kind in [
+        Kind::Initial,
+        Kind::Choice,
+        Kind::Terminate,
+        Kind::Fork,
+        Kind::State,
+    ] {
+        let (p, d, a, _) = state(kind);
+        let view = project_diagram(&p, &p.diagrams[&d]);
+        let n = view.nodes.iter().find(|n| n.element == a).unwrap();
+        for zoom in [0.5, 1., 2.] {
+            for overshoot in [0., 20.] {
+                let cursor = pos(n.position.x + n.size.width / 2., n.position.y - overshoot);
+                let chosen =
+                    attachment_from_point(n, cursor, Some(PortAnchorSide::Right), 6. / zoom);
+                assert_eq!(
+                    chosen,
+                    anchor(PortAnchorSide::Top, 0.5),
+                    "{kind:?}, zoom {zoom}, overshoot {overshoot}"
+                );
+                let painted = attachment_point(&p, &p.diagrams[&d], n, &chosen);
+                near(painted.x, n.position.x + n.size.width / 2.);
+                near(
+                    painted.y,
+                    n.position.y
+                        + if kind == Kind::Terminate {
+                            n.size.height / 2.
+                        } else {
+                            0.
+                        },
+                );
+            }
+            let near_corner = pos(n.position.x + n.size.width - 1., n.position.y + 1.);
+            let stable =
+                attachment_from_point(n, near_corner, Some(PortAnchorSide::Right), 6. / zoom);
+            assert_eq!(
+                stable.side,
+                PortAnchorSide::Right,
+                "corner hysteresis stays stable"
+            );
+        }
+    }
+}
+
+#[test]
+fn coincident_self_attachments_retain_hard_pins_and_form_a_visible_loop() {
+    let (mut p, d, a, edge) = state(Kind::State);
+    if let RelationBody::StateTransition { target, .. } =
+        &mut p.relations.get_mut(&edge).unwrap().body
+    {
+        *target = a;
+    }
+    for pins in [vec![], vec![pos(400., 30.)]] {
+        let mut route = stored(edge);
+        route.source_attachment = Some(anchor(PortAnchorSide::Top, 0.5));
+        route.target_attachment = route.source_attachment;
+        route.waypoints = pins.clone();
+        p.diagrams.get_mut(&d).unwrap().routes = vec![route.clone()];
+        let result = routed(&p, d);
+        let r = &result.edges[&edge];
+        orthogonal(&r.points);
+        assert_eq!(r.points.first(), r.points.last());
+        assert!(length(&r.points) > 2. * PORT_STUB + 70.);
+        assert_eq!(r.pins, pins);
+        assert_eq!(r.pin_fractions.len(), pins.len());
+        assert!(
+            r.warnings.contains(&RouteWarning::CoincidentAttachments),
+            "{:?}",
+            r.warnings
+        );
+        assert_eq!(routed(&p, d), result, "deterministic fallback");
+        assert_eq!(p.diagrams[&d].routes[0], route);
+    }
+}
+
+#[test]
+fn coincident_loop_chooses_clear_side_instead_of_inventing_an_obstructed_pin() {
+    for blocker_side in [-1., 1.] {
+        let (mut p, d, a, edge) = state(Kind::State);
+        if let RelationBody::StateTransition { target, .. } =
+            &mut p.relations.get_mut(&edge).unwrap().body
+        {
+            *target = a;
+        }
+        let mut route = stored(edge);
+        route.source_attachment = Some(anchor(PortAnchorSide::Top, 0.5));
+        route.target_attachment = route.source_attachment;
+        p.diagrams.get_mut(&d).unwrap().routes.push(route);
+        let view = project_diagram(&p, &p.diagrams[&d]);
+        let source = view.nodes.iter().find(|n| n.element == a).unwrap();
+        let tip = attachment_point(
+            &p,
+            &p.diagrams[&d],
+            source,
+            &anchor(PortAnchorSide::Top, 0.5),
+        );
+        let region = p.elements[&a].parent;
+        let blocker = p
+            .add_element(Kind::State, Layer::Oa, "Detour obstruction", region)
+            .unwrap();
+        let left = if blocker_side > 0. {
+            tip.x + 30.
+        } else {
+            tip.x - 30. - 224.
+        };
+        p.place(d, blocker, pos(left, tip.y - 144.));
+        let result = routed(&p, d);
+        let r = &result.edges[&edge];
+        assert_eq!(r.warnings, vec![RouteWarning::CoincidentAttachments]);
+        orthogonal(&r.points);
+        let view = project_diagram(&p, &p.diagrams[&d]);
+        let n = view.nodes.iter().find(|n| n.element == blocker).unwrap();
+        for segment in r.points.windows(2) {
+            for step in 0..=100 {
+                let t = step as f32 / 100.;
+                let q = pos(
+                    segment[0].x + (segment[1].x - segment[0].x) * t,
+                    segment[0].y + (segment[1].y - segment[0].y) * t,
+                );
+                assert!(
+                    !(q.x > n.position.x - CLEARANCE
+                        && q.x < n.position.x + n.size.width + CLEARANCE
+                        && q.y > n.position.y - CLEARANCE
+                        && q.y < n.position.y + n.size.height + CLEARANCE),
+                    "route crosses blocker: {q:?}"
+                );
+            }
+        }
+        assert!(
+            r.pins.is_empty(),
+            "generated detours must never become authored pins"
+        );
+    }
+}

crates/oa-core/tests/attachment_lifecycle.rs

@@ -0,0 +1,272 @@
+use oa_core::{language, projection::*, routing::*, *};
+
+fn pos(x: f32, y: f32) -> Position {
+    Position { x, y }
+}
+
+fn id(project: &Project, alias: &str) -> Id {
+    project
+        .identities()
+        .into_iter()
+        .find(|(_, a)| *a == alias)
+        .unwrap()
+        .0
+}
+
+fn authored(edge: Id) -> EdgeRoute {
+    EdgeRoute {
+        edge,
+        source_attachment: Some(EdgeAttachment {
+            side: PortAnchorSide::Bottom,
+            offset: 0.2,
+        }),
+        target_attachment: Some(EdgeAttachment {
+            side: PortAnchorSide::Top,
+            offset: 0.8,
+        }),
+        waypoints: vec![pos(520., 420.)],
+        label: Some(EdgeLabel {
+            fraction: 0.35,
+            offset: pos(17., -23.),
+        }),
+    }
+}
+
+fn routed(project: &Project, diagram: Id) -> RoutedView {
+    let d = &project.diagrams[&diagram];
+    route_diagram(project, d, &project_diagram(project, d))
+}
+
+fn fixture() -> (Project, Id, Id, Id, Id, Id, Id) {
+    let mut p = language::parse(
+        r#"arcadia 7;
+project lifecycle "Attachment lifecycle" {
+ oa_activity group "Group" { oa_activity first "First" {} }
+ oa_activity second "Second" {}
+ oa_activity replacement "Replacement" {}
+ interaction signal "Signal" { source @first; target @second; }
+ diagram view "View" {}
+ diagram other "Other" {}
+}"#,
+    )
+    .unwrap();
+    let (d, other, group, first, second, replacement, edge) = (
+        id(&p, "view"),
+        id(&p, "other"),
+        id(&p, "group"),
+        id(&p, "first"),
+        id(&p, "second"),
+        id(&p, "replacement"),
+        id(&p, "signal"),
+    );
+    for diagram in [d, other] {
+        p.place(diagram, group, pos(20., 20.));
+        p.place(diagram, first, pos(100., 130.));
+        p.place(diagram, second, pos(750., 150.));
+        p.place(diagram, replacement, pos(750., 570.));
+        p.diagrams
+            .get_mut(&diagram)
+            .unwrap()
+            .routes
+            .push(authored(edge));
+    }
+    (p, d, other, group, first, replacement, edge)
+}
+
+#[test]
+fn attachment_fold_promotion_suspends_the_complete_route_and_expand_restores_it() {
+    let (mut p, d, other, group, _, _, edge) = fixture();
+    assert_eq!(semantic_port_endpoint(&p, edge, EdgeEnd::Source), None);
+    assert_eq!(semantic_port_endpoint(&p, edge, EdgeEnd::Target), None);
+    let before = p.clone();
+    let expanded = routed(&p, d);
+    let other_geometry = routed(&p, other);
+    let parent = p.diagrams[&d]
+        .nodes
+        .values()
+        .find(|n| n.element == group)
+        .unwrap()
+        .id;
+    p.diagrams
+        .get_mut(&d)
+        .unwrap()
+        .nodes
+        .get_mut(&parent)
+        .unwrap()
+        .collapsed = true;
+    let folded = routed(&p, d);
+    assert!(folded.edges[&edge].custom_suspended);
+    assert_eq!(folded.edges[&edge].pins, []);
+    assert!(
+        folded.edges[&edge]
+            .warnings
+            .contains(&RouteWarning::PromotedEndpoints)
+    );
+    assert_eq!(p.diagrams[&d].routes, before.diagrams[&d].routes);
+    let mut automatic = p.clone();
+    automatic.diagrams.get_mut(&d).unwrap().routes.clear();
+    assert_eq!(
+        folded,
+        routed(&automatic, d),
+        "attachments, pins and label must all be dormant on promotion"
+    );
+    assert_eq!(p.diagrams[&other], before.diagrams[&other]);
+    assert_eq!(routed(&p, other), other_geometry);
+    p.diagrams
+        .get_mut(&d)
+        .unwrap()
+        .nodes
+        .get_mut(&parent)
+        .unwrap()
+        .collapsed = false;
+    assert_eq!(p, before);
+    assert_eq!(routed(&p, d), expanded);
+}
+
+#[test]
+fn attachment_reconnect_retains_slot_preferences_and_other_view_records_with_exact_history() {
+    let (p, d, other, _, _, replacement, edge) = fixture();
+    let before = routed(&p, d);
+    let mut relation = p.relations[&edge].clone();
+    let RelationBody::Interaction { target, .. } = &mut relation.body else {
+        unreachable!()
+    };
+    *target = replacement;
+    let mut expected = p.clone();
+    expected.relations.insert(edge, relation.clone());
+    let mut session = Session::new(p.clone());
+    session
+        .execute(Command::EditRelation(edge, relation))
+        .unwrap();
+    assert_eq!(
+        session.project(),
+        &expected,
+        "reconnect changes only the semantic endpoint; all per-view records remain exact"
+    );
+    assert_eq!(session.project().diagrams[&other], p.diagrams[&other]);
+    for diagram in [d, other] {
+        let current = session.project();
+        let view = project_diagram(current, &current.diagrams[&diagram]);
+        let node = view
+            .nodes
+            .iter()
+            .find(|n| n.element == replacement)
+            .unwrap();
+        let preference = current.diagrams[&diagram].routes[0]
+            .target_attachment
+            .unwrap();
+        let expected_tip =
+            attachment_point(current, &current.diagrams[&diagram], node, &preference);
+        let result = routed(current, diagram);
+        assert_eq!(result.edges[&edge].points.last(), Some(&expected_tip));
+        assert_eq!(
+            result.edges[&edge].pins,
+            p.diagrams[&diagram].routes[0].waypoints
+        );
+    }
+    assert_ne!(
+        routed(session.project(), d).edges[&edge].points.last(),
+        before.edges[&edge].points.last()
+    );
+    session.undo();
+    assert_eq!(session.project(), &p);
+    assert_eq!(routed(session.project(), d), before);
+    session.redo();
+    assert_eq!(session.project(), &expected);
+}
+
+#[test]
+fn attachment_direct_port_endpoints_remain_authoritative_when_their_glyphs_are_filtered() {
+    let mut p = Project::empty();
+    let system = p
+        .add_element(Kind::System, Layer::Sa, "System", None)
+        .unwrap();
+    let actor = p
+        .add_element(Kind::SystemActor, Layer::Sa, "Actor", None)
+        .unwrap();
+    let function = p
+        .add_element(Kind::Function, Layer::Sa, "Send", None)
+        .unwrap();
+    let mut ports = Vec::new();
+    for (owner, name, contract) in [
+        (
+            system,
+            "Output",
+            PortContract::Component {
+                kind: ComponentPortKind::Flow,
+                orientation: ComponentPortOrientation::Out,
+            },
+        ),
+        (
+            actor,
+            "Input",
+            PortContract::Component {
+                kind: ComponentPortKind::Flow,
+                orientation: ComponentPortOrientation::In,
+            },
+        ),
+        (
+            function,
+            "Function output",
+            PortContract::FunctionOutput {
+                outgoing_items: vec![],
+            },
+        ),
+    ] {
+        let port = Id::new_v4();
+        p.elements
+            .insert(port, make_port(&p, port, owner, name, contract).unwrap());
+        ports.push(port);
+    }
+    p.relate(
+        RelationKind::Allocation,
+        "Function allocation",
+        system,
+        function,
+    );
+    let boundary = p.relate(
+        RelationKind::BoundaryExchange,
+        "Boundary",
+        ports[0],
+        ports[1],
+    );
+    let allocation = p.relate(
+        RelationKind::PortAllocation,
+        "Port allocation",
+        ports[0],
+        ports[2],
+    );
+    let d = p.ensure_diagram(Layer::Sa);
+    p.place(d, system, pos(0., 0.));
+    p.place(d, actor, pos(700., 0.));
+    p.place(d, function, pos(0., 450.));
+    let original = p.clone();
+    let baseline = routed(&p, d);
+    for (edge, target) in [(boundary, ports[1]), (allocation, ports[2])] {
+        assert!(baseline.edges.contains_key(&edge));
+        assert_eq!(
+            semantic_port_endpoint(&p, edge, EdgeEnd::Source),
+            Some(ports[0])
+        );
+        assert_eq!(
+            semantic_port_endpoint(&p, edge, EdgeEnd::Target),
+            Some(target)
+        );
+        let mut route = authored(edge);
+        route.waypoints.clear();
+        route.label = None;
+        p.diagrams.get_mut(&d).unwrap().routes.push(route);
+    }
+    assert_eq!(routed(&p, d), baseline);
+    let mut hidden = project_diagram(&p, &p.diagrams[&d]);
+    hidden.ports.clear();
+    for edge in &mut hidden.edges {
+        edge.source_port = None;
+        edge.target_port = None;
+    }
+    assert_eq!(
+        route_diagram(&p, &p.diagrams[&d], &hidden),
+        route_diagram(&original, &original.diagrams[&d], &hidden),
+        "filtered direct Port endpoints must not activate their stored preferences"
+    );
+}

crates/oa-core/tests/attachment_trace_ports.rs

@@ -0,0 +1,136 @@
+use oa_core::{projection::*, routing::*, *};
+
+#[test]
+fn valid_item_trace_follows_manual_port_anchors_and_ignores_dormant_attachments() {
+    let mut project = Project::empty();
+    let oa = project
+        .add_element(Kind::Activity, Layer::Oa, "Send", None)
+        .unwrap();
+    let sa = project
+        .add_element(Kind::Function, Layer::Sa, "Receive", None)
+        .unwrap();
+    let ports = [(oa, Layer::Oa), (sa, Layer::Sa)].map(|(owner, layer)| {
+        let id = Id::new_v4();
+        project.elements.insert(
+            id,
+            Element {
+                id,
+                alias: format!("port_{}", id.simple()),
+                name: "Status port".into(),
+                description: "Existing legacy port retained by Item trace".into(),
+                parent: Some(owner),
+                body: ElementBody::shared_in(
+                    layer,
+                    SharedBody::Port {
+                        contract: PortContract::Legacy,
+                        legacy: Some(LegacyPortContract {
+                            direction: PortDirection::InOut,
+                            interface: None,
+                        }),
+                    },
+                ),
+            },
+        );
+        id
+    });
+    let trace = Trace {
+        id: Id::new_v4(),
+        alias: "status_correspondence".into(),
+        name: "Status correspondence".into(),
+        description: "Preserve this semantic evidence".into(),
+        oa: ports[0],
+        sa: ports[1],
+        kind: TraceKind::Item,
+        baseline: None,
+    };
+    project.traces.insert(trace.id, trace.clone());
+    let diagram = project.ensure_diagram(Layer::Oa);
+    project.diagrams.get_mut(&diagram).unwrap().projection = ProjectionKind::Traceability;
+    let owners = [
+        project.place(diagram, oa, Position { x: 100., y: 100. }),
+        project.place(diagram, sa, Position { x: 800., y: 300. }),
+    ];
+    validate_candidate(&project).unwrap();
+    let semantic_elements = project.elements.clone();
+    let semantic_relations = project.relations.clone();
+    let semantic_traces = project.traces.clone();
+    let view = project_diagram(&project, &project.diagrams[&diagram]);
+    let edge = view.edges.iter().find(|edge| edge.id == trace.id).unwrap();
+    assert!(edge.trace);
+    assert_eq!((edge.source, edge.target), (owners[0], owners[1]));
+    assert_eq!((edge.source_port, edge.target_port), (None, None));
+    let initial = route_diagram(&project, &project.diagrams[&diagram], &view);
+    for (index, (side, offset)) in [(PortAnchorSide::Top, 0.25), (PortAnchorSide::Bottom, 0.75)]
+        .into_iter()
+        .enumerate()
+    {
+        project
+            .diagrams
+            .get_mut(&diagram)
+            .unwrap()
+            .nodes
+            .get_mut(&owners[index])
+            .unwrap()
+            .port_anchors
+            .push(PortAnchor {
+                port: ports[index],
+                side,
+                offset,
+            });
+    }
+    validate_candidate(&project).unwrap();
+    let moved_view = project_diagram(&project, &project.diagrams[&diagram]);
+    let moved = route_diagram(&project, &project.diagrams[&diagram], &moved_view);
+    for index in 0..2 {
+        let marker = moved_view
+            .ports
+            .iter()
+            .find(|port| port.element == ports[index] && port.owner == owners[index])
+            .unwrap();
+        let points = &moved.edges[&trace.id].points;
+        let tip = if index == 0 {
+            points[0]
+        } else {
+            *points.last().unwrap()
+        };
+        assert_eq!(tip, marker.position);
+        let old = &initial.edges[&trace.id].points;
+        assert_ne!(
+            tip,
+            if index == 0 {
+                old[0]
+            } else {
+                *old.last().unwrap()
+            }
+        );
+    }
+    project
+        .diagrams
+        .get_mut(&diagram)
+        .unwrap()
+        .routes
+        .push(EdgeRoute {
+            edge: trace.id,
+            waypoints: vec![],
+            label: None,
+            source_attachment: Some(EdgeAttachment {
+                side: PortAnchorSide::Bottom,
+                offset: 0.9,
+            }),
+            target_attachment: Some(EdgeAttachment {
+                side: PortAnchorSide::Top,
+                offset: 0.1,
+            }),
+        });
+    validate_candidate(&project).unwrap();
+    let dormant_view = project_diagram(&project, &project.diagrams[&diagram]);
+    assert_eq!(dormant_view, moved_view);
+    assert_eq!(
+        route_diagram(&project, &project.diagrams[&diagram], &dormant_view),
+        moved
+    );
+    assert_eq!(project.elements, semantic_elements);
+    assert_eq!(project.relations, semantic_relations);
+    assert_eq!(project.traces, semantic_traces);
+    assert_eq!(project.traces[&trace.id], trace);
+}

crates/oa-core/tests/attachment_workshop.rs

@@ -0,0 +1,154 @@
+//! Route the exact native acceptance fixture and intended saved checkpoints.
+use oa_core::{projection::project_diagram, routing::route_diagram, *};
+
+const FIXTURE: &str =
+    include_str!("../../../harness/experiments/edge-attachments-20260922/native-fixture.arcadia");
+
+fn id(project: &Project, alias: &str) -> Id {
+    project
+        .identities()
+        .into_iter()
+        .find(|(_, name)| *name == alias)
+        .unwrap()
+        .0
+}
+
+fn set(
+    project: &mut Project,
+    view: &str,
+    edge: &str,
+    end: EdgeEnd,
+    attachment: Option<(PortAnchorSide, f32)>,
+) {
+    let view = id(project, view);
+    let edge = id(project, edge);
+    let route = project
+        .diagrams
+        .get_mut(&view)
+        .unwrap()
+        .routes
+        .iter_mut()
+        .find(|route| route.edge == edge)
+        .unwrap();
+    route.set_attachment(
+        end,
+        attachment.map(|(side, offset)| EdgeAttachment { side, offset }),
+    );
+}
+
+fn clear(project: &Project, checkpoint: &str) {
+    validate_candidate(project).unwrap();
+    for (view, edges) in [
+        ("dispatch_view", &["dispatch_request"][..]),
+        ("readiness_view", &["activate", "initialize", "finish"][..]),
+    ] {
+        let diagram = &project.diagrams[&id(project, view)];
+        let routed = route_diagram(project, diagram, &project_diagram(project, diagram));
+        for alias in edges {
+            let edge = &routed.edges[&id(project, alias)];
+            assert!(
+                edge.warnings.is_empty(),
+                "{checkpoint}/{view}/{alias}: {:?}",
+                edge.warnings
+            );
+            let stored = diagram
+                .routes
+                .iter()
+                .find(|r| r.edge == id(project, alias))
+                .unwrap();
+            assert_eq!(
+                edge.pins, stored.waypoints,
+                "{checkpoint}/{alias}: manual pins retained"
+            );
+        }
+    }
+}
+
+#[test]
+fn native_workshop_baseline_and_planned_attachments_have_clear_routes() {
+    use EdgeEnd::{Source, Target};
+    use PortAnchorSide::{Bottom, Top};
+    let mut project = language::parse(FIXTURE).unwrap();
+    let baseline = project.clone();
+    clear(&project, "B");
+    set(
+        &mut project,
+        "dispatch_view",
+        "dispatch_request",
+        Source,
+        Some((Top, 0.25)),
+    );
+    clear(&project, "O1");
+    set(
+        &mut project,
+        "dispatch_view",
+        "dispatch_request",
+        Target,
+        Some((Bottom, 0.75)),
+    );
+    clear(&project, "O2");
+    set(
+        &mut project,
+        "dispatch_view",
+        "dispatch_request",
+        Source,
+        None,
+    );
+    clear(&project, "O3");
+    set(
+        &mut project,
+        "readiness_view",
+        "activate",
+        Source,
+        Some((Top, 0.25)),
+    );
+    clear(&project, "S1");
+    set(
+        &mut project,
+        "readiness_view",
+        "activate",
+        Target,
+        Some((Bottom, 0.75)),
+    );
+    clear(&project, "S2");
+    set(&mut project, "readiness_view", "activate", Target, None);
+    clear(&project, "S3");
+    set(
+        &mut project,
+        "readiness_view",
+        "initialize",
+        Source,
+        Some((Top, 0.5)),
+    );
+    clear(&project, "S4");
+    set(
+        &mut project,
+        "readiness_view",
+        "finish",
+        Source,
+        Some((Top, 0.5)),
+    );
+    clear(&project, "S5");
+    assert_eq!(project.elements, baseline.elements);
+    assert_eq!(project.relations, baseline.relations);
+    for alias in ["dispatch_reference", "readiness_reference", "ports_view"] {
+        let view = id(&project, alias);
+        assert_eq!(project.diagrams[&view], baseline.diagrams[&view]);
+    }
+    for alias in ["dispatch_view", "readiness_view"] {
+        let view = id(&project, alias);
+        assert_eq!(
+            project.diagrams[&view].nodes,
+            baseline.diagrams[&view].nodes
+        );
+        for route in &project.diagrams[&view].routes {
+            let original = baseline.diagrams[&view]
+                .routes
+                .iter()
+                .find(|r| r.edge == route.edge)
+                .unwrap();
+            assert_eq!(route.waypoints, original.waypoints);
+            assert_eq!(route.label, original.label);
+        }
+    }
+}

crates/oa-core/tests/default_omission_admission.rs

@@ -0,0 +1,344 @@
+//! Existing source-7 nested omission compatibility, independently of formatting.
+//!
+//! Selected constructors use their own field contracts. These handwritten
+//! sources and literal models distinguish nullable optional slots from required
+//! fields; they do not prescribe compact canonical output or broaden admission.
+
+use oa_core::{source_project::*, *};
+use std::collections::BTreeMap;
+
+fn id(number: u8) -> Id {
+    Id::parse_str(&format!("00000000-0000-4000-8000-{number:012}")).unwrap()
+}
+
+fn bundle(declarations: &str) -> SourceBundle {
+    let source = format!(
+        "arcadia 7;\nproject p \"Admission\" id \"00000000-0000-4000-8000-000000000001\" {{\n{declarations}\n}}\n"
+    );
+    SourceBundle {
+        entry: "project.arcadia".into(),
+        files: BTreeMap::from([("project.arcadia".into(), source)]),
+    }
+}
+
+fn element(number: u8, alias: &str, name: &str, parent: Option<Id>, body: ElementBody) -> Element {
+    Element {
+        id: id(number),
+        alias: alias.into(),
+        name: name.into(),
+        description: String::new(),
+        parent,
+        body,
+    }
+}
+
+fn assert_admitted(input: &SourceBundle, elements: Vec<Element>) -> Project {
+    let expected = Project {
+        schema_version: 7,
+        id: id(1),
+        alias: "p".into(),
+        name: "Admission".into(),
+        description: String::new(),
+        elements: elements.into_iter().map(|e| (e.id, e)).collect(),
+        relations: BTreeMap::new(),
+        diagrams: BTreeMap::new(),
+        artifact_links: BTreeMap::new(),
+        traces: BTreeMap::new(),
+    };
+    let compiled = compile_bundle(input, ProjectLimits::default()).unwrap();
+    assert_eq!(compiled.decoded.project, expected, "complete literal model");
+    assert_eq!(
+        compiled.bundle, *input,
+        "fixed IDs require no source stabilization"
+    );
+    compiled.decoded.project
+}
+
+fn prefix(layer: Layer) -> &'static str {
+    match layer {
+        Layer::Oa => "oa",
+        Layer::Sa => "sa",
+    }
+}
+
+fn data_bundle(layer: Layer, definition: &str) -> SourceBundle {
+    bundle(&format!(
+        "    {}_data_type subject \"Subject\" id \"00000000-0000-4000-8000-000000000002\" {{ definition {{ {definition}; }}; }}",
+        prefix(layer)
+    ))
+}
+
+fn admit_data(layer: Layer, source: &str, definition: DataTypeDefinition) -> Project {
+    assert_admitted(
+        &data_bundle(layer, source),
+        vec![element(
+            2,
+            "subject",
+            "Subject",
+            None,
+            ElementBody::shared_in(
+                layer,
+                SharedBody::DataType {
+                    definition,
+                    default: None,
+                    unit: String::new(),
+                },
+            ),
+        )],
+    )
+}
+
+fn assert_missing(input: &SourceBundle, field: &str) {
+    let errors = compile_bundle(input, ProjectLimits::default()).unwrap_err();
+    assert_eq!(
+        errors.len(),
+        1,
+        "expect the targeted admission error: {errors:?}"
+    );
+    let diagnostic = &errors[0].diagnostic;
+    assert_eq!(diagnostic.code, "invalid_source", "{errors:?}");
+    assert!(
+        diagnostic.message.to_lowercase().contains("missing") && diagnostic.message.contains(field),
+        "must reject the missing constructor field {field}, not an unrelated model rule: {errors:?}"
+    );
+}
+
+#[test]
+fn integer_optional_bounds_can_be_omitted_individually_and_together() {
+    for layer in [Layer::Oa, Layer::Sa] {
+        for (omitted, explicit, minimum, maximum) in [
+            (
+                "Integer {}",
+                "Integer { minimum none; maximum none; }",
+                None,
+                None,
+            ),
+            (
+                "Integer { maximum 9; }",
+                "Integer { minimum none; maximum 9; }",
+                None,
+                Some(9),
+            ),
+            (
+                "Integer { minimum -3; }",
+                "Integer { minimum -3; maximum none; }",
+                Some(-3),
+                None,
+            ),
+        ] {
+            let expected = DataTypeDefinition::Integer { minimum, maximum };
+            assert_eq!(
+                admit_data(layer, omitted, expected.clone()),
+                admit_data(layer, explicit, expected),
+                "omitted and explicit optional Integer bounds agree"
+            );
+        }
+    }
+}
+
+#[test]
+fn real_optional_bounds_can_be_omitted_individually_and_together() {
+    for layer in [Layer::Oa, Layer::Sa] {
+        for (omitted, explicit, minimum, maximum) in [
+            (
+                "Real {}",
+                "Real { minimum none; maximum none; }",
+                None,
+                None,
+            ),
+            (
+                "Real { maximum 2.5; }",
+                "Real { minimum none; maximum 2.5; }",
+                None,
+                Some(2.5),
+            ),
+            (
+                "Real { minimum -1.25; }",
+                "Real { minimum -1.25; maximum none; }",
+                Some(-1.25),
+                None,
+            ),
+        ] {
+            let expected = DataTypeDefinition::Real { minimum, maximum };
+            assert_eq!(
+                admit_data(layer, omitted, expected.clone()),
+                admit_data(layer, explicit, expected),
+                "omitted and explicit optional Real bounds agree"
+            );
+        }
+    }
+}
+
+#[test]
+fn string_optional_maximum_can_be_omitted_without_resetting_required_minimum() {
+    for layer in [Layer::Oa, Layer::Sa] {
+        let expected = DataTypeDefinition::String {
+            minimum_length: 4,
+            maximum_length: None,
+        };
+        assert_eq!(
+            admit_data(layer, "String { minimum_length 4; }", expected.clone()),
+            admit_data(
+                layer,
+                "String { minimum_length 4; maximum_length none; }",
+                expected,
+            ),
+        );
+    }
+}
+
+#[test]
+fn explicitly_selected_string_requires_minimum_even_when_whole_definition_has_a_default() {
+    for layer in [Layer::Oa, Layer::Sa] {
+        assert_missing(&data_bundle(layer, "String {}"), "minimum_length");
+        assert_missing(
+            &data_bundle(layer, "String { maximum_length none; }"),
+            "minimum_length",
+        );
+        admit_data(
+            layer,
+            "String { minimum_length 0; }",
+            DataTypeDefinition::String {
+                minimum_length: 0,
+                maximum_length: None,
+            },
+        );
+    }
+}
+
+#[test]
+fn absent_numeric_maximum_is_distinct_from_an_explicit_zero_bound() {
+    for layer in [Layer::Oa, Layer::Sa] {
+        let unbounded = admit_data(
+            layer,
+            "Integer { minimum -3; }",
+            DataTypeDefinition::Integer {
+                minimum: Some(-3),
+                maximum: None,
+            },
+        );
+        let bounded = admit_data(
+            layer,
+            "Integer { minimum -3; maximum 0; }",
+            DataTypeDefinition::Integer {
+                minimum: Some(-3),
+                maximum: Some(0),
+            },
+        );
+        assert_ne!(unbounded, bounded, "zero is a bound, not omitted syntax");
+    }
+}
+
+#[test]
+fn record_has_no_required_payload_field_and_omitted_supertype_means_none() {
+    for layer in [Layer::Oa, Layer::Sa] {
+        let expected = DataTypeDefinition::Record { supertype: None };
+        assert_eq!(
+            admit_data(layer, "Record {}", expected.clone()),
+            admit_data(layer, "Record { supertype none; }", expected),
+        );
+        let errors = compile_bundle(
+            &data_bundle(layer, "Record { fields []; }"),
+            ProjectLimits::default(),
+        )
+        .unwrap_err();
+        assert_eq!(errors.len(), 1, "{errors:?}");
+        assert_eq!(errors[0].diagnostic.code, "invalid_source", "{errors:?}");
+        assert!(
+            errors[0]
+                .diagnostic
+                .message
+                .contains("unknown field `fields`"),
+            "Record remains a closed constructor: {errors:?}"
+        );
+    }
+}
+
+#[test]
+fn enumeration_still_requires_its_list_even_when_empty_list_is_admitted() {
+    for layer in [Layer::Oa, Layer::Sa] {
+        assert_missing(&data_bundle(layer, "Enumeration {}"), "literals");
+        admit_data(
+            layer,
+            "Enumeration { literals []; }",
+            DataTypeDefinition::Enumeration { literals: vec![] },
+        );
+    }
+}
+
+fn port_bundle(layer: Layer, fields: &str) -> SourceBundle {
+    let owner_kind = match layer {
+        Layer::Oa => "oa_entity",
+        Layer::Sa => "sa_system",
+    };
+    bundle(&format!(
+        "    {owner_kind} owner \"Owner\" id \"00000000-0000-4000-8000-000000000002\" {{}}\n    {}_port subject \"Subject\" id \"00000000-0000-4000-8000-000000000003\" {{ parent @owner; {fields} }}",
+        prefix(layer)
+    ))
+}
+
+fn admit_port(layer: Layer, fields: &str) -> Project {
+    let owner_body = match layer {
+        Layer::Oa => ElementBody::Oa(OaBody::Entity),
+        Layer::Sa => ElementBody::Sa(SaBody::System),
+    };
+    assert_admitted(
+        &port_bundle(layer, fields),
+        vec![
+            element(2, "owner", "Owner", None, owner_body),
+            element(
+                3,
+                "subject",
+                "Subject",
+                Some(id(2)),
+                ElementBody::shared_in(
+                    layer,
+                    SharedBody::Port {
+                        contract: PortContract::Legacy,
+                        legacy: Some(LegacyPortContract {
+                            direction: PortDirection::Out,
+                            interface: None,
+                        }),
+                    },
+                ),
+            ),
+        ],
+    )
+}
+
+#[test]
+fn legacy_port_interface_can_be_omitted_but_preserves_direction() {
+    for layer in [Layer::Oa, Layer::Sa] {
+        assert_eq!(
+            admit_port(layer, "contract Legacy; legacy { direction Out; };"),
+            admit_port(
+                layer,
+                "contract Legacy; legacy { direction Out; interface none; };"
+            ),
+        );
+    }
+}
+
+#[test]
+fn legacy_port_direction_remains_required_inside_selected_record() {
+    for layer in [Layer::Oa, Layer::Sa] {
+        assert_missing(
+            &port_bundle(layer, "contract Legacy; legacy {};"),
+            "direction",
+        );
+        assert_missing(
+            &port_bundle(layer, "contract Legacy; legacy { interface none; };"),
+            "direction",
+        );
+    }
+}
+
+#[test]
+fn port_declaration_still_requires_explicit_contract() {
+    for layer in [Layer::Oa, Layer::Sa] {
+        assert_missing(
+            &port_bundle(layer, "legacy { direction Out; };"),
+            "contract",
+        );
+    }
+}

crates/oa-core/tests/default_omission_fidelity.rs

@@ -0,0 +1,445 @@
+//! Public flat/modular formatter fidelity over frozen input and bounded mutations.
+//! Legacy fixture migration uses the public parser. The original adapter tests
+//! and exact inputs remain archived at source commit 2a64344; this suite exercises
+//! production formatters, not that frozen experiment or lossless model edits.
+
+use oa_core::{language, source_project::*, *};
+use std::collections::BTreeMap;
+
+const COASTAL: &str = include_str!("../../../examples/coastal-rescue.arcadia");
+const KEYED: &str =
+    include_str!("../../../harness/fixtures/release1-native/semantic-keyed.arcadia");
+const STATES: &str =
+    include_str!("../../../harness/fixtures/release1-native/state-actions.arcadia");
+const DENSE: &str =
+    include_str!("../../../harness/fixtures/release1-native/dense-40/dense-40.arcadia");
+const OPERATIONS: &str = include_str!(
+    "../../../harness/fixtures/interface-operation-probe/output/boundary-only.arcadia"
+);
+
+fn read(source: &str) -> Project {
+    language::parse(source).unwrap()
+}
+
+fn identity(project: &Project, alias: &str) -> Id {
+    project
+        .identities()
+        .into_iter()
+        .find(|(_, name)| *name == alias)
+        .unwrap()
+        .0
+}
+
+fn assert_common_omissions(project: &Project, compiled: &CompiledSourceProject) {
+    if project.description.is_empty() {
+        assert!(compiled.index.project_description.is_none());
+    }
+    let descriptions = project
+        .elements
+        .values()
+        .map(|e| (e.id, &e.description))
+        .chain(project.relations.values().map(|r| (r.id, &r.description)))
+        .chain(project.diagrams.values().map(|d| (d.id, &d.description)))
+        .chain(
+            project
+                .artifact_links
+                .values()
+                .map(|a| (a.id, &a.description)),
+        )
+        .chain(project.traces.values().map(|t| (t.id, &t.description)));
+    for (id, description) in descriptions {
+        if description.is_empty() {
+            assert!(
+                !compiled
+                    .index
+                    .fields
+                    .contains_key(&(id, "description".into()))
+            );
+        }
+    }
+    for element in project.elements.values().filter(|e| e.parent.is_none()) {
+        assert!(
+            !compiled
+                .index
+                .fields
+                .contains_key(&(element.id, "parent".into()))
+        );
+    }
+}
+
+fn assert_fidelity(label: &str, project: &Project) -> (Project, String) {
+    let flat = language::format(project);
+    let compact_model = read(&flat);
+    assert_eq!(
+        compact_model, *project,
+        "{label}: every persistent field survives"
+    );
+
+    let input = SourceBundle {
+        entry: "project.arcadia".into(),
+        files: BTreeMap::from([("project.arcadia".into(), flat.clone())]),
+    };
+    let compiled = compile_bundle(&input, ProjectLimits::default()).unwrap();
+    assert_eq!(
+        compiled.decoded.project, *project,
+        "{label}: source-project compile"
+    );
+    assert_eq!(
+        compiled.bundle, input,
+        "{label}: compact identities/source are stable"
+    );
+
+    assert_common_omissions(project, &compiled);
+    assert_eq!(
+        language::format(&compact_model),
+        flat,
+        "{label}: flat idempotence"
+    );
+
+    let modular = format_bundle(project);
+    assert!(
+        modular.files.len() > 1,
+        "{label}: exercise generated includes"
+    );
+    let modular_compiled = compile_bundle(&modular, ProjectLimits::default()).unwrap();
+    assert_eq!(
+        modular_compiled.decoded.project, *project,
+        "{label}: complete modular model"
+    );
+    assert_eq!(
+        modular_compiled.bundle, modular,
+        "{label}: modular source/IDs are stable"
+    );
+    assert_common_omissions(project, &modular_compiled);
+    assert_eq!(
+        format_bundle(&compact_model),
+        modular,
+        "{label}: flat-to-modular determinism"
+    );
+    assert_eq!(
+        format_bundle(&modular_compiled.decoded.project),
+        modular,
+        "{label}: modular idempotence"
+    );
+
+    // Pinned measured compact bytes from the published fidelity-1 stderr.log at
+    // 2a64344, not a comparison against today's (now compact) canonical writer.
+    // A small header-layout allowance avoids enforcing incidental blank lines.
+    let measured_compact_bytes = match label {
+        "coastal-source3" => 28_465,
+        "keyed-source5-history" => 12_066,
+        "state-actions-source5" => 6_673,
+        "dense40-source6" => 19_342,
+        "boundary-operations-source6" => 3_660,
+        "state-negative-zero" => 6_672,
+        "keyed-present-empty-default" => 12_108,
+        "coastal-present-empty-artifact-strings" => 28_483,
+        "boundary-selected-and-unresolved-operations" => 3_806,
+        _ => panic!("missing independent compact measurement for {label}"),
+    };
+    assert!(
+        flat.len() <= measured_compact_bytes + 16,
+        "{label}: {} bytes exceeds compact evidence budget {}",
+        flat.len(),
+        measured_compact_bytes + 16
+    );
+    (compact_model, flat)
+}
+
+#[test]
+fn migrated_coastal_oa_sa_views_ports_artifacts_and_traces_roundtrip() {
+    assert!(COASTAL.starts_with("arcadia 3;"));
+    let project = read(COASTAL);
+    assert!(project.elements.values().any(|e| e.layer() == Layer::Oa));
+    assert!(project.elements.values().any(|e| e.layer() == Layer::Sa));
+    assert!(
+        project
+            .elements
+            .values()
+            .any(|e| matches!(e.shared(), Some(SharedBody::Port { .. })))
+    );
+    assert!(project.elements.values().any(
+        |e| matches!(e.shared(), Some(SharedBody::Scenario { steps, .. }) if !steps.is_empty())
+    ));
+    assert!(project.diagrams.values().any(|d| d.layer == Layer::Oa
+        && d.projection == ProjectionKind::FunctionalDataflow
+        && !d.nodes.is_empty()));
+    assert!(project.diagrams.values().any(|d| d.layer == Layer::Sa
+        && d.projection == ProjectionKind::Allocation
+        && !d.nodes.is_empty()));
+    assert!(!project.artifact_links.is_empty());
+    assert!(project.traces.values().any(|t| t.baseline.is_some()));
+    assert_fidelity("coastal-source3", &project);
+}
+
+#[test]
+fn keyed_scenarios_records_and_historical_binding_annotation_facets_roundtrip() {
+    let project = read(KEYED);
+    for layer in [Layer::Oa, Layer::Sa] {
+        assert!(project.elements.values().any(|e| e.layer() == layer
+            && matches!(
+                e.shared(),
+                Some(SharedBody::DataType {
+                    definition: DataTypeDefinition::Record { .. },
+                    ..
+                })
+            )));
+        assert!(project.elements.values().any(|e| e.layer() == layer && matches!(e.shared(), Some(SharedBody::Occurrence { body: OccurrenceBody::ScenarioUse { bindings, .. }, .. }) if !bindings.is_empty())));
+    }
+    assert!(project.elements.values().any(|e| matches!(e.shared(), Some(SharedBody::Occurrence { body: OccurrenceBody::Exchange { values, .. }, .. }) if values.iter().any(|v| !v.path.is_empty() && !v.expression.is_empty()))));
+    let facets: Vec<_> = project
+        .traces
+        .values()
+        .filter_map(|t| t.baseline.as_ref()?.semantic.as_ref())
+        .flat_map(|baseline| &baseline.facets)
+        .collect();
+    assert!(
+        facets
+            .iter()
+            .any(|facet| matches!(facet, semantic::FacetReview::Binding { .. }))
+    );
+    assert!(
+        facets
+            .iter()
+            .any(|facet| matches!(facet, semantic::FacetReview::Annotation { .. }))
+    );
+    assert!(
+        KEYED.contains("uuid \""),
+        "fixture contains historical identity atoms"
+    );
+    let (_, source) = assert_fidelity("keyed-source5-history", &project);
+    assert!(
+        source.contains("uuid \""),
+        "historical atoms remain historical"
+    );
+}
+
+#[test]
+fn state_machine_projection_typed_actions_and_bounded_integer_roundtrip() {
+    let project = read(STATES);
+    let machine = identity(&project, "operating");
+    let view = &project.diagrams[&identity(&project, "state_view")];
+    assert_eq!(view.projection, ProjectionKind::StateMachine { machine });
+    assert!(!view.nodes.is_empty());
+    for phase in [
+        StateActionKind::Entry,
+        StateActionKind::Do,
+        StateActionKind::Exit,
+    ] {
+        assert!(project.relations.values().any(|r| matches!(&r.body, RelationBody::StateAction { phase: actual, .. } if *actual == phase)));
+    }
+    assert!(project.relations.values().any(|r| matches!(&r.body, RelationBody::StateTransition { transition_kind: TransitionKind::Internal, triggers, effects, .. } if !triggers.is_empty() && !effects.is_empty())));
+    assert!(
+        matches!(project.elements[&identity(&project, "retry_budget")].shared(), Some(SharedBody::DataType { definition: DataTypeDefinition::Integer { minimum: Some(0), maximum: Some(4) }, unit, .. }) if unit == "attempts")
+    );
+    assert_fidelity("state-actions-source5", &project);
+}
+
+#[test]
+fn forty_exchange_diagram_with_categories_and_processes_roundtrip() {
+    let project = read(DENSE);
+    assert_eq!(
+        project
+            .relations
+            .values()
+            .filter(|r| r.kind() == RelationKind::Interaction)
+            .count(),
+        40
+    );
+    assert_eq!(
+        project
+            .elements
+            .values()
+            .filter(|e| e.kind() == Kind::ExchangeCategory)
+            .count(),
+        5
+    );
+    assert_eq!(
+        project
+            .elements
+            .values()
+            .filter(|e| e.kind() == Kind::Process)
+            .count(),
+        3
+    );
+    let view = &project.diagrams[&identity(&project, "forty_exchange_view")];
+    assert_eq!(view.projection, ProjectionKind::FunctionalDataflow);
+    assert_eq!(view.nodes.len(), 2);
+    assert!(view.routes.is_empty());
+    assert_eq!(
+        view.view_options.relation_kinds,
+        view_options::RelationKinds::All
+    );
+    assert_fidelity("dense40-source6", &project);
+}
+
+#[test]
+fn component_ports_interface_operations_and_boundary_calls_roundtrip() {
+    let project = read(OPERATIONS);
+    assert_eq!(
+        project
+            .relations
+            .values()
+            .filter(|r| r.kind() == RelationKind::InterfaceItemAllocation)
+            .count(),
+        2
+    );
+    assert_eq!(
+        project
+            .elements
+            .values()
+            .filter(|e| matches!(
+                e.shared(),
+                Some(SharedBody::Port {
+                    contract: PortContract::Component {
+                        kind: ComponentPortKind::Standard,
+                        ..
+                    },
+                    ..
+                })
+            ))
+            .count(),
+        2
+    );
+    assert!(project.elements.values().any(|e| matches!(
+        e.shared(),
+        Some(SharedBody::ExchangeItem {
+            mechanism: ExchangeMechanism::Operation,
+            ..
+        })
+    )));
+    assert!(project.elements.values().any(|e| matches!(e.shared(), Some(SharedBody::Scenario { viewpoint: ScenarioViewpoint::BoundaryInterface, steps, .. }) if steps.len() == 2)));
+    assert_eq!(
+        project
+            .elements
+            .values()
+            .filter(|e| matches!(
+                e.shared(),
+                Some(SharedBody::Occurrence {
+                    body: OccurrenceBody::Exchange {
+                        message_kind: MessageKind::Call,
+                        operation: None,
+                        ..
+                    },
+                    ..
+                })
+            ))
+            .count(),
+        2
+    );
+    assert_fidelity("boundary-operations-source6", &project);
+}
+
+#[test]
+fn negative_zero_node_coordinate_survives_canonical_compact_and_bundle_compile() {
+    let mut project = read(STATES);
+    let diagram = identity(&project, "state_view");
+    let node = identity(&project, "view_machine");
+    project
+        .diagrams
+        .get_mut(&diagram)
+        .unwrap()
+        .nodes
+        .get_mut(&node)
+        .unwrap()
+        .position = Position { x: -0.0, y: 0.0 };
+    let (decoded, flat) = assert_fidelity("state-negative-zero", &project);
+    let bundle = SourceBundle {
+        entry: "project.arcadia".into(),
+        files: BTreeMap::from([("project.arcadia".into(), flat)]),
+    };
+    let compiled = compile_bundle(&bundle, ProjectLimits::default()).unwrap();
+    let modular = compile_bundle(&format_bundle(&project), ProjectLimits::default()).unwrap();
+    // Project/Position PartialEq alone equates the signs of zero. Check bits in
+    // each independently decoded representation, including source-project compile.
+    for actual in [
+        &decoded,
+        &compiled.decoded.project,
+        &modular.decoded.project,
+    ] {
+        let position = &actual.diagrams[&diagram].nodes[&node].position;
+        assert_eq!(position.x.to_bits(), (-0.0_f32).to_bits());
+        assert_eq!(position.y.to_bits(), 0.0_f32.to_bits());
+    }
+}
+
+#[test]
+fn present_empty_field_default_and_unbounded_maximum_remain_distinct_from_omission() {
+    let mut project = read(KEYED);
+    let field_id = identity(&project, "oa_navigation_latitude");
+    let Some(SharedBody::DataField {
+        minimum,
+        maximum,
+        default,
+        storage,
+        ..
+    }) = project.elements.get_mut(&field_id).unwrap().shared_mut()
+    else {
+        panic!("fixture must contain the claimed DataField");
+    };
+    assert_eq!(*minimum, 0);
+    assert_eq!(*maximum, Some(1));
+    assert_eq!(*default, None);
+    assert_eq!(*storage, FieldStorage::Value);
+    *maximum = None;
+    *default = Some(vec![]);
+    let (decoded, _) = assert_fidelity("keyed-present-empty-default", &project);
+    assert!(
+        matches!(decoded.elements[&field_id].shared(), Some(SharedBody::DataField { maximum: None, default: Some(values), .. }) if values.is_empty())
+    );
+}
+
+#[test]
+fn present_empty_artifact_revision_and_fragment_survive() {
+    let mut project = read(COASTAL);
+    let artifact_id = identity(&project, "console_enclosure_cad");
+    let artifact = project.artifact_links.get_mut(&artifact_id).unwrap();
+    artifact.revision = Some(String::new());
+    artifact.fragment = Some(String::new());
+    let (decoded, _) = assert_fidelity("coastal-present-empty-artifact-strings", &project);
+    assert_eq!(
+        decoded.artifact_links[&artifact_id].revision.as_deref(),
+        Some("")
+    );
+    assert_eq!(
+        decoded.artifact_links[&artifact_id].fragment.as_deref(),
+        Some("")
+    );
+}
+
+#[test]
+fn selected_and_unresolved_operation_intent_survive_as_distinct_present_records() {
+    let mut project = read(OPERATIONS);
+    let allocation = identity(&project, "operation_probe_30");
+    assert_eq!(
+        project.relations[&allocation].kind(),
+        RelationKind::InterfaceItemAllocation
+    );
+    let selected = identity(&project, "operation_probe_43");
+    let unresolved = identity(&project, "operation_probe_44");
+    for (subject, value) in [(selected, Some(allocation)), (unresolved, None)] {
+        let Some(SharedBody::Occurrence {
+            body: OccurrenceBody::Exchange { operation, .. },
+            ..
+        }) = project.elements.get_mut(&subject).unwrap().shared_mut()
+        else {
+            panic!("fixture must contain a Call Exchange");
+        };
+        assert_eq!(*operation, None);
+        *operation = Some(OperationUse { allocation: value });
+    }
+    let (decoded, _) = assert_fidelity("boundary-selected-and-unresolved-operations", &project);
+    assert!(
+        matches!(decoded.elements[&selected].shared(), Some(SharedBody::Occurrence { body: OccurrenceBody::Exchange { operation: Some(OperationUse { allocation: Some(actual) }), .. }, .. }) if *actual == allocation)
+    );
+    assert!(matches!(
+        decoded.elements[&unresolved].shared(),
+        Some(SharedBody::Occurrence {
+            body: OccurrenceBody::Exchange {
+                operation: Some(OperationUse { allocation: None }),
+                ..
+            },
+            ..
+        })
+    ));
+}

crates/oa-core/tests/default_omission_output.rs

@@ -0,0 +1,256 @@
+//! Focused public-output contracts. Field locations come from the real compiler;
+//! token comparisons ignore layout while retaining typed tags and required syntax.
+use oa_core::{language, source_project::*, *};
+use std::collections::BTreeMap;
+
+fn project(declarations: &str) -> Project {
+    language::parse(&format!(
+        "arcadia 7; project p \"P\" id \"00000000-0000-4000-8000-000000000001\" {{ {declarations} }}"
+    )).unwrap()
+}
+
+fn exports(project: &Project) -> Vec<CompiledSourceProject> {
+    let flat = language::format(project);
+    assert_eq!(language::parse(&flat).unwrap(), *project);
+    let flat_bundle = SourceBundle {
+        entry: "project.arcadia".into(),
+        files: BTreeMap::from([("project.arcadia".into(), flat)]),
+    };
+    [flat_bundle, format_bundle(project)]
+        .into_iter()
+        .map(|bundle| {
+            let compiled = compile_bundle(&bundle, ProjectLimits::default()).unwrap();
+            assert_eq!(compiled.decoded.project, *project);
+            assert_eq!(
+                compiled.bundle, bundle,
+                "all identities are explicit and stable"
+            );
+            compiled
+        })
+        .collect()
+}
+
+fn identity(project: &Project, alias: &str) -> Id {
+    project
+        .identities()
+        .into_iter()
+        .find(|(_, name)| *name == alias)
+        .unwrap()
+        .0
+}
+
+fn field(compiled: &CompiledSourceProject, alias: &str, name: &str) -> Option<String> {
+    let location = compiled
+        .index
+        .fields
+        .get(&(identity(&compiled.decoded.project, alias), name.into()))?;
+    let text = &compiled.bundle.files[&location.path][location.span.start..location.span.end];
+    Some(
+        language::tokenize(text)
+            .into_iter()
+            .filter(|token| {
+                !matches!(
+                    token.class,
+                    language::TokenClass::Whitespace | language::TokenClass::Comment
+                )
+            })
+            .map(|token| &text[token.span.start..token.span.end])
+            .collect::<Vec<_>>()
+            .join(" "),
+    )
+}
+
+#[test]
+fn empty_project_has_no_synthetic_description_or_module() {
+    let empty = project("");
+    for compiled in exports(&empty) {
+        assert!(compiled.index.project_description.is_none());
+        assert!(compiled.index.fields.is_empty());
+        assert!(compiled.index.includes.is_empty());
+        assert_eq!(compiled.bundle.files.len(), 1);
+        assert_eq!(compiled.index.declarations.len(), 1);
+    }
+}
+
+#[test]
+fn only_empty_descriptions_disappear_whitespace_and_text_survive_exactly() {
+    let mut model =
+        project("oa_activity work \"Work\" id \"00000000-0000-4000-8000-000000000002\" {}");
+    let work = identity(&model, "work");
+    for description in ["", " \t\n", "A quoted \"requirement\" — 雨"] {
+        model.description = description.into();
+        model.elements.get_mut(&work).unwrap().description = description.into();
+        for compiled in exports(&model) {
+            assert_eq!(
+                compiled.index.project_description.is_some(),
+                !description.is_empty()
+            );
+            assert_eq!(
+                field(&compiled, "work", "description").is_some(),
+                !description.is_empty()
+            );
+            assert!(field(&compiled, "work", "parent").is_none());
+            // exports compares the complete model, including exact whitespace
+            // and escapes in both project and element descriptions.
+        }
+    }
+}
+
+#[test]
+fn sa_view_keeps_its_layer_and_node_references_but_omits_presentation_defaults() {
+    let model = project(
+        r#"
+        sa_function work "Work" id "00000000-0000-4000-8000-000000000002" {}
+        diagram view "View" id "00000000-0000-4000-8000-000000000003" { layer Sa; }
+        node placement id "00000000-0000-4000-8000-000000000004" {
+            diagram @view; element @work;
+            position { x 0.0; y 0.0; }; size { width 224.0; height 94.0; };
+            collapsed false; port_anchors [];
+        }
+    "#,
+    );
+    for compiled in exports(&model) {
+        assert_eq!(field(&compiled, "view", "layer").as_deref(), Some("Sa"));
+        for name in ["description", "projection", "routes", "view_options"] {
+            assert!(field(&compiled, "view", name).is_none(), "view.{name}");
+        }
+        assert_eq!(
+            field(&compiled, "placement", "diagram").as_deref(),
+            Some("@ view")
+        );
+        assert_eq!(
+            field(&compiled, "placement", "element").as_deref(),
+            Some("@ work")
+        );
+        for name in ["position", "size", "collapsed", "port_anchors"] {
+            assert!(
+                field(&compiled, "placement", name).is_none(),
+                "placement.{name}"
+            );
+        }
+    }
+}
+
+#[test]
+fn nested_type_defaults_disappear_without_losing_required_or_present_empty_values() {
+    let model = project(
+        r#"
+        sa_data_type implicit "Implicit" id "00000000-0000-4000-8000-000000000002" {}
+        sa_data_type integer "Integer" id "00000000-0000-4000-8000-000000000003" {
+            definition { Integer { minimum none; maximum none; }; };
+        }
+        sa_data_type text "Text" id "00000000-0000-4000-8000-000000000004" {
+            definition { String { minimum_length 4; maximum_length none; }; };
+        }
+        sa_data_type record "Record" id "00000000-0000-4000-8000-000000000005" {
+            definition { Record { supertype none; }; };
+        }
+        sa_data_type flag "Flag" id "00000000-0000-4000-8000-000000000006" {
+            definition Boolean; default { Boolean false; };
+        }
+        sa_data_field optional "Optional" id "00000000-0000-4000-8000-000000000007" {
+            parent @record; minimum 0; maximum none; default [];
+        }
+    "#,
+    );
+    for compiled in exports(&model) {
+        assert!(field(&compiled, "implicit", "definition").is_none());
+        assert_eq!(
+            field(&compiled, "integer", "definition").as_deref(),
+            Some("{ Integer { } ; }")
+        );
+        assert_eq!(
+            field(&compiled, "text", "definition").as_deref(),
+            Some("{ String { minimum_length 4 ; } ; }")
+        );
+        assert_eq!(
+            field(&compiled, "record", "definition").as_deref(),
+            Some("{ Record { } ; }")
+        );
+        assert_eq!(
+            field(&compiled, "flag", "definition").as_deref(),
+            Some("Boolean")
+        );
+        assert_eq!(
+            field(&compiled, "flag", "default").as_deref(),
+            Some("{ Boolean false ; }")
+        );
+        assert_eq!(
+            field(&compiled, "optional", "minimum").as_deref(),
+            Some("0")
+        );
+        assert_eq!(
+            field(&compiled, "optional", "maximum").as_deref(),
+            Some("none")
+        );
+        assert_eq!(
+            field(&compiled, "optional", "default").as_deref(),
+            Some("[ ]")
+        );
+        assert!(field(&compiled, "optional", "type_ref").is_none());
+    }
+}
+
+#[test]
+fn required_port_contract_and_empty_item_list_survive_while_optional_interface_disappears() {
+    let model = project(
+        r#"
+        sa_function work "Work" id "00000000-0000-4000-8000-000000000002" {}
+        sa_port sink "Sink" id "00000000-0000-4000-8000-000000000003" {
+            parent @work; contract { FunctionInput { incoming_items []; }; };
+        }
+        sa_system host "Host" id "00000000-0000-4000-8000-000000000004" {}
+        sa_port preserved "Preserved" id "00000000-0000-4000-8000-000000000005" {
+            parent @host; contract Legacy; legacy { direction Out; interface none; };
+        }
+    "#,
+    );
+    for compiled in exports(&model) {
+        assert_eq!(
+            field(&compiled, "sink", "contract").as_deref(),
+            Some("{ FunctionInput { incoming_items [ ] ; } ; }")
+        );
+        assert!(field(&compiled, "sink", "legacy").is_none());
+        assert_eq!(
+            field(&compiled, "preserved", "contract").as_deref(),
+            Some("Legacy")
+        );
+        assert_eq!(
+            field(&compiled, "preserved", "legacy").as_deref(),
+            Some("{ direction Out ; }")
+        );
+    }
+}
+
+#[test]
+fn source_scenario_default_and_selected_occurrence_constructor_remain_distinct() {
+    let model = project(
+        r#"
+        sa_scenario mixed "Mixed" id "00000000-0000-4000-8000-000000000002" { viewpoint MixedLegacy; }
+        sa_scenario strict "Strict" id "00000000-0000-4000-8000-000000000003" { viewpoint Functional; }
+        oa_process flow "Flow" id "00000000-0000-4000-8000-000000000004" { steps [@exchange, @action]; }
+        oa_occurrence exchange "Exchange" id "00000000-0000-4000-8000-000000000005" {
+            parent @flow; body { Exchange {}; };
+        }
+        oa_occurrence action "Action" id "00000000-0000-4000-8000-000000000006" {
+            parent @flow; body { Action { action none; lifeline none; }; };
+        }
+    "#,
+    );
+    for compiled in exports(&model) {
+        assert!(field(&compiled, "mixed", "viewpoint").is_none());
+        assert_eq!(
+            field(&compiled, "strict", "viewpoint").as_deref(),
+            Some("Functional")
+        );
+        assert!(field(&compiled, "exchange", "body").is_none());
+        assert_eq!(
+            field(&compiled, "action", "body").as_deref(),
+            Some("{ Action { } ; }")
+        );
+        assert_eq!(
+            field(&compiled, "action", "parent").as_deref(),
+            Some("@ flow")
+        );
+    }
+}

crates/oa-core/tests/default_omission_preservation.rs

@@ -0,0 +1,613 @@
+//! Exact-source regressions for fields skipped by persistence serialization.
+//!
+//! The archived Windows baseline confirmed three exact-source failures after
+//! full model equality passed. Complete comparison now preserves these fields;
+//! the former ignored witnesses are normal regression tests.
+//! No-op and same-record header controls remain normal tests: they must preserve
+//! the same fixtures without entering the changed-payload record-erasure branch.
+
+use oa_core::{source_project::*, *};
+use std::collections::BTreeMap;
+
+const EXCHANGE_SOURCE: &str = r#"arcadia 7;
+project p "Preservation" id "00000000-0000-4000-8000-000000000001" {
+    oa_activity first "First" id "00000000-0000-4000-8000-000000000002" {}
+    oa_activity second "Second" id "00000000-0000-4000-8000-000000000003" {}
+    interaction flow "Flow" id "00000000-0000-4000-8000-000000000004" {
+        source @first; target @second;
+    }
+    oa_process owner "Owner" id "00000000-0000-4000-8000-000000000005" {
+        steps [@subject];
+    }
+    oa_occurrence subject "Subject" id "00000000-0000-4000-8000-000000000006" {
+        parent @owner;
+        body { Exchange {
+            exchange none;
+            sender none; receiver none;
+            message_kind Asynchronous; reply_to none; values [];
+            operation   none ; // Keep this authored default and its spelling.
+        }; };
+    }
+}
+"#;
+
+const NODE_SOURCE: &str = r#"arcadia 7;
+project p "Preservation" id "00000000-0000-4000-8000-000000000001" {
+    oa_activity work "Work" id "00000000-0000-4000-8000-000000000002" {}
+    diagram view "View" id "00000000-0000-4000-8000-000000000003" {}
+    node placement id "00000000-0000-4000-8000-000000000004" {
+        diagram @view; element @work;
+        position { x 12.5; y -4.0; };
+        port_anchors   [] ; // Keep explicit automatic placement.
+    }
+}
+"#;
+
+const TRACE_SOURCE: &str = r#"arcadia 7;
+project p "Preservation" id "00000000-0000-4000-8000-000000000001" {
+    oa_activity work "Work" id "00000000-0000-4000-8000-000000000002" {}
+    sa_function function "Function" id "00000000-0000-4000-8000-000000000003" {}
+    trace mapping "Mapping" id "00000000-0000-4000-8000-000000000004" {
+        oa @work; sa @function; kind Manual;
+        baseline {
+            oa { name "Work"; description "Old OA snapshot"; };
+            sa { name "Function"; description "Old SA snapshot"; };
+            semantic   none ; // Keep the explicit prose-only baseline.
+        };
+    }
+}
+"#;
+
+const CONSTRUCTOR_SOURCE: &str = r#"arcadia 7;
+project p "Preservation" id "00000000-0000-4000-8000-000000000001" {
+    oa_scenario owner "Owner" id "00000000-0000-4000-8000-000000000002" {
+        steps [@subject];
+    }
+    oa_occurrence subject "Subject" id "00000000-0000-4000-8000-000000000003" {
+        parent @owner;
+        body { Action {
+            action none;
+            lifeline   none ; // Keep this shared field's distinctive spelling.
+        }; };
+    }
+}
+"#;
+
+const RELATION_CONTEXT_SOURCE: &str = r#"arcadia 7;
+project p "Preservation" id "00000000-0000-4000-8000-000000000001" {
+    oa_entity first "First" id "00000000-0000-4000-8000-000000000002" {}
+    oa_entity second "Second" id "00000000-0000-4000-8000-000000000003" {}
+    // These port declarations are untouched by the relation context change.
+    oa_port output "Output" id "00000000-0000-4000-8000-000000000005" {
+        parent @first; contract Legacy;
+        legacy { direction Out; interface none; };
+    }
+    oa_port input "Input" id "00000000-0000-4000-8000-000000000006" {
+        parent @second; contract Legacy;
+        legacy { direction In; interface none; };
+    }
+    boundary_exchange link "Link" id "00000000-0000-4000-8000-000000000004" {
+        source @output; target @input;
+        oriented   true ; // Retain this rationale when changing the default value.
+        items [];
+    }
+}
+"#;
+
+fn id(number: u8) -> Id {
+    Id::parse_str(&format!("00000000-0000-4000-8000-{number:012}")).unwrap()
+}
+
+fn source_bundle(source: &str) -> SourceBundle {
+    SourceBundle {
+        entry: "project.arcadia".into(),
+        files: BTreeMap::from([("project.arcadia".into(), source.into())]),
+    }
+}
+
+fn project() -> Project {
+    Project {
+        schema_version: 7,
+        id: id(1),
+        alias: "p".into(),
+        name: "Preservation".into(),
+        description: String::new(),
+        elements: BTreeMap::new(),
+        relations: BTreeMap::new(),
+        diagrams: BTreeMap::new(),
+        artifact_links: BTreeMap::new(),
+        traces: BTreeMap::new(),
+    }
+}
+
+fn element(number: u8, alias: &str, name: &str, parent: Option<Id>, body: ElementBody) -> Element {
+    Element {
+        id: id(number),
+        alias: alias.into(),
+        name: name.into(),
+        description: String::new(),
+        parent,
+        body,
+    }
+}
+
+// Handwritten typed expectations are independent of canonical serialization and
+// source hydration. No model factories or generated/random identities are used.
+fn exchange_project() -> Project {
+    let mut expected = project();
+    expected.elements = [
+        element(2, "first", "First", None, ElementBody::Oa(OaBody::Activity)),
+        element(
+            3,
+            "second",
+            "Second",
+            None,
+            ElementBody::Oa(OaBody::Activity),
+        ),
+        element(
+            5,
+            "owner",
+            "Owner",
+            None,
+            ElementBody::Oa(OaBody::Process { steps: vec![id(6)] }),
+        ),
+        element(
+            6,
+            "subject",
+            "Subject",
+            Some(id(5)),
+            ElementBody::Oa(OaBody::Shared(SharedBody::Occurrence {
+                body: OccurrenceBody::Exchange {
+                    exchange: None,
+                    sender: None,
+                    receiver: None,
+                    message_kind: MessageKind::Asynchronous,
+                    reply_to: None,
+                    values: vec![],
+                    operation: None,
+                },
+                precondition: String::new(),
+                postcondition: String::new(),
+            })),
+        ),
+    ]
+    .into_iter()
+    .map(|element| (element.id, element))
+    .collect();
+    expected.relations.insert(
+        id(4),
+        Relation {
+            id: id(4),
+            alias: "flow".into(),
+            name: "Flow".into(),
+            description: String::new(),
+            body: RelationBody::Interaction {
+                source: id(2),
+                target: id(3),
+                items: vec![],
+            },
+        },
+    );
+    expected
+}
+
+fn node_project() -> Project {
+    let mut expected = project();
+    expected.elements.insert(
+        id(2),
+        element(2, "work", "Work", None, ElementBody::Oa(OaBody::Activity)),
+    );
+    expected.diagrams.insert(
+        id(3),
+        Diagram {
+            id: id(3),
+            alias: "view".into(),
+            name: "View".into(),
+            description: String::new(),
+            layer: Layer::Oa,
+            projection: ProjectionKind::Overview,
+            view_options: view_options::ViewOptions {
+                hidden_edges: vec![],
+                relation_kinds: view_options::RelationKinds::All,
+                work_categories: view_options::CategorySelection::All,
+                participant_categories: view_options::CategorySelection::All,
+                coverage: view_options::Coverage::All,
+                work_contexts: view_options::ContextSelection::All,
+                exchange_labels: view_options::ExchangeLabels::Name,
+            },
+            nodes: BTreeMap::from([(
+                id(4),
+                NodePlacement {
+                    id: id(4),
+                    alias: "placement".into(),
+                    element: id(2),
+                    position: Position { x: 12.5, y: -4.0 },
+                    size: Size {
+                        width: 224.0,
+                        height: 94.0,
+                    },
+                    collapsed: false,
+                    port_anchors: vec![],
+                },
+            )]),
+            routes: vec![],
+            layout: None,
+        },
+    );
+    expected
+}
+
+fn trace_project() -> Project {
+    let mut expected = project();
+    expected.elements = [
+        element(2, "work", "Work", None, ElementBody::Oa(OaBody::Activity)),
+        element(
+            3,
+            "function",
+            "Function",
+            None,
+            ElementBody::Sa(SaBody::Function),
+        ),
+    ]
+    .into_iter()
+    .map(|element| (element.id, element))
+    .collect();
+    expected.traces.insert(
+        id(4),
+        Trace {
+            id: id(4),
+            alias: "mapping".into(),
+            name: "Mapping".into(),
+            description: String::new(),
+            oa: id(2),
+            sa: id(3),
+            kind: TraceKind::Manual,
+            baseline: Some(TraceBaseline {
+                oa: TracedProperties {
+                    name: "Work".into(),
+                    description: "Old OA snapshot".into(),
+                },
+                sa: TracedProperties {
+                    name: "Function".into(),
+                    description: "Old SA snapshot".into(),
+                },
+                semantic: None,
+            }),
+        },
+    );
+    expected
+}
+
+fn checked_fixture(source: &str, expected: &Project) -> CompiledSourceProject {
+    let input = source_bundle(source);
+    let compiled = compile_bundle(&input, ProjectLimits::default()).unwrap();
+    assert_eq!(
+        compiled.decoded.project, *expected,
+        "fixture model admission"
+    );
+    assert_eq!(
+        compiled.bundle, input,
+        "fixed IDs must avoid stabilization edits"
+    );
+    compiled
+}
+
+fn replacement(source: &str, before: &str, after: &str) -> String {
+    assert_eq!(
+        source.matches(before).count(),
+        1,
+        "unique authored edit token"
+    );
+    source.replacen(before, after, 1)
+}
+
+fn assert_preserved_update(
+    original: &CompiledSourceProject,
+    expected: &Project,
+    expected_source: &str,
+) {
+    // Independently admit the exact expected spelling before testing the updater.
+    let expected_bundle = source_bundle(expected_source);
+    let authored = compile_bundle(&expected_bundle, ProjectLimits::default()).unwrap();
+    assert_eq!(
+        authored.decoded.project, *expected,
+        "expected source/model agree"
+    );
+    assert_eq!(
+        authored.bundle, expected_bundle,
+        "expected source is already stable"
+    );
+
+    let updated = update_bundle(original, expected, ProjectLimits::default()).unwrap();
+    assert_eq!(
+        updated.decoded.project, *expected,
+        "entire intended model survives"
+    );
+    assert_eq!(
+        updated.bundle, expected_bundle,
+        "only the requested token may change; preserve explicit defaults and all trivia"
+    );
+}
+
+// Context changes may introduce/remove redundant default syntax. Admit each
+// narrowly enumerated spelling against the same literal target model, and then
+// compare complete source bundles. No normalization may mask edits to unrelated
+// fields, declarations, whitespace, or comments.
+fn assert_context_update(
+    original: &CompiledSourceProject,
+    expected: &Project,
+    allowed_sources: &[String],
+) {
+    let allowed: Vec<_> = allowed_sources
+        .iter()
+        .map(|source| {
+            let bundle = source_bundle(source);
+            let authored = compile_bundle(&bundle, ProjectLimits::default()).unwrap();
+            assert_eq!(
+                authored.decoded.project, *expected,
+                "allowed source/model agree"
+            );
+            assert_eq!(authored.bundle, bundle, "allowed source is already stable");
+            bundle
+        })
+        .collect();
+    let updated = update_bundle(original, expected, ProjectLimits::default()).unwrap();
+    assert_eq!(
+        updated.decoded.project, *expected,
+        "entire context-change model survives"
+    );
+    assert!(
+        allowed.contains(&updated.bundle),
+        "preserve unchanged source exactly; only listed changed/default syntax alternatives are allowed\nactual: {:?}\nallowed: {:?}",
+        updated.bundle,
+        allowed
+    );
+}
+
+#[test]
+fn explicit_exchange_operation_none_survives_noop() {
+    let expected = exchange_project();
+    let original = checked_fixture(EXCHANGE_SOURCE, &expected);
+    assert_preserved_update(&original, &expected, EXCHANGE_SOURCE);
+}
+
+#[test]
+fn explicit_exchange_operation_none_survives_header_rename() {
+    let mut expected = exchange_project();
+    let original = checked_fixture(EXCHANGE_SOURCE, &expected);
+    expected.elements.get_mut(&id(6)).unwrap().name = "Renamed subject".into();
+    let source = replacement(EXCHANGE_SOURCE, "\"Subject\"", "\"Renamed subject\"");
+    assert_preserved_update(&original, &expected, &source);
+}
+
+#[test]
+fn explicit_exchange_operation_none_survives_exchange_binding_edit() {
+    let mut expected = exchange_project();
+    let original = checked_fixture(EXCHANGE_SOURCE, &expected);
+    let Some(SharedBody::Occurrence {
+        body: OccurrenceBody::Exchange { exchange, .. },
+        ..
+    }) = expected.elements.get_mut(&id(6)).unwrap().body.shared_mut()
+    else {
+        panic!("literal fixture must be an Exchange occurrence");
+    };
+    *exchange = Some(id(4));
+    let source = replacement(EXCHANGE_SOURCE, "exchange none;", "exchange @flow;");
+    assert_preserved_update(&original, &expected, &source);
+}
+
+#[test]
+fn explicit_node_empty_port_anchors_survive_noop() {
+    let expected = node_project();
+    let original = checked_fixture(NODE_SOURCE, &expected);
+    assert_preserved_update(&original, &expected, NODE_SOURCE);
+}
+
+#[test]
+fn explicit_node_empty_port_anchors_survive_header_alias_rename() {
+    let mut expected = node_project();
+    let original = checked_fixture(NODE_SOURCE, &expected);
+    // Nodes have no display-name header. Rename the same node's header alias.
+    expected
+        .diagrams
+        .get_mut(&id(3))
+        .unwrap()
+        .nodes
+        .get_mut(&id(4))
+        .unwrap()
+        .alias = "renamed_placement".into();
+    let source = replacement(
+        NODE_SOURCE,
+        "node placement id",
+        "node renamed_placement id",
+    );
+    assert_preserved_update(&original, &expected, &source);
+}
+
+#[test]
+fn explicit_node_empty_port_anchors_survive_position_edit() {
+    let mut expected = node_project();
+    let original = checked_fixture(NODE_SOURCE, &expected);
+    expected
+        .diagrams
+        .get_mut(&id(3))
+        .unwrap()
+        .nodes
+        .get_mut(&id(4))
+        .unwrap()
+        .position
+        .x = 25.0;
+    let source = replacement(NODE_SOURCE, "x 12.5;", "x 25.0;");
+    assert_preserved_update(&original, &expected, &source);
+}
+
+#[test]
+fn explicit_trace_semantic_none_survives_noop() {
+    let expected = trace_project();
+    let original = checked_fixture(TRACE_SOURCE, &expected);
+    assert_preserved_update(&original, &expected, TRACE_SOURCE);
+}
+
+#[test]
+fn explicit_trace_semantic_none_survives_header_rename() {
+    let mut expected = trace_project();
+    let original = checked_fixture(TRACE_SOURCE, &expected);
+    expected.traces.get_mut(&id(4)).unwrap().name = "Renamed mapping".into();
+    let source = replacement(TRACE_SOURCE, "\"Mapping\"", "\"Renamed mapping\"");
+    assert_preserved_update(&original, &expected, &source);
+}
+
+#[test]
+fn explicit_trace_semantic_none_survives_snapshot_prose_edit() {
+    let mut expected = trace_project();
+    let original = checked_fixture(TRACE_SOURCE, &expected);
+    expected
+        .traces
+        .get_mut(&id(4))
+        .unwrap()
+        .baseline
+        .as_mut()
+        .unwrap()
+        .oa
+        .description = "Revised OA snapshot".into();
+    let source = replacement(
+        TRACE_SOURCE,
+        "\"Old OA snapshot\"",
+        "\"Revised OA snapshot\"",
+    );
+    assert_preserved_update(&original, &expected, &source);
+}
+
+#[test]
+fn constructor_change_removes_inapplicable_default_and_keeps_shared_default() {
+    let mut expected = project();
+    expected.elements = [
+        element(
+            2,
+            "owner",
+            "Owner",
+            None,
+            ElementBody::Oa(OaBody::Shared(SharedBody::Scenario {
+                viewpoint: ScenarioViewpoint::MixedLegacy,
+                context: None,
+                precondition: String::new(),
+                postcondition: String::new(),
+                steps: vec![id(3)],
+            })),
+        ),
+        element(
+            3,
+            "subject",
+            "Subject",
+            Some(id(2)),
+            ElementBody::Oa(OaBody::Shared(SharedBody::Occurrence {
+                body: OccurrenceBody::Action {
+                    action: None,
+                    lifeline: None,
+                },
+                precondition: String::new(),
+                postcondition: String::new(),
+            })),
+        ),
+    ]
+    .into_iter()
+    .map(|element| (element.id, element))
+    .collect();
+    let original = checked_fixture(CONSTRUCTOR_SOURCE, &expected);
+    expected.elements.get_mut(&id(3)).unwrap().body =
+        ElementBody::Oa(OaBody::Shared(SharedBody::Occurrence {
+            body: OccurrenceBody::State {
+                state: None,
+                lifeline: None,
+            },
+            precondition: String::new(),
+            postcondition: String::new(),
+        }));
+    // Remove only the inapplicable field's syntax: its separating space and all
+    // surrounding trivia stay. The shared lifeline spelling/comment is exact.
+    let source = replacement(CONSTRUCTOR_SOURCE, "body { Action {", "body { State {");
+    let compact = replacement(&source, "action none;", " ");
+    let expanded = replacement(
+        &compact,
+        "        }; };",
+        "            state none;\n        }; };",
+    );
+    // Omission of newly applicable state and explicit state none both mean the
+    // literal State target; neither may retain the old action field.
+    assert_context_update(&original, &expected, &[compact, expanded]);
+}
+
+#[test]
+fn relation_kind_change_updates_explicit_value_when_context_default_changes() {
+    let mut expected = project();
+    expected.elements = [
+        element(2, "first", "First", None, ElementBody::Oa(OaBody::Entity)),
+        element(3, "second", "Second", None, ElementBody::Oa(OaBody::Entity)),
+        element(
+            5,
+            "output",
+            "Output",
+            Some(id(2)),
+            ElementBody::Oa(OaBody::Shared(SharedBody::Port {
+                contract: PortContract::Legacy,
+                legacy: Some(LegacyPortContract {
+                    direction: PortDirection::Out,
+                    interface: None,
+                }),
+            })),
+        ),
+        element(
+            6,
+            "input",
+            "Input",
+            Some(id(3)),
+            ElementBody::Oa(OaBody::Shared(SharedBody::Port {
+                contract: PortContract::Legacy,
+                legacy: Some(LegacyPortContract {
+                    direction: PortDirection::In,
+                    interface: None,
+                }),
+            })),
+        ),
+    ]
+    .into_iter()
+    .map(|element| (element.id, element))
+    .collect();
+    expected.relations.insert(
+        id(4),
+        Relation {
+            id: id(4),
+            alias: "link".into(),
+            name: "Link".into(),
+            description: String::new(),
+            body: RelationBody::BoundaryExchange {
+                source: id(5),
+                target: id(6),
+                oriented: true,
+                items: vec![],
+            },
+        },
+    );
+    let original = checked_fixture(RELATION_CONTEXT_SOURCE, &expected);
+    // BoundaryExchange connects participant ports; CommunicationMean connects
+    // their OA entity owners. Endpoint changes are explicit parts of this target,
+    // not inferred or normalized away. Port records remain exactly unchanged.
+    expected.relations.get_mut(&id(4)).unwrap().body = RelationBody::CommunicationMean {
+        source: id(2),
+        target: id(3),
+        oriented: false,
+        items: vec![],
+    };
+    let source = replacement(
+        RELATION_CONTEXT_SOURCE,
+        "boundary_exchange link",
+        "communication_mean link",
+    );
+    let source = replacement(&source, "source @output;", "source @first;");
+    let source = replacement(&source, "target @input;", "target @second;");
+    let explicit = replacement(&source, "oriented   true ;", "oriented   false ;");
+    // Three spaces between name/value plus one before the semicolon survive
+    // syntax removal. The following rationale comment and all other bytes stay.
+    let omitted = replacement(&source, "oriented   true ;", "    ");
+    assert_context_update(&original, &expected, &[explicit, omitted]);
+}

crates/oa-core/tests/default_omission_updates.rs

@@ -0,0 +1,222 @@
+//! Public update witnesses for compact insertion and complete comparison.
+use oa_core::{language, source_project::*, *};
+use std::collections::BTreeMap;
+
+fn compile(body: &str) -> CompiledSourceProject {
+    compile_bundle(
+        &SourceBundle {
+            entry: "project.arcadia".into(),
+            files: BTreeMap::from([
+                (
+                    "project.arcadia".into(),
+                    "arcadia 7; project p \"P\" { include \"model.arcadia\"; }".into(),
+                ),
+                ("model.arcadia".into(), body.into()),
+            ]),
+        },
+        ProjectLimits::default(),
+    )
+    .unwrap()
+}
+fn id(project: &Project, alias: &str) -> Id {
+    project
+        .identities()
+        .into_iter()
+        .find(|(_, a)| *a == alias)
+        .unwrap()
+        .0
+}
+fn update(before: &CompiledSourceProject, project: &Project) -> CompiledSourceProject {
+    let result = update_bundle(before, project, ProjectLimits::default()).unwrap();
+    assert_eq!(result.decoded.project, *project);
+    assert_eq!(
+        result.bundle.files["project.arcadia"],
+        before.bundle.files["project.arcadia"]
+    );
+    assert_eq!(
+        compile_bundle(&result.bundle, ProjectLimits::default())
+            .unwrap()
+            .bundle,
+        result.bundle
+    );
+    assert_eq!(
+        update_bundle(&result, project, ProjectLimits::default())
+            .unwrap()
+            .bundle,
+        result.bundle
+    );
+    result
+}
+fn words(text: &str) -> Vec<&str> {
+    language::tokenize(text)
+        .into_iter()
+        .filter(|t| {
+            !matches!(
+                t.class,
+                language::TokenClass::Whitespace | language::TokenClass::Comment
+            )
+        })
+        .map(|t| &text[t.span.start..t.span.end])
+        .collect()
+}
+
+#[test]
+fn omitted_exchange_body_changes_to_one_compact_action_constructor() {
+    let before = compile(
+        "oa_scenario s \"S\" { steps [@o]; }\noa_occurrence o \"O\" { parent @s; // keep this\n}\n",
+    );
+    let mut project = before.decoded.project.clone();
+    let occurrence = id(&project, "o");
+    let Some(SharedBody::Occurrence { body, .. }) =
+        project.elements.get_mut(&occurrence).unwrap().shared_mut()
+    else {
+        panic!("occurrence")
+    };
+    assert!(matches!(body, OccurrenceBody::Exchange { .. }));
+    *body = OccurrenceBody::Action {
+        action: None,
+        lifeline: None,
+    };
+    let result = update(&before, &project);
+    let text = &result.bundle.files["model.arcadia"];
+    let tokens = words(text);
+    assert_eq!(tokens.iter().filter(|&&t| t == "body").count(), 1);
+    assert!(tokens.contains(&"Action"));
+    for absent in ["Exchange", "action", "lifeline", "operation", "description"] {
+        assert!(!tokens.contains(&absent), "{absent}: {text}");
+    }
+    assert!(text.contains("parent @s; // keep this"));
+}
+
+#[test]
+fn default_signal_constructor_still_inserts_its_required_empty_items() {
+    let before =
+        compile("oa_event e \"E\" { body { Time { expression \"1 s\"; kind After; }; }; }\n");
+    let mut project = before.decoded.project.clone();
+    let event = id(&project, "e");
+    let Some(SharedBody::Event { body }) = project.elements.get_mut(&event).unwrap().shared_mut()
+    else {
+        panic!("event")
+    };
+    *body = EventBody::Signal { items: vec![] };
+    let result = update(&before, &project);
+    let tokens = words(&result.bundle.files["model.arcadia"]);
+    assert!(tokens.contains(&"Signal"));
+    assert!(tokens.windows(4).any(|w| w == ["items", "[", "]", ";"]));
+    assert!(!tokens.contains(&"expression"));
+    assert!(!tokens.contains(&"kind"));
+}
+
+#[test]
+fn scalar_to_default_string_record_retains_required_minimum_only() {
+    let before = compile("oa_data_type t \"T\" { definition Boolean; // typed rationale\n}\n");
+    let mut project = before.decoded.project.clone();
+    let datatype = id(&project, "t");
+    let Some(SharedBody::DataType { definition, .. }) =
+        project.elements.get_mut(&datatype).unwrap().shared_mut()
+    else {
+        panic!("data type")
+    };
+    *definition = DataTypeDefinition::String {
+        minimum_length: 0,
+        maximum_length: None,
+    };
+    let result = update(&before, &project);
+    let text = &result.bundle.files["model.arcadia"];
+    let tokens = words(text);
+    assert!(tokens.contains(&"String"));
+    assert!(tokens.windows(3).any(|w| w == ["minimum_length", "0", ";"]));
+    assert!(!tokens.contains(&"maximum_length"));
+    assert!(text.contains("// typed rationale"));
+}
+
+#[test]
+fn inserted_route_list_item_omits_only_optional_fields() {
+    let before = compile(
+        "oa_activity a \"A\" {}\noa_activity b \"B\" {}\ninteraction flow \"Flow\" { source @a; target @b; }\ndiagram d \"D\" { routes []; // routing rationale\n}\n",
+    );
+    let mut project = before.decoded.project.clone();
+    let diagram = id(&project, "d");
+    let edge = id(&project, "flow");
+    // Deserialize only the explicit witness value, independently of omission policy.
+    project.diagrams.get_mut(&diagram).unwrap().routes =
+        serde_json::from_value(serde_json::json!([{"edge":edge,"waypoints":[],"label":null}]))
+            .unwrap();
+    let result = update(&before, &project);
+    let text = &result.bundle.files["model.arcadia"];
+    let tokens = words(text);
+    assert!(tokens.windows(4).any(|w| w == ["edge", "@", "flow", ";"]));
+    assert!(!tokens.contains(&"waypoints"));
+    assert!(!tokens.contains(&"label"));
+    assert!(text.contains("// routing rationale"));
+}
+
+#[test]
+fn zero_sign_change_inserts_position_without_default_siblings() {
+    let before = compile(
+        "oa_activity a \"A\" {}\ndiagram d \"D\" {}\nnode n { diagram @d; element @a; // placement rationale\n}\n",
+    );
+    let mut project = before.decoded.project.clone();
+    let diagram = id(&project, "d");
+    let node = id(&project, "n");
+    assert_eq!(
+        project.diagrams[&diagram].nodes[&node].position.x.to_bits(),
+        0.0_f32.to_bits()
+    );
+    project
+        .diagrams
+        .get_mut(&diagram)
+        .unwrap()
+        .nodes
+        .get_mut(&node)
+        .unwrap()
+        .position
+        .x = -0.0;
+    let result = update(&before, &project);
+    assert_eq!(
+        result.decoded.project.diagrams[&diagram].nodes[&node]
+            .position
+            .x
+            .to_bits(),
+        (-0.0_f32).to_bits()
+    );
+    let text = &result.bundle.files["model.arcadia"];
+    let tokens = words(text);
+    assert!(tokens.windows(3).any(|w| w == ["x", "-0.0", ";"]));
+    for absent in ["size", "collapsed", "port_anchors"] {
+        assert!(!tokens.contains(&absent));
+    }
+    assert!(text.contains("// placement rationale"));
+}
+
+#[test]
+fn kind_change_materializes_unchanged_value_when_its_old_omission_default_changes() {
+    let before = compile(
+        "oa_entity a \"A\" {}\noa_entity b \"B\" {}\noa_port out \"Out\" { parent @a; contract Legacy; legacy { direction Out; }; }\noa_port input \"In\" { parent @b; contract Legacy; legacy { direction In; }; }\nboundary_exchange flow \"Flow\" { source @out; target @input; // orientation inherited\n}\n",
+    );
+    let mut project = before.decoded.project.clone();
+    let flow = id(&project, "flow");
+    assert!(matches!(
+        project.relations[&flow].body,
+        RelationBody::BoundaryExchange { oriented: true, .. }
+    ));
+    project.relations.get_mut(&flow).unwrap().body = RelationBody::CommunicationMean {
+        source: id(&before.decoded.project, "a"),
+        target: id(&before.decoded.project, "b"),
+        oriented: true,
+        items: vec![],
+    };
+    let result = update(&before, &project);
+    let text = &result.bundle.files["model.arcadia"];
+    assert!(
+        words(text)
+            .windows(3)
+            .any(|w| w == ["oriented", "true", ";"])
+    );
+    assert!(text.contains("// orientation inherited"));
+    let before_ports = &before.bundle.files["model.arcadia"];
+    assert_eq!(
+        text.split("communication_mean").next().unwrap(),
+        before_ports.split("boundary_exchange").next().unwrap()
+    );
+}

crates/oa-core/tests/edge_attachments.rs

@@ -0,0 +1,290 @@
+use oa_core::{language, persistence, source_project::*, *};
+use serde_json::{Value, json};
+use std::collections::BTreeMap;
+
+const SOURCE: &str = r#"arcadia 7;
+project attachments "Connection ends" id "70000000-0000-4000-8000-000000000001" {
+ oa_activity first "First" id "70000000-0000-4000-8000-000000000002" {}
+ oa_activity second "Second" id "70000000-0000-4000-8000-000000000003" {}
+ interaction signal "Signal" id "70000000-0000-4000-8000-000000000004" { source @first; target @second; }
+ diagram view "View" id "70000000-0000-4000-8000-000000000005" {
+  routes [{ edge @signal; waypoints [{ x 120; y 80; }];
+   label { fraction 0.5; offset { x 3; y -7; }; };
+   source_attachment { side Left; offset 0.25; };
+   target_attachment { side Bottom; offset 1; };
+  }];
+ }
+ diagram other "Other" id "70000000-0000-4000-8000-000000000006" { routes [{ edge @signal; }]; }
+}
+"#;
+
+fn id(project: &Project, alias: &str) -> Id {
+    project
+        .identities()
+        .into_iter()
+        .find(|(_, a)| *a == alias)
+        .unwrap()
+        .0
+}
+
+fn original() -> Project {
+    language::parse(SOURCE).unwrap()
+}
+
+fn set(diagram: Id, route: EdgeRoute) -> Command {
+    Command::SetEdgeRoute { diagram, route }
+}
+
+#[test]
+fn edge_attachments_roundtrip_source_json_bundle_and_automatic_defaults() {
+    let project = original();
+    let view = id(&project, "view");
+    let route = &project.diagrams[&view].routes[0];
+    assert_eq!(
+        route.source_attachment,
+        Some(EdgeAttachment {
+            side: PortAnchorSide::Left,
+            offset: 0.25
+        })
+    );
+    assert_eq!(
+        route.target_attachment,
+        Some(EdgeAttachment {
+            side: PortAnchorSide::Bottom,
+            offset: 1.0
+        })
+    );
+    for text in [SOURCE.to_owned(), language::format(&project)] {
+        assert_eq!(language::parse(&text).unwrap(), project);
+    }
+    assert_eq!(
+        persistence::decode(&serde_json::to_vec(&project).unwrap()).unwrap(),
+        project
+    );
+    assert_eq!(
+        compile_bundle(&format_bundle(&project), ProjectLimits::default())
+            .unwrap()
+            .decoded
+            .project,
+        project
+    );
+
+    let automatic = &project.diagrams[&id(&project, "other")].routes[0];
+    assert_eq!(automatic.source_attachment, None);
+    assert_eq!(automatic.target_attachment, None);
+    let encoded = serde_json::to_value(automatic).unwrap();
+    assert!(encoded.get("source_attachment").is_none());
+    assert!(encoded.get("target_attachment").is_none());
+    let mut with_null = encoded.clone();
+    with_null["source_attachment"] = Value::Null;
+    with_null["target_attachment"] = Value::Null;
+    assert_eq!(
+        serde_json::from_value::<EdgeRoute>(with_null).unwrap(),
+        *automatic
+    );
+    assert_eq!(
+        serde_json::from_value::<EdgeRoute>(encoded).unwrap(),
+        *automatic
+    );
+
+    // Old source without either new field still means automatic presentation.
+    let old = SOURCE
+        .replace("   source_attachment { side Left; offset 0.25; };\n", "")
+        .replace("   target_attachment { side Bottom; offset 1; };\n", "");
+    let old = language::parse(&old).unwrap();
+    assert!(
+        old.diagrams
+            .values()
+            .flat_map(|d| &d.routes)
+            .all(|r| r.source_attachment.is_none() && r.target_attachment.is_none())
+    );
+    assert!(!language::format(&old).contains("_attachment"));
+    assert_eq!(
+        persistence::decode(&serde_json::to_vec(&old).unwrap()).unwrap(),
+        old
+    );
+}
+
+#[test]
+fn edge_attachments_reject_malformed_nested_source_and_json_without_defaults() {
+    let project = original();
+    let edge = id(&project, "signal");
+    for bad in [
+        json!({}),
+        json!({"side":"Top"}),
+        json!({"offset":0.5}),
+        json!({"side":"Diagonal","offset":0.5}),
+        json!({"side":"Top","offset":null}),
+        json!({"side":"Top","offset":0.5,"unknown":true}),
+        json!({"side":"Top","offset":"NaN"}),
+    ] {
+        for field in ["source_attachment", "target_attachment"] {
+            let mut route = json!({"edge":edge});
+            route[field] = bad.clone();
+            assert!(
+                serde_json::from_value::<EdgeRoute>(route).is_err(),
+                "{field}: {bad}"
+            );
+        }
+    }
+    for bad in [
+        "{}",
+        "{ side Top; }",
+        "{ offset 0.5; }",
+        "{ side Diagonal; offset 0.5; }",
+        "{ side Top; offset null; }",
+        "{ side Top; offset 0.5; unknown true; }",
+        "{ side Top; offset -0.01; }",
+        "{ side Top; offset 1.01; }",
+        "{ side Top; offset NaN; }",
+        "{ side Top; offset 1e999; }",
+    ] {
+        let source = SOURCE.replace("{ side Left; offset 0.25; }", bad);
+        assert!(language::parse(&source).is_err(), "{bad}");
+        let bundle = SourceBundle {
+            entry: "p.arcadia".into(),
+            files: BTreeMap::from([("p.arcadia".into(), source)]),
+        };
+        assert!(
+            compile_bundle(&bundle, ProjectLimits::default()).is_err(),
+            "{bad}"
+        );
+    }
+    for version in [1, 2] {
+        let legacy =
+            format!("arcadia {version}; project p \"P\" {{ diagram v \"V\" {{ routes []; }} }}");
+        assert!(
+            language::parse(&legacy).is_err(),
+            "legacy route extension must not be silently admitted"
+        );
+    }
+}
+
+#[test]
+fn edge_attachments_nonfinite_and_out_of_range_commands_reject_atomically() {
+    let project = original();
+    let view = id(&project, "view");
+    let first = id(&project, "first");
+    for offset in [f32::NAN, f32::INFINITY, f32::NEG_INFINITY, -0.01, 1.01] {
+        for end in [EdgeEnd::Source, EdgeEnd::Target] {
+            let mut route = project.diagrams[&view].routes[0].clone();
+            route.set_attachment(
+                end,
+                Some(EdgeAttachment {
+                    side: PortAnchorSide::Top,
+                    offset,
+                }),
+            );
+            let mut session = Session::new(project.clone());
+            assert!(
+                session
+                    .execute(Command::Batch(vec![
+                        Command::Rename(first, "Must roll back".into()),
+                        set(view, route)
+                    ]))
+                    .is_err()
+            );
+            assert_eq!(session.project(), &project);
+            assert!(!session.can_undo() && !session.can_redo());
+        }
+    }
+    for offset in [-0.01, 1.01] {
+        let mut value = serde_json::to_value(&project).unwrap();
+        value["diagrams"][view.to_string()]["routes"][0]["source_attachment"]["offset"] =
+            json!(offset);
+        assert!(persistence::decode(&serde_json::to_vec(&value).unwrap()).is_err());
+    }
+}
+
+#[test]
+fn edge_attachments_reset_one_end_and_all_routing_have_exact_history_and_view_scope() {
+    let project = original();
+    let view = id(&project, "view");
+    let edge = id(&project, "signal");
+    let mut session = Session::new(project.clone());
+    let mut route = project.diagrams[&view].routes[0].clone();
+    route.source_attachment = Some(EdgeAttachment {
+        side: PortAnchorSide::Right,
+        offset: 0.75,
+    });
+    let command = set(view, route.clone());
+    assert_eq!(
+        serde_json::from_value::<Command>(serde_json::to_value(&command).unwrap()).unwrap(),
+        command
+    );
+    session.execute(command).unwrap();
+    let mut expected = project.clone();
+    expected.diagrams.get_mut(&view).unwrap().routes[0] = route.clone();
+    assert_eq!(
+        session.project(),
+        &expected,
+        "only this view/end changes; semantic fields and other view stay exact"
+    );
+    session.undo();
+    assert_eq!(session.project(), &project);
+    assert!(!session.can_undo() && session.can_redo());
+    session.redo();
+    assert_eq!(session.project(), &expected);
+    route.source_attachment = None;
+    session.execute(set(view, route.clone())).unwrap();
+    let mut reset = expected.clone();
+    reset.diagrams.get_mut(&view).unwrap().routes[0] = route;
+    assert_eq!(
+        session.project(),
+        &reset,
+        "opposite attachment, pins and label survive endpoint reset"
+    );
+    session.undo();
+    assert_eq!(session.project(), &expected);
+    session
+        .execute(Command::RemoveEdgeRoute {
+            diagram: view,
+            edge,
+        })
+        .unwrap();
+    let mut removed = expected.clone();
+    removed.diagrams.get_mut(&view).unwrap().routes.clear();
+    assert_eq!(session.project(), &removed);
+    session.undo();
+    assert_eq!(session.project(), &expected);
+}
+
+#[test]
+fn edge_attachments_nested_writeback_preserves_comments_adjacent_tokens_and_other_files() {
+    let current = compile_bundle(&SourceBundle {
+        entry: "p.arcadia".into(),
+        files: BTreeMap::from([
+            ("p.arcadia".into(), "// project rationale\narcadia 7; project p \"P\" { include \"model.arcadia\"; include \"views.arcadia\"; }\n".into()),
+            ("model.arcadia".into(), "// untouched semantic ownership\noa_activity a \"A\" {}\noa_activity b \"B\" {}\ninteraction signal \"Signal\" { source @a; target @b; }\n".into()),
+            ("views.arcadia".into(), "// view rationale\r\ndiagram view \"View\" {\r\n routes [ { edge @signal; // endpoint explanation\r\n source_attachment { side Left; offset  0.25 ; // exact nested rationale\r\n }; target_attachment { side Bottom; offset 1; };\r\n waypoints [{ x 120; y 80; }]; label { fraction 0.5; offset { x 3; y -7; }; }; } ];\r\n}\r\ndiagram other \"Other\" { routes [{ edge @signal; }]; } // adjacent view\r\n".into()),
+        ]),
+    }, ProjectLimits::default()).unwrap();
+    let mut project = current.decoded.project.clone();
+    let view = id(&project, "view");
+    project.diagrams.get_mut(&view).unwrap().routes[0]
+        .source_attachment
+        .as_mut()
+        .unwrap()
+        .offset = 0.375;
+    let changed = update_bundle(&current, &project, ProjectLimits::default()).unwrap();
+    assert_eq!(changed.decoded.project, project);
+    for path in ["p.arcadia", "model.arcadia"] {
+        assert_eq!(changed.bundle.files[path], current.bundle.files[path]);
+    }
+    assert_eq!(
+        changed.bundle.files["views.arcadia"],
+        current.bundle.files["views.arcadia"].replace("offset  0.25 ;", "offset  0.375 ;")
+    );
+    assert_eq!(
+        compile_bundle(&changed.bundle, ProjectLimits::default())
+            .unwrap()
+            .bundle,
+        changed.bundle
+    );
+    assert_eq!(
+        update_bundle(&changed, &project, ProjectLimits::default())
+            .unwrap()
+            .bundle,
+        changed.bundle
+    );
+}

crates/oa-core/tests/language.rs

@@ -3,6 +3,16 @@ use oa_core::{language, persistence, validation, *};
 fn read(source: &str) -> Project {
     language::parse(source).unwrap_or_else(|e| panic!("{e:?}\n{source}"))
 }
+fn replace_once(source: &str, before: &str, after: &str) -> String {
+    assert_eq!(
+        source.matches(before).count(),
+        1,
+        "unique mutation anchor {before:?}"
+    );
+    let changed = source.replacen(before, after, 1);
+    assert_ne!(changed, source, "test mutation must change the source");
+    changed
+}
 fn rejected(source: &str, fragment: &str) {
     let errors = language::parse(source).expect_err(source);
     assert!(
@@ -753,8 +763,8 @@ fn typed_events_vertices_and_transition_kinds_round_trip_in_both_layers() {
         source.push('}');
         let model = read(&source);
         let canonical = language::format(&model);
+        assert!(!canonical.contains("transition_kind External;"));
         for fragment in [
-            "transition_kind External;",
             "transition_kind Local;",
             "transition_kind Internal;",
             "triggers [@deadline, @assess];",
@@ -776,6 +786,7 @@ fn typed_events_vertices_and_transition_kinds_round_trip_in_both_layers() {
             .find(|r| r.alias == "recover")
             .unwrap();
         let RelationBody::StateTransition {
+            transition_kind,
             trigger,
             guard,
             effect,
@@ -784,32 +795,42 @@ fn typed_events_vertices_and_transition_kinds_round_trip_in_both_layers() {
         else {
             panic!("expected transition")
         };
+        assert_eq!(*transition_kind, TransitionKind::External);
         assert_eq!(trigger, "Operator confirms\nНе запускать код");
         assert_eq!(guard, "available && status == \"Ready\"");
         assert_eq!(effect, "Record the assessment");
+        // External is omitted in compact output. Insert an explicit invalid
+        // discriminator into Recover using its unique, nondefault trigger list.
+        let invalid_kind = replace_once(
+            &canonical,
+            "triggers [@deadline, @assess];",
+            "transition_kind Unsupported;\n        triggers [@deadline, @assess];",
+        );
+        rejected(&invalid_kind, "Unsupported");
         for invalid in [
-            canonical.replace("transition_kind External;", "transition_kind Unsupported;"),
-            canonical.replace(
+            replace_once(
+                &canonical,
                 "triggers [@deadline, @assess];",
                 "triggers [\"deadline\", @assess];",
             ),
-            canonical.replace(
+            replace_once(
+                &canonical,
                 "triggers [@deadline, @assess];",
                 "triggers [@deadline, @deadline];",
             ),
-            canonical.replace("effects [@assess];", "effects [@payload];"),
-            canonical.replace("kind After;", "kind Relative;"),
-            canonical.replace("items [@payload];", "items [@assess];"),
+            replace_once(&canonical, "effects [@assess];", "effects [@payload];"),
+            replace_once(&canonical, "kind After;", "kind Relative;"),
+            replace_once(&canonical, "items [@payload];", "items [@assess];"),
         ] {
             assert!(
                 language::parse(&invalid).is_err(),
                 "invalid typed state/event source accepted"
             );
         }
-        let legacy = canonical
-            .replace("transition_kind External;", "")
-            .replace("triggers [@deadline, @assess];", "")
-            .replace("effects [@assess];", "");
+        // Canonical source already omits External. Removing the supplied lists
+        // independently exercises their empty omission defaults and retained prose.
+        let legacy = replace_once(&canonical, "triggers [@deadline, @assess];", "");
+        let legacy = replace_once(&legacy, "effects [@assess];", "");
         let legacy = read(&legacy);
         let RelationBody::StateTransition {
             transition_kind,
@@ -829,7 +850,7 @@ fn typed_events_vertices_and_transition_kinds_round_trip_in_both_layers() {
             (retained_trigger, retained_guard, retained_effect),
             (trigger, guard, effect)
         );
-        let draft = canonical.replace("expression \"30 s\";", "expression \"\";");
+        let draft = replace_once(&canonical, "expression \"30 s\";", "expression \"\";");
         assert!(language::parse(&draft).is_ok());
         let deadline = model
             .elements
@@ -1038,7 +1059,7 @@ fn original_v2_text_and_json_preserve_identity_and_mixed_scenarios_after_extensi
         "fixture must cover actual old scenario content"
     );
     let canonical = language::format(&from_source);
-    assert!(canonical.contains("viewpoint MixedLegacy;"));
+    assert!(!canonical.contains("viewpoint MixedLegacy;"));
     for relation in from_source.relations.values() {
         if let RelationBody::StateTransition {
             transition_kind,

crates/oa-core/tests/port_anchors.rs

@@ -441,6 +441,8 @@ fn nested_owner_bounds_group_movement_and_authored_routes_share_the_same_geometr
             diagram: d,
             route: EdgeRoute {
                 edge,
+                source_attachment: None,
+                target_attachment: None,
                 waypoints: vec![pos(500., 420.)],
                 label: None,
             },
@@ -767,7 +769,15 @@ fn resetting_last_source_anchors_preserves_comments_and_can_add_a_new_manual_rec
     assert_eq!(cleared.decoded.project, prepared.project);
     let text = &cleared.bundle.files["project.arcadia"];
     assert!(text.contains("// first rationale") && text.contains("// second rationale"));
-    assert!(!text.contains("port_anchors"));
+    // Lossless editing may retain the authored empty field and its annotations.
+    // Canonical export, rather than a model update, normalizes default syntax.
+    assert!(!language::format(&cleared.decoded.project).contains("port_anchors"));
+    assert_eq!(
+        update_bundle(&cleared, &cleared.decoded.project, ProjectLimits::default())
+            .unwrap()
+            .bundle,
+        cleared.bundle
+    );
     let prepared = prepare_command(
         &cleared.decoded.project,
         &Command::SetPortAnchor {

crates/oa-core/tests/release_routing.rs

@@ -41,6 +41,7 @@ fn fixture() -> Fixture {
             projection: ProjectionKind::Overview,
             view_options: Default::default(),
             nodes: BTreeMap::new(),
+            layout: None,
             routes: vec![],
         },
     );
@@ -70,6 +71,8 @@ fn fixture() -> Fixture {
 fn route(edge: Id) -> EdgeRoute {
     EdgeRoute {
         edge,
+        source_attachment: None,
+        target_attachment: None,
         waypoints: vec![Position { x: 550., y: 240. }, Position { x: 550., y: 360. }],
         label: Some(EdgeLabel {
             fraction: 0.4,
@@ -689,6 +692,8 @@ fn old_models_get_empty_routes_and_route_json_is_strict() {
         serde_json::from_value::<EdgeRoute>(minimal).unwrap(),
         EdgeRoute {
             edge: f.edge,
+            source_attachment: None,
+            target_attachment: None,
             waypoints: vec![],
             label: None
         }

crates/oa-core/tests/routing_geometry.rs

@@ -27,6 +27,8 @@ fn route(p: &Project, d: Id) -> RoutedView {
 fn set_route(p: &mut Project, d: Id, edge: Id, pins: Vec<Position>, label: Option<EdgeLabel>) {
     p.diagrams.get_mut(&d).unwrap().routes.push(EdgeRoute {
         edge,
+        source_attachment: None,
+        target_attachment: None,
         waypoints: pins,
         label,
     });

crates/oa-core/tests/routing_labels.rs

@@ -117,6 +117,8 @@ fn authored_overlap_is_exact_and_reset_only_repositions_automatic_text() {
         .routes
         .push(EdgeRoute {
             edge: fe,
+            source_attachment: None,
+            target_attachment: None,
             waypoints: vec![],
             label: Some(authored.clone()),
         });

crates/oa-core/tests/source7_contract.rs

@@ -261,7 +261,7 @@ fn source7_context_lifecycle_source_history_and_closed_admission() {
     assert_eq!(session.project(), &after);
     let fresh = Id::new_v4();
     let mut reidentified = after.clone();
-    references::remap_references(&mut reidentified, f.r1, fresh);
+    references::remap_references(&mut reidentified, f.r1, fresh).unwrap();
     let mut e = reidentified.elements.remove(&f.r1).unwrap();
     e.id = fresh;
     reidentified.elements.insert(fresh, e);

crates/oa-core/tests/source_files.rs

@@ -383,3 +383,87 @@ fn atomic_save_preserves_existing_unix_permissions() {
         0o640
     );
 }
+
+#[test]
+fn discovery_diagnostics_keep_raw_no_uuid_spans() {
+    let directory = setup();
+    let path = directory.path().join("parts/a.arcadia");
+    let raw =
+        "// Unicode: 航海\nsa_function first \"First\" {}\nsa_function second \"Second\" {}\n";
+    fs::write(&path, raw).unwrap();
+    let disk = load_project(
+        &directory.path().join("project.arcadia"),
+        ProjectLimits::default(),
+    )
+    .unwrap();
+    assert_eq!(disk.bundle.files["parts/a.arcadia"], raw);
+    let issue = disk
+        .diagnostics
+        .iter()
+        .find(|issue| {
+            issue.diagnostic.code == "unallocated_leaf"
+                && issue.diagnostic.message.contains("Second")
+        })
+        .unwrap();
+    assert_eq!(issue.path, "parts/a.arcadia");
+    assert_eq!(issue.diagnostic.line, 3);
+    assert_eq!(issue.diagnostic.column, 1);
+    let span = issue.diagnostic.span;
+    assert_eq!(span.start, raw.find("sa_function second").unwrap());
+    assert_eq!(
+        &raw[span.start..span.end],
+        "sa_function second \"Second\" {}"
+    );
+    let compiled = compile_bundle(&disk.reachable_bundle(), ProjectLimits::default()).unwrap();
+    assert_ne!(compiled.bundle, disk.bundle);
+    assert!(compiled.diagnostics.iter().any(|later| {
+        later.diagnostic.code == issue.diagnostic.code
+            && later.diagnostic.message == issue.diagnostic.message
+            && later.diagnostic.span.start > span.start
+    }));
+    assert_eq!(fs::read_to_string(path).unwrap(), raw);
+}
+
+#[test]
+fn discovery_diagnoses_legacy_semantics_before_source_rewrite() {
+    let directory = tempfile::tempdir().unwrap();
+    let path = directory.path().join("project.arcadia");
+    let raw = include_str!("fixtures/v3-data-contract.arcadia");
+    fs::write(&path, raw).unwrap();
+    let disk = load_project(&path, ProjectLimits::default()).unwrap();
+    assert_eq!(disk.bundle.files["project.arcadia"], raw);
+    assert!(!disk.diagnostics.is_empty());
+    assert!(
+        disk.diagnostics
+            .iter()
+            .all(|issue| { issue.diagnostic.severity == oa_core::validation::Severity::Warning })
+    );
+    assert_eq!(
+        disk.diagnostics,
+        lint_bundle(&disk.reachable_bundle(), ProjectLimits::default())
+    );
+    let compiled = compile_bundle(&disk.reachable_bundle(), ProjectLimits::default()).unwrap();
+    assert_eq!(compiled.decoded.migration.as_ref().unwrap().from_schema, 3);
+    assert_ne!(compiled.bundle, disk.bundle);
+    for issue in &disk.diagnostics {
+        assert!(compiled.diagnostics.iter().any(|later| {
+            later.diagnostic.code == issue.diagnostic.code
+                && later.diagnostic.object_id == issue.diagnostic.object_id
+                && later.diagnostic.message == issue.diagnostic.message
+        }));
+        let span = issue.diagnostic.span;
+        assert!(raw.get(span.start..span.end).is_some());
+    }
+    // Invalid legacy references still fail during semantic resolution on the
+    // authored bytes; deferring the source rewrite does not hide those errors.
+    let invalid = raw.replace("@coordinate", "@missing");
+    fs::write(&path, &invalid).unwrap();
+    let broken = load_project(&path, ProjectLimits::default()).unwrap();
+    assert!(broken.diagnostics.iter().any(|issue| {
+        issue.diagnostic.severity == oa_core::validation::Severity::Error
+            && issue.diagnostic.message.contains("@missing")
+    }));
+    assert_eq!(broken.bundle.files["project.arcadia"], invalid);
+    assert!(compile_bundle(&broken.reachable_bundle(), ProjectLimits::default()).is_err());
+    assert_eq!(fs::read_to_string(path).unwrap(), invalid);
+}

crates/oa-core/tests/state_diagrams.rs

@@ -20,6 +20,7 @@ fn view(p: &mut Project, machine: Id, alias: &str) -> Id {
             projection: ProjectionKind::StateMachine { machine },
             view_options: Default::default(),
             nodes: BTreeMap::new(),
+            layout: None,
             routes: vec![],
         },
     );
@@ -301,6 +302,8 @@ fn folding_retains_authored_routes_without_false_self_transitions() {
     let pins = vec![point(690., 480.), point(690., 230.)];
     f.p.diagrams.get_mut(&f.d).unwrap().routes.push(EdgeRoute {
         edge: out,
+        source_attachment: None,
+        target_attachment: None,
         waypoints: pins.clone(),
         label: None,
     });
@@ -362,11 +365,15 @@ fn grouped_moves_translate_hidden_descendants_and_pins_only_in_one_view() {
     let pins = vec![point(570., 460.)];
     f.p.diagrams.get_mut(&f.d).unwrap().routes.push(EdgeRoute {
         edge: f.local,
+        source_attachment: None,
+        target_attachment: None,
         waypoints: pins.clone(),
         label: Some(label.clone()),
     });
     f.p.diagrams.get_mut(&f.d).unwrap().routes.push(EdgeRoute {
         edge: f.external,
+        source_attachment: None,
+        target_attachment: None,
         waypoints: vec![point(690., 230.)],
         label: None,
     });
@@ -422,6 +429,8 @@ fn cross_machine_reparent_requires_atomic_placement_and_route_repair() {
     let placement = f.p.place(f.d, orphan, point(30., 750.));
     f.p.diagrams.get_mut(&f.d).unwrap().routes.push(EdgeRoute {
         edge,
+        source_attachment: None,
+        target_attachment: None,
         waypoints: vec![],
         label: None,
     });
@@ -456,6 +465,8 @@ fn cross_machine_reparent_requires_atomic_placement_and_route_repair() {
                 diagram: other,
                 route: EdgeRoute {
                     edge,
+                    source_attachment: None,
+                    target_attachment: None,
                     waypoints: vec![],
                     label: None,
                 },
@@ -583,6 +594,8 @@ fn layout_reserves_internal_rows_and_state_routes_retain_hard_pins() {
     let pins = vec![point(730., 130.), point(1060., 130.)];
     f.p.diagrams.get_mut(&f.d).unwrap().routes.push(EdgeRoute {
         edge: f.self_edge,
+        source_attachment: None,
+        target_attachment: None,
         waypoints: pins.clone(),
         label: Some(EdgeLabel {
             fraction: 0.25,
@@ -652,6 +665,8 @@ fn moving_a_region_does_not_translate_pins_attached_to_a_stationary_state_bounda
     let pins = vec![point(280., 390.), point(280., 470.)];
     f.p.diagrams.get_mut(&f.d).unwrap().routes.push(EdgeRoute {
         edge: f.local,
+        source_attachment: None,
+        target_attachment: None,
         waypoints: pins.clone(),
         label: None,
     });
@@ -730,6 +745,8 @@ fn initial_transition_attaches_to_the_compact_symbol_and_preview_keeps_settled_g
     );
     f.p.diagrams.get_mut(&f.d).unwrap().routes.push(EdgeRoute {
         edge: f.self_edge,
+        source_attachment: None,
+        target_attachment: None,
         waypoints: vec![],
         label: Some(EdgeLabel {
             fraction: 0.3,

crates/oa-core/tests/transition_counterpart_compatibility.rs

@@ -0,0 +1,353 @@
+//! Existing counterpart eligibility is a layer/category/kind decision, not
+//! validation or acceptance of an entire transition plan. The catalog fixtures
+//! below intentionally contain partial records (unowned states, etc.). The
+//! final regression separately starts from a structurally valid real project.
+use oa_core::{transitions::*, *};
+use std::collections::{BTreeMap, BTreeSet};
+
+fn element(p: &mut Project, layer: Layer, kind: Kind) -> Id {
+    let id = Id::new_v4();
+    let body = if kind == Kind::Port {
+        // Legacy ports can exist in preserved OA models. This does not offer
+        // new typed SA implementation ports for creation in portless OA.
+        ElementBody::shared_in(
+            layer,
+            SharedBody::Port {
+                contract: PortContract::Legacy,
+                legacy: None,
+            },
+        )
+    } else {
+        ElementBody::new(kind, layer).unwrap()
+    };
+    p.elements.insert(
+        id,
+        Element {
+            id,
+            alias: format!("candidate_{}", id.simple()),
+            name: "Identical candidate label".into(),
+            description: String::new(),
+            parent: None,
+            body,
+        },
+    );
+    id
+}
+
+#[test]
+fn existing_element_candidates_obey_explicit_engineering_families_in_both_directions() {
+    // Contract: language.rst §5 trace families and the explicit capability /
+    // mission alternative. State constructors remain eligible for explicit
+    // review across the state family; selecting a candidate does not accept a
+    // constructor change or make invalid ownership legal.
+    let mut allowed: BTreeSet<(Kind, Kind)> = [
+        (Kind::Activity, Kind::Function),
+        (Kind::Entity, Kind::System),
+        (Kind::Entity, Kind::SystemActor),
+        (Kind::Actor, Kind::System),
+        (Kind::Actor, Kind::SystemActor),
+        (Kind::Capability, Kind::SystemCapability),
+        (Kind::OperationalMission, Kind::Mission),
+        (Kind::Capability, Kind::Mission),
+        (Kind::Process, Kind::FunctionalChain),
+    ]
+    .into_iter()
+    .collect();
+    for kind in [
+        Kind::ExchangeItem,
+        Kind::ExchangeCategory,
+        Kind::DataType,
+        Kind::DataField,
+        Kind::Interface,
+        Kind::Port,
+        Kind::Scenario,
+        Kind::Lifeline,
+        Kind::Occurrence,
+        Kind::StateMachine,
+        Kind::Region,
+        Kind::Event,
+        Kind::Constraint,
+    ] {
+        allowed.insert((kind, kind));
+    }
+    let vertices = [
+        Kind::State,
+        Kind::Mode,
+        Kind::Initial,
+        Kind::Final,
+        Kind::Choice,
+        Kind::Junction,
+        Kind::Fork,
+        Kind::Join,
+        Kind::ShallowHistory,
+        Kind::DeepHistory,
+        Kind::EntryPoint,
+        Kind::ExitPoint,
+        Kind::Terminate,
+    ];
+    for oa in vertices {
+        for sa in vertices {
+            allowed.insert((oa, sa));
+        }
+    }
+    let mut p = Project::empty();
+    let oa: BTreeMap<_, _> = Kind::ALL
+        .into_iter()
+        .filter(|kind| kind.supports(Layer::Oa))
+        .map(|kind| (kind, element(&mut p, Layer::Oa, kind)))
+        .collect();
+    let sa: BTreeMap<_, _> = Kind::ALL
+        .into_iter()
+        .filter(|kind| kind.supports(Layer::Sa))
+        .map(|kind| (kind, element(&mut p, Layer::Sa, kind)))
+        .collect();
+    let original = p.clone();
+    for (&oa_kind, &oa_id) in &oa {
+        for (&sa_kind, &sa_id) in &sa {
+            let expected = allowed.contains(&(oa_kind, sa_kind));
+            assert_eq!(
+                counterpart_compatible(&p, oa_id, sa_id, TransitionDirection::OaToSa),
+                expected,
+                "OA {oa_kind:?} → SA {sa_kind:?}"
+            );
+            assert_eq!(
+                counterpart_compatible(&p, sa_id, oa_id, TransitionDirection::SaToOa),
+                expected,
+                "SA {sa_kind:?} → OA {oa_kind:?}"
+            );
+        }
+    }
+    assert_eq!(
+        p, original,
+        "Eligibility must not establish correspondence or edit records"
+    );
+}
+
+fn relation(p: &mut Project, kind: RelationKind, anchor: Id) -> Id {
+    let id = Id::new_v4();
+    // Only the semantic layer and relation category participate in candidate
+    // eligibility. Endpoint compatibility belongs to full plan validation.
+    p.relations.insert(
+        id,
+        Relation {
+            id,
+            alias: format!("relation_{}", id.simple()),
+            name: "Identical relation label".into(),
+            description: String::new(),
+            body: RelationBody::new(kind, anchor, anchor),
+        },
+    );
+    id
+}
+
+#[test]
+fn existing_relation_candidates_distinguish_work_boundary_and_shared_relations() {
+    // Work and boundary exchanges are different families. The boundary /
+    // boundary pair permits preserved legacy OA boundary records; ordinary
+    // portless OA communication means map to SA boundary exchanges.
+    let mut allowed = vec![
+        (RelationKind::Interaction, RelationKind::FunctionalExchange),
+        (
+            RelationKind::CommunicationMean,
+            RelationKind::BoundaryExchange,
+        ),
+        (
+            RelationKind::BoundaryExchange,
+            RelationKind::BoundaryExchange,
+        ),
+    ];
+    let shared = [
+        RelationKind::Allocation,
+        RelationKind::InterfaceItemAllocation,
+        RelationKind::DataAssociation,
+        RelationKind::ExchangeAllocation,
+        RelationKind::CapabilityInvolvement,
+        RelationKind::CapabilityInclude,
+        RelationKind::CapabilityExtend,
+        RelationKind::CapabilityGeneralization,
+        RelationKind::MissionInvolvement,
+        RelationKind::MissionCapability,
+        RelationKind::SequenceLink,
+        RelationKind::ContextualLink,
+        RelationKind::ChainInvolvement,
+        RelationKind::InterfaceProvision,
+        RelationKind::InterfaceRequirement,
+        RelationKind::StateTransition,
+        RelationKind::Availability,
+        RelationKind::StateAction,
+    ];
+    for kind in shared {
+        allowed.push((kind, kind));
+    }
+    let mut p = Project::empty();
+    let oa_anchor = element(&mut p, Layer::Oa, Kind::Activity);
+    let sa_anchor = element(&mut p, Layer::Sa, Kind::Function);
+    let oa: Vec<_> = shared
+        .into_iter()
+        .chain([
+            RelationKind::Interaction,
+            RelationKind::CommunicationMean,
+            RelationKind::BoundaryExchange,
+            RelationKind::RoleRealization,
+            RelationKind::RoleAssignment,
+        ])
+        .map(|kind| (kind, relation(&mut p, kind, oa_anchor)))
+        .collect();
+    let sa: Vec<_> = shared
+        .into_iter()
+        .chain([
+            RelationKind::FunctionalExchange,
+            RelationKind::BoundaryExchange,
+            RelationKind::PortAllocation,
+        ])
+        .map(|kind| (kind, relation(&mut p, kind, sa_anchor)))
+        .collect();
+    for &(oa_kind, oa_id) in &oa {
+        for &(sa_kind, sa_id) in &sa {
+            let expected = allowed.contains(&(oa_kind, sa_kind));
+            assert_eq!(
+                counterpart_compatible(&p, oa_id, sa_id, TransitionDirection::OaToSa),
+                expected,
+                "OA {oa_kind:?} → SA {sa_kind:?}"
+            );
+            assert_eq!(
+                counterpart_compatible(&p, sa_id, oa_id, TransitionDirection::SaToOa),
+                expected,
+                "SA {sa_kind:?} → OA {oa_kind:?}"
+            );
+        }
+    }
+}
+
+#[test]
+fn candidate_eligibility_rejects_wrong_layers_categories_and_missing_identities() {
+    let mut p = Project::empty();
+    let oa = element(&mut p, Layer::Oa, Kind::Activity);
+    let sa = element(&mut p, Layer::Sa, Kind::Function);
+    let oa_exchange = relation(&mut p, RelationKind::Interaction, oa);
+    let sa_exchange = relation(&mut p, RelationKind::FunctionalExchange, sa);
+    let diagram = p.ensure_diagram(Layer::Sa);
+    let node = p.place(diagram, sa, Position { x: 1., y: 2. });
+    for (direction, source, target, source_relation, target_relation) in [
+        (
+            TransitionDirection::OaToSa,
+            oa,
+            sa,
+            oa_exchange,
+            sa_exchange,
+        ),
+        (
+            TransitionDirection::SaToOa,
+            sa,
+            oa,
+            sa_exchange,
+            oa_exchange,
+        ),
+    ] {
+        assert!(counterpart_compatible(&p, source, target, direction));
+        assert!(counterpart_compatible(
+            &p,
+            source_relation,
+            target_relation,
+            direction
+        ));
+        for (a, b) in [
+            (target, source),
+            (source, source),
+            (target, target),
+            (target_relation, source_relation),
+            (source_relation, source_relation),
+            (source, target_relation),
+            (source_relation, target),
+        ] {
+            assert!(!counterpart_compatible(&p, a, b, direction));
+        }
+        for absent_or_nonsemantic in [Id::nil(), Id::new_v4(), p.id, diagram, node] {
+            assert!(!counterpart_compatible(
+                &p,
+                source,
+                absent_or_nonsemantic,
+                direction
+            ));
+            assert!(!counterpart_compatible(
+                &p,
+                absent_or_nonsemantic,
+                target,
+                direction
+            ));
+        }
+    }
+    p.elements.remove(&sa);
+    assert!(!counterpart_compatible(
+        &p,
+        oa,
+        sa,
+        TransitionDirection::OaToSa
+    ));
+    assert!(!counterpart_compatible(
+        &p,
+        sa,
+        oa,
+        TransitionDirection::SaToOa
+    ));
+    // The retained relation header cannot borrow a layer from a deleted owner.
+    assert!(!counterpart_compatible(
+        &p,
+        oa_exchange,
+        sa_exchange,
+        TransitionDirection::OaToSa
+    ));
+}
+
+#[test]
+fn activity_picker_rejects_real_sa_port_and_agrees_with_explicit_plan_refusal() {
+    let p = Project::demo();
+    let original = p.clone();
+    assert!(validation::validate(&p).is_empty());
+    let source = p
+        .elements
+        .values()
+        .find(|e| e.kind() == Kind::Activity)
+        .unwrap()
+        .id;
+    let port = p
+        .elements
+        .values()
+        .find(|e| e.layer() == Layer::Sa && e.kind() == Kind::Port)
+        .unwrap()
+        .id;
+    let function = p
+        .elements
+        .values()
+        .find(|e| e.kind() == Kind::Function)
+        .unwrap()
+        .id;
+    assert!(counterpart_compatible(
+        &p,
+        source,
+        function,
+        TransitionDirection::OaToSa
+    ));
+    assert!(!counterpart_compatible(
+        &p,
+        source,
+        port,
+        TransitionDirection::OaToSa
+    ));
+    let mut request = TransitionRequest::new(TransitionDirection::OaToSa, vec![source]);
+    request.mappings.push(TransitionMapping {
+        source,
+        target: Some(port),
+        target_kind: None,
+    });
+    let plan = plan_transition(&p, &request).unwrap();
+    assert!(
+        plan.conflicts
+            .iter()
+            .any(|conflict| conflict.source == Some(source)
+                && conflict.target == Some(port)
+                && conflict.field.is_none())
+    );
+    assert!(apply_transition(&p, &plan).is_err());
+    assert_eq!(p, original);
+}

crates/oa-core/tests/transition_lifecycle.rs

@@ -0,0 +1,638 @@
+//! Endpoint lifecycle acceptance for the ordinary, prose-reviewed transition API.
+//! OA is portless; the SA half contains typed ports. Deletion expectations below
+//! are fixture-owned identity lists, never results of the deletion implementation.
+use oa_core::{
+    language, persistence,
+    source_project::{ProjectLimits, SourceBundle, compile_bundle},
+    transitions::*,
+    validation::{self, Severity},
+    *,
+};
+use std::collections::BTreeMap;
+
+struct Side {
+    root: Id,
+    elements: Vec<Id>,
+    exchange: Id,
+    diagram: Id,
+    nodes: Vec<Id>,
+    artifacts: Vec<Id>,
+}
+
+struct Fixture {
+    project: Project,
+    source: Side,
+    target: Side,
+    trace: Id,
+    trace_artifact: Id,
+}
+
+fn artifact(p: &mut Project, owner: Id, label: &str) -> Id {
+    let id = Id::new_v4();
+    p.artifact_links.insert(
+        id,
+        ArtifactLink {
+            id,
+            alias: p.fresh_alias(label, "evidence", id),
+            name: label.into(),
+            description: "Independently authored rationale".into(),
+            owner,
+            relation: ArtifactRelation::References,
+            uri: "git:engineering/design.md".into(),
+            revision: Some("review-17".into()),
+            fragment: Some("retained-decision".into()),
+        },
+    );
+    id
+}
+
+fn side(p: &mut Project, layer: Layer) -> Side {
+    let (kind, prefix, relation) = match layer {
+        Layer::Oa => (Kind::Activity, "Operational", RelationKind::Interaction),
+        Layer::Sa => (
+            Kind::Function,
+            "Technical",
+            RelationKind::FunctionalExchange,
+        ),
+    };
+    let root = p
+        .add_element(kind, layer, &format!("{prefix} design"), None)
+        .unwrap();
+    p.elements.get_mut(&root).unwrap().description =
+        format!("{prefix} independently reviewed intent");
+    let send = p
+        .add_element(kind, layer, &format!("{prefix} send"), Some(root))
+        .unwrap();
+    let receive = p
+        .add_element(kind, layer, &format!("{prefix} receive"), Some(root))
+        .unwrap();
+    p.elements.get_mut(&send).unwrap().description =
+        "Preserve the detailed sending responsibility".into();
+    p.elements.get_mut(&receive).unwrap().description =
+        "Preserve the detailed receiving responsibility".into();
+    // A shared, separately owned definition survives deletion of its users.
+    let item = p
+        .add_element(
+            Kind::ExchangeItem,
+            layer,
+            &format!("{prefix} information"),
+            None,
+        )
+        .unwrap();
+    *p.elements.get_mut(&item).unwrap().shared_mut().unwrap() = SharedBody::ExchangeItem {
+        kind: ExchangeItemKind::Information,
+        mechanism: ExchangeMechanism::Flow,
+        supertype: None,
+    };
+    p.add_element(
+        Kind::DataField,
+        layer,
+        &format!("{prefix} payload"),
+        Some(item),
+    )
+    .unwrap();
+    let exchange = p.relate(relation, &format!("{prefix} delivery"), send, receive);
+    let mut elements = vec![root, send, receive];
+    match &mut p.relations.get_mut(&exchange).unwrap().body {
+        RelationBody::Interaction { items, .. } => *items = vec![item],
+        RelationBody::FunctionalExchange {
+            items,
+            source_port,
+            target_port,
+            ..
+        } => {
+            *items = vec![item];
+            let (output, input) = (*source_port, *target_port);
+            *p.elements.get_mut(&output).unwrap().shared_mut().unwrap() = SharedBody::Port {
+                contract: PortContract::FunctionOutput {
+                    outgoing_items: vec![item],
+                },
+                legacy: None,
+            };
+            *p.elements.get_mut(&input).unwrap().shared_mut().unwrap() = SharedBody::Port {
+                contract: PortContract::FunctionInput {
+                    incoming_items: vec![item],
+                },
+                legacy: None,
+            };
+            elements.extend([output, input]);
+        }
+        _ => unreachable!(),
+    }
+    p.relations.get_mut(&exchange).unwrap().description =
+        "Retain direction, item contract and relation identity".into();
+    let diagram = p.ensure_diagram(layer);
+    p.diagrams.get_mut(&diagram).unwrap().projection = ProjectionKind::Decomposition;
+    let nodes = [root, send, receive]
+        .into_iter()
+        .enumerate()
+        .map(|(index, element)| {
+            p.place(
+                diagram,
+                element,
+                Position {
+                    x: 43.25 + index as f32 * 271.,
+                    y: 97.5 + index as f32 * 83.,
+                },
+            )
+        })
+        .collect::<Vec<_>>();
+    let root_node = p
+        .diagrams
+        .get_mut(&diagram)
+        .unwrap()
+        .nodes
+        .get_mut(&nodes[0])
+        .unwrap();
+    root_node.size = Size {
+        width: 611.,
+        height: 319.,
+    };
+    root_node.collapsed = true;
+    p.diagrams
+        .get_mut(&diagram)
+        .unwrap()
+        .routes
+        .push(EdgeRoute {
+            edge: exchange,
+            // Both directions must preserve authored endpoint preferences,
+            // including dormant preferences on the SA semantic-port edge.
+            source_attachment: Some(EdgeAttachment {
+                side: PortAnchorSide::Bottom,
+                offset: 0.2,
+            }),
+            target_attachment: Some(EdgeAttachment {
+                side: PortAnchorSide::Top,
+                offset: 0.8,
+            }),
+            waypoints: vec![Position {
+                x: 337.5,
+                y: 423.25,
+            }],
+            label: Some(EdgeLabel {
+                fraction: 0.7,
+                offset: Position { x: 11., y: -17. },
+            }),
+        });
+    let artifacts = [root, send, exchange, nodes[0]]
+        .into_iter()
+        .enumerate()
+        .map(|(index, owner)| artifact(p, owner, &format!("{prefix} evidence {index}")))
+        .collect();
+    artifact(p, item, &format!("{prefix} shared item evidence"));
+    Side {
+        root,
+        elements,
+        exchange,
+        diagram,
+        nodes,
+        artifacts,
+    }
+}
+
+fn accepted(p: &Project) {
+    let issues = validation::validate(p);
+    // This fixture deliberately isolates decomposition and correspondence from
+    // performer allocation and process/chain/scenario inclusion. Each surviving
+    // leaf (including a newly transitioned root) must have exactly those two
+    // incomplete-work warnings; each surviving local exchange lacks a behavior
+    // context. Check exact record IDs and fields, including duplicate warnings.
+    // The system of interest and item contracts are complete fixture facts.
+    assert!(
+        issues
+            .iter()
+            .all(|issue| issue.severity == Severity::Warning),
+        "{issues:?}"
+    );
+    let mut expected = Vec::new();
+    for element in p.elements.values().filter(|element| {
+        matches!(element.kind(), Kind::Activity | Kind::Function)
+            && !p
+                .elements
+                .values()
+                .any(|child| child.parent == Some(element.id) && child.kind() == element.kind())
+    }) {
+        expected.push(("unallocated_leaf", Some(element.id), Some("allocation")));
+        expected.push(("work_without_behavior_context", Some(element.id), None));
+    }
+    for relation in p.relations.values().filter(|relation| {
+        matches!(
+            relation.kind(),
+            RelationKind::Interaction | RelationKind::FunctionalExchange
+        )
+    }) {
+        expected.push(("exchange_without_behavior_context", Some(relation.id), None));
+    }
+    let mut actual = issues
+        .iter()
+        .map(|issue| (issue.code.as_str(), issue.element, issue.field.as_deref()))
+        .collect::<Vec<_>>();
+    expected.sort();
+    actual.sort();
+    assert_eq!(
+        actual, expected,
+        "Unexpected fixture diagnostics: {issues:?}"
+    );
+}
+
+fn round_trip(p: &Project) -> String {
+    accepted(p);
+    let json = serde_json::to_vec_pretty(p).unwrap();
+    assert_eq!(persistence::decode(&json).unwrap(), *p);
+    let source = language::format(p);
+    let compiled = compile_bundle(
+        &SourceBundle {
+            entry: "project.arcadia".into(),
+            files: BTreeMap::from([("project.arcadia".into(), source.clone())]),
+        },
+        ProjectLimits::default(),
+    )
+    .unwrap();
+    assert_eq!(compiled.decoded.project, *p);
+    assert_eq!(language::format(&compiled.decoded.project), source);
+    source
+}
+
+fn explicit(direction: TransitionDirection, source: Id, target: Id) -> TransitionRequest {
+    let mut request = TransitionRequest::new(direction, vec![source]);
+    request.mappings.push(TransitionMapping {
+        source,
+        target: Some(target),
+        target_kind: None,
+    });
+    request
+}
+
+fn fixture(direction: TransitionDirection) -> Fixture {
+    let mut project = Project::empty();
+    project.name = "Endpoint lifecycle conservation".into();
+    project
+        .add_element(Kind::System, Layer::Sa, "System of interest", None)
+        .unwrap();
+    let oa = side(&mut project, Layer::Oa);
+    let sa = side(&mut project, Layer::Sa);
+    let (source, target) = match direction {
+        TransitionDirection::OaToSa => (oa, sa),
+        TransitionDirection::SaToOa => (sa, oa),
+    };
+    accepted(&project);
+    let before = project.clone();
+    let mut request = explicit(direction, source.root, target.root);
+    for field in [TransitionField::Name, TransitionField::Description] {
+        request.resolutions.push(FieldResolution {
+            source: source.root,
+            field,
+            decision: FieldDecision::KeepTarget,
+        });
+    }
+    let plan = plan_transition(&project, &request).unwrap();
+    assert!(plan.conflicts.is_empty(), "{:?}", plan.conflicts);
+    project = apply_transition(&project, &plan).unwrap();
+    let trace = assert_only_new_trace(&before, &project, direction, source.root, target.root);
+    let mut without_trace = project.clone();
+    without_trace.traces.remove(&trace);
+    assert_eq!(
+        without_trace, before,
+        "Initial review must only add correspondence"
+    );
+    let trace_artifact = artifact(&mut project, trace, "Correspondence rationale");
+    round_trip(&project);
+    Fixture {
+        project,
+        source,
+        target,
+        trace,
+        trace_artifact,
+    }
+}
+
+fn assert_only_new_trace(
+    before: &Project,
+    after: &Project,
+    direction: TransitionDirection,
+    source: Id,
+    target: Id,
+) -> Id {
+    let added = after
+        .traces
+        .values()
+        .filter(|trace| !before.traces.contains_key(&trace.id))
+        .collect::<Vec<_>>();
+    assert_eq!(added.len(), 1);
+    assert_eq!(after.traces.len(), before.traces.len() + 1);
+    let trace = added[0];
+    let (oa, sa) = match direction {
+        TransitionDirection::OaToSa => (source, target),
+        TransitionDirection::SaToOa => (target, source),
+    };
+    assert_eq!(
+        (trace.oa, trace.sa, trace.kind),
+        (oa, sa, TraceKind::Refinement)
+    );
+    assert_eq!(
+        trace.baseline,
+        Some(TraceBaseline {
+            oa: after.properties(oa).unwrap(),
+            sa: after.properties(sa).unwrap(),
+            semantic: None,
+        })
+    );
+    assert_eq!(trace_drift(after, trace), Drift::Unchanged);
+    trace.id
+}
+
+fn expected_deletion(fixture: &Fixture, side: &Side) -> Project {
+    let mut expected = fixture.project.clone();
+    for id in &side.elements {
+        assert!(expected.elements.remove(id).is_some());
+    }
+    assert!(expected.relations.remove(&side.exchange).is_some());
+    assert!(expected.traces.remove(&fixture.trace).is_some());
+    for id in side.artifacts.iter().chain([&fixture.trace_artifact]) {
+        assert!(expected.artifact_links.remove(id).is_some());
+    }
+    let diagram = expected.diagrams.get_mut(&side.diagram).unwrap();
+    for id in &side.nodes {
+        assert!(diagram.nodes.remove(id).is_some());
+    }
+    // This fixture authored exactly one route, for its removed local exchange.
+    assert_eq!(diagram.routes.len(), 1);
+    assert_eq!(diagram.routes[0].edge, side.exchange);
+    diagram.routes.clear();
+    expected
+}
+
+fn unchanged_retry(p: &Project, direction: TransitionDirection, source: Id, target: Id) {
+    let request = TransitionRequest::new(direction, vec![source]);
+    let plan = plan_transition(p, &request).unwrap();
+    assert!(plan.conflicts.is_empty(), "{:?}", plan.conflicts);
+    assert_eq!(plan.changes.len(), 1);
+    assert_eq!(
+        (
+            plan.changes[0].source,
+            plan.changes[0].target,
+            plan.changes[0].action
+        ),
+        (source, target, TransitionAction::Reuse)
+    );
+    assert!(plan.changes[0].fields.is_empty());
+    assert!(plan.commands.is_empty(), "{:?}", plan.commands);
+    let mut session = Session::new(p.clone());
+    let revision = session.revision();
+    session
+        .execute(Command::Replace(apply_transition(p, &plan).unwrap()))
+        .unwrap();
+    assert_eq!(session.project(), p);
+    assert_eq!(session.revision(), revision);
+    assert!(!session.can_undo());
+}
+
+fn source_deletion(direction: TransitionDirection) {
+    let fixture = fixture(direction);
+    let original_source = round_trip(&fixture.project);
+    let expected = expected_deletion(&fixture, &fixture.source);
+    let mut session = Session::new(fixture.project.clone());
+    session
+        .execute(Command::Delete(fixture.source.root))
+        .unwrap();
+    // Whole-project equality covers every retained target child, typed SA port,
+    // exchange, placement, route, artifact, shared item and unchanged identity.
+    assert_eq!(session.project(), &expected);
+    let deleted_source = round_trip(session.project());
+    session.undo();
+    assert_eq!(session.project(), &fixture.project);
+    assert_eq!(round_trip(session.project()), original_source);
+    assert!(!session.can_undo(), "Deletion is one history transaction");
+    session.redo();
+    assert_eq!(session.project(), &expected);
+    assert_eq!(round_trip(session.project()), deleted_source);
+}
+
+fn implicit_creation(
+    p: &Project,
+    direction: TransitionDirection,
+    source: Id,
+    forbidden_target: Id,
+) -> (Project, Id) {
+    let request = TransitionRequest::new(direction, vec![source]);
+    let plan = plan_transition(p, &request).unwrap();
+    assert!(plan.conflicts.is_empty(), "{:?}", plan.conflicts);
+    assert_eq!(plan.changes.len(), 1);
+    let change = &plan.changes[0];
+    assert_eq!(change.source, source);
+    assert_eq!(change.action, TransitionAction::Create);
+    let target = change.target;
+    assert_ne!(target, forbidden_target);
+    assert!(!p.contains(target));
+    let after = apply_transition(p, &plan).unwrap();
+    let trace = assert_only_new_trace(p, &after, direction, source, target);
+    let created = &after.elements[&target];
+    assert_eq!(created.id, target, "Apply preserves the preview identity");
+    assert_eq!(created.name, p.elements[&source].name);
+    assert_eq!(created.description, p.elements[&source].description);
+    assert_eq!(created.parent, None);
+    assert_eq!(
+        created.body,
+        match direction {
+            TransitionDirection::OaToSa => ElementBody::Sa(SaBody::Function),
+            TransitionDirection::SaToOa => ElementBody::Oa(OaBody::Activity),
+        }
+    );
+    assert!(!created.alias.is_empty());
+    assert!(
+        !p.identities()
+            .iter()
+            .any(|(_, alias)| *alias == created.alias)
+    );
+    // Remove only the independently expected two additions. Any incidental
+    // mutation, clone of target children or extra correspondence fails here.
+    let mut retained = after.clone();
+    retained.elements.remove(&target);
+    retained.traces.remove(&trace);
+    assert_eq!(retained, *p);
+    round_trip(&after);
+    // Replaying a creation plan after acceptance violates its snapshot, while
+    // a fresh unchanged request reuses the accepted counterpart.
+    assert!(
+        apply_transition(&after, &plan)
+            .unwrap_err()
+            .0
+            .contains("stale")
+    );
+    unchanged_retry(&after, direction, source, target);
+    (after, target)
+}
+
+fn target_deletion(direction: TransitionDirection) {
+    let fixture = fixture(direction);
+    let request = TransitionRequest::new(direction, vec![fixture.source.root]);
+    let old_plan = plan_transition(&fixture.project, &request).unwrap();
+    assert!(old_plan.conflicts.is_empty());
+    let expected = expected_deletion(&fixture, &fixture.target);
+    let mut session = Session::new(fixture.project.clone());
+    session
+        .execute(Command::Delete(fixture.target.root))
+        .unwrap();
+    assert_eq!(session.project(), &expected);
+    round_trip(session.project());
+    let revision = session.revision();
+    assert!(
+        apply_transition(session.project(), &old_plan)
+            .unwrap_err()
+            .0
+            .contains("stale")
+    );
+    let explicit_plan = plan_transition(
+        session.project(),
+        &explicit(direction, fixture.source.root, fixture.target.root),
+    )
+    .unwrap();
+    assert!(
+        explicit_plan
+            .conflicts
+            .iter()
+            .any(|conflict| conflict.source == Some(fixture.source.root)
+                && conflict.target == Some(fixture.target.root)
+                && conflict.field.is_none())
+    );
+    assert!(apply_transition(session.project(), &explicit_plan).is_err());
+    assert_eq!(session.project(), &expected);
+    assert_eq!(session.revision(), revision);
+    let (created, _) = implicit_creation(
+        session.project(),
+        direction,
+        fixture.source.root,
+        fixture.target.root,
+    );
+    session.execute(Command::Replace(created.clone())).unwrap();
+    session.undo();
+    assert_eq!(session.project(), &expected);
+    session.undo();
+    assert_eq!(session.project(), &fixture.project);
+    assert!(!session.can_undo());
+    session.redo();
+    session.redo();
+    assert_eq!(session.project(), &created);
+    round_trip(session.project());
+}
+
+fn source_recreation(direction: TransitionDirection) {
+    let fixture = fixture(direction);
+    let mut replacement = fixture.project.elements[&fixture.source.root].clone();
+    replacement.id = Id::new_v4();
+    let source = replacement.id;
+    // Same alias, name and prose, different UUID: name matching must never
+    // silently relink the retained engineering design.
+    assert_ne!(source, fixture.source.root);
+    let deleted = execute_batch(&fixture.project, &[Command::Delete(fixture.source.root)]).unwrap();
+    assert_eq!(deleted, expected_deletion(&fixture, &fixture.source));
+    let recreated =
+        execute_batch(&deleted, &[Command::CreateElement(replacement.clone())]).unwrap();
+    let mut expected = deleted.clone();
+    expected.elements.insert(source, replacement);
+    assert_eq!(recreated, expected);
+    round_trip(&recreated);
+    let (implicit, new_target) =
+        implicit_creation(&recreated, direction, source, fixture.target.root);
+    assert!(implicit.elements.contains_key(&fixture.target.root));
+    assert_ne!(new_target, fixture.target.root);
+
+    // The explicit branch starts from exactly the same recreated project.
+    let mut request = explicit(direction, source, fixture.target.root);
+    let unreviewed = plan_transition(&recreated, &request).unwrap();
+    for field in [TransitionField::Name, TransitionField::Description] {
+        assert!(
+            unreviewed
+                .conflicts
+                .iter()
+                .any(|conflict| conflict.source == Some(source)
+                    && conflict.target == Some(fixture.target.root)
+                    && conflict.field == Some(field))
+        );
+    }
+    assert!(apply_transition(&recreated, &unreviewed).is_err());
+    request.resolutions = vec![
+        FieldResolution {
+            source,
+            field: TransitionField::Name,
+            decision: FieldDecision::TakeSource,
+        },
+        FieldResolution {
+            source,
+            field: TransitionField::Description,
+            decision: FieldDecision::KeepTarget,
+        },
+    ];
+    let plan = plan_transition(&recreated, &request).unwrap();
+    assert!(plan.conflicts.is_empty(), "{:?}", plan.conflicts);
+    assert_eq!(plan.changes.len(), 1);
+    assert_eq!(
+        (plan.changes[0].target, plan.changes[0].action),
+        (fixture.target.root, TransitionAction::Update)
+    );
+    assert_eq!(
+        plan.changes[0].fields,
+        vec![FieldChange {
+            field: TransitionField::Name,
+            before: recreated.elements[&fixture.target.root].name.clone(),
+            after: recreated.elements[&source].name.clone(),
+        }]
+    );
+    let relinked = apply_transition(&recreated, &plan).unwrap();
+    let new_trace = assert_only_new_trace(
+        &recreated,
+        &relinked,
+        direction,
+        source,
+        fixture.target.root,
+    );
+    assert_ne!(
+        new_trace, fixture.trace,
+        "Deleted correspondence is not silently resurrected"
+    );
+    let mut expected = recreated.clone();
+    expected
+        .elements
+        .get_mut(&fixture.target.root)
+        .unwrap()
+        .name = recreated.elements[&source].name.clone();
+    let mut without_trace = relinked.clone();
+    without_trace.traces.remove(&new_trace);
+    assert_eq!(
+        without_trace, expected,
+        "Only the reviewed target name may change; rich target design survives"
+    );
+    round_trip(&relinked);
+    unchanged_retry(&relinked, direction, source, fixture.target.root);
+    let original_source = round_trip(&recreated);
+    let mut session = Session::new(recreated.clone());
+    session.execute(Command::Replace(relinked)).unwrap();
+    session.undo();
+    assert_eq!(session.project(), &recreated);
+    assert_eq!(round_trip(session.project()), original_source);
+}
+
+#[test]
+fn oa_source_deletion_preserves_rich_sa_design_and_exact_undo() {
+    source_deletion(TransitionDirection::OaToSa);
+}
+#[test]
+fn sa_source_deletion_preserves_rich_portless_oa_design_and_exact_undo() {
+    source_deletion(TransitionDirection::SaToOa);
+}
+#[test]
+fn deleted_sa_target_refuses_old_plans_and_implicit_retry_creates_once() {
+    target_deletion(TransitionDirection::OaToSa);
+}
+#[test]
+fn deleted_oa_target_refuses_old_plans_and_implicit_retry_creates_once() {
+    target_deletion(TransitionDirection::SaToOa);
+}
+#[test]
+fn recreated_oa_identity_requires_explicit_relink_to_retained_sa_design() {
+    source_recreation(TransitionDirection::OaToSa);
+}
+#[test]
+fn recreated_sa_identity_requires_explicit_relink_to_retained_oa_design() {
+    source_recreation(TransitionDirection::SaToOa);
+}

crates/oa-desktop/Cargo.toml

@@ -18,6 +18,7 @@ serde_json.workspace = true
 reqwest = { version = "0.12", default-features = false, features = ["json", "rustls-tls"] }
 tokio = { version = "1", features = ["rt", "time"] }
 tempfile = "3"
+unicode-segmentation = "1.13.3"
 
 [dev-dependencies]
 iced_runtime = "0.14"

crates/oa-desktop/src/allocation_drag.rs

@@ -0,0 +1,836 @@
+//! Pure, bounded allocation-drag composition. See the v2 interaction contract.
+//!
+//! These values are not input capabilities. The App must independently admit a
+//! clean press and retire its token on every document/input/camera lifetime
+//! change. Cache a SemanticPlan per token and destination; only `place` belongs
+//! on pointer motion. `finish` rechecks the live accepted Project and commands,
+//! but Document::execute still owns source admission and atomic history.
+use oa_core::{
+    projection::{self, ProjectedNode, ProjectedView},
+    validation::{self, Issue, Severity},
+    view_options::ViewIndex,
+    *,
+};
+use std::collections::{BTreeMap, BTreeSet};
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub enum Destination {
+    LayoutOnly,
+    Performer(Id),
+    OutsidePerformers,
+}
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub enum Uniform {
+    Assigned(Id),
+    Unassigned,
+    MixedOrUnresolved,
+}
+
+#[derive(Debug, Clone, PartialEq)]
+pub struct Leaf {
+    pub direct: Option<Relation>,
+    pub role_assignments: Vec<Relation>,
+    pub role_realizations: Vec<Relation>,
+    pub effective_performer: Option<Id>,
+}
+
+/// Exact semantic scope S, leaf scope L and active placement scope Q, including
+/// folded/unplaced leaves. Retaining records detects first-child responsibility
+/// transfer. Revision and input-epoch guards remain the caller's responsibility.
+#[derive(Debug, Clone, PartialEq)]
+pub struct Scope {
+    pub project: Id,
+    pub work: Id,
+    pub placement: Id,
+    pub work_records: BTreeMap<Id, Element>,
+    pub leaves: BTreeMap<Id, Leaf>,
+    pub placements: BTreeMap<Id, NodePlacement>,
+    pub diagram: Diagram,
+    pub uniform: Uniform,
+}
+
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub struct ChangedRecord {
+    pub id: Id,
+    pub name: String,
+    pub category: &'static str,
+}
+
+#[derive(Debug, Clone, PartialEq)]
+pub enum Refusal {
+    Ineligible(String),
+    StaleScope,
+    MixedLayoutRequired,
+    RoleExitRequired {
+        work: Id,
+        roles: Vec<Id>,
+        performers: Vec<Id>,
+        message: String,
+    },
+    MissingAllocationId(Id),
+    InvalidCandidate(String),
+    CollateralChangeRequired(Vec<ChangedRecord>),
+    LayoutRequired(String),
+}
+
+pub fn capture(p: &Project, diagram: Id, work: Id, placement: Id) -> Result<Scope, Refusal> {
+    validate_candidate(p).map_err(|e| Refusal::InvalidCandidate(e.to_string()))?;
+    let d = p.diagrams.get(&diagram).ok_or(Refusal::StaleScope)?;
+    let root = p.elements.get(&work).ok_or(Refusal::StaleScope)?;
+    if !root.kind().is_work()
+        || d.projection != ProjectionKind::Allocation
+        || d.layer != root.layer()
+    {
+        return Err(Refusal::Ineligible(
+            "Select an activity or function in an Allocation view.".into(),
+        ));
+    }
+    if d.nodes.get(&placement).is_none_or(|n| n.element != work) {
+        return Err(Refusal::StaleScope);
+    }
+    let mut work_records = BTreeMap::new();
+    let mut leaves = BTreeMap::new();
+    let mut pending = vec![work];
+    while let Some(id) = pending.pop() {
+        let element = p.elements.get(&id).ok_or(Refusal::StaleScope)?;
+        if element.kind() != root.kind() || work_records.insert(id, element.clone()).is_some() {
+            return Err(Refusal::StaleScope);
+        }
+        let children: Vec<_> = p
+            .children(id)
+            .filter(|e| e.kind() == root.kind())
+            .map(|e| e.id)
+            .collect();
+        if !children.is_empty() {
+            pending.extend(children);
+            continue;
+        }
+        let direct: Vec<_> = p
+            .relations
+            .values()
+            .filter(|r| r.kind() == RelationKind::Allocation && r.target() == id)
+            .cloned()
+            .collect();
+        if direct.len() > 1 {
+            return Err(Refusal::StaleScope);
+        }
+        let role_assignments: Vec<_> = p
+            .relations
+            .values()
+            .filter(|r| r.kind() == RelationKind::RoleAssignment && r.target() == id)
+            .cloned()
+            .collect();
+        let roles: BTreeSet<_> = role_assignments.iter().map(Relation::source).collect();
+        let role_realizations = p
+            .relations
+            .values()
+            .filter(|r| r.kind() == RelationKind::RoleRealization && roles.contains(&r.target()))
+            .cloned()
+            .collect();
+        leaves.insert(
+            id,
+            Leaf {
+                direct: direct.into_iter().next(),
+                role_assignments,
+                role_realizations,
+                effective_performer: validation::effective_performer(p, id),
+            },
+        );
+    }
+    if leaves.is_empty() {
+        return Err(Refusal::StaleScope);
+    }
+    let uniform = if leaves
+        .values()
+        .all(|l| l.direct.is_none() && l.role_assignments.is_empty())
+    {
+        Uniform::Unassigned
+    } else if let Some(performer) = leaves.values().next().and_then(|l| l.effective_performer)
+        && leaves
+            .values()
+            .all(|l| l.effective_performer == Some(performer))
+    {
+        Uniform::Assigned(performer)
+    } else {
+        Uniform::MixedOrUnresolved
+    };
+    let placements = d
+        .nodes
+        .iter()
+        .filter(|(_, n)| work_records.contains_key(&n.element))
+        .map(|(id, n)| (*id, n.clone()))
+        .collect();
+    Ok(Scope {
+        project: p.id,
+        work,
+        placement,
+        work_records,
+        leaves,
+        placements,
+        diagram: d.clone(),
+        uniform,
+    })
+}
+
+#[derive(Debug)]
+pub struct SemanticPlan {
+    pub scope: Scope,
+    pub destination: Destination,
+    pub label: String,
+    pub warnings: Vec<Issue>,
+    accepted: Project,
+    candidate: Project,
+    index: ViewIndex,
+    commands: Vec<Command>,
+    before_visible: ProjectedView,
+    before_expanded: ProjectedView,
+}
+
+impl SemanticPlan {
+    /// All preview drawing, ports and routing must use this candidate and index.
+    pub fn project(&self) -> &Project {
+        &self.candidate
+    }
+    #[cfg(test)]
+    pub fn index(&self) -> &ViewIndex {
+        &self.index
+    }
+}
+
+/// Allocation identities are allocated once by the gesture owner, keyed by leaf,
+/// and reused on target revisits and release. No random identity generation here.
+pub fn plan_semantics(
+    p: &Project,
+    scope: &Scope,
+    destination: Destination,
+    allocation_ids: &BTreeMap<Id, Id>,
+) -> Result<SemanticPlan, Refusal> {
+    if &capture(p, scope.diagram.id, scope.work, scope.placement)? != scope {
+        return Err(Refusal::StaleScope);
+    }
+    if scope.work_records.len() > 1 && scope.uniform == Uniform::MixedOrUnresolved {
+        return Err(Refusal::MixedLayoutRequired);
+    }
+    if let Destination::Performer(id) = destination {
+        let valid = p
+            .elements
+            .get(&id)
+            .is_some_and(|e| e.kind().is_performer() && e.layer() == scope.diagram.layer);
+        if !valid {
+            return Err(Refusal::Ineligible(
+                "Choose a performer in this layer.".into(),
+            ));
+        }
+    }
+    let before_index = ViewIndex::new(p);
+    let before_visible = projection::project_diagram_with_index(p, &scope.diagram, &before_index);
+    let before_expanded = expanded_view(p, &scope.diagram, scope, &before_index);
+    if scope.work_records.len() > 1 && !coherent(scope, &before_expanded) {
+        return Err(Refusal::MixedLayoutRequired);
+    }
+    let same_performer =
+        matches!(destination, Destination::Performer(id) if scope.uniform == Uniform::Assigned(id));
+    let mut expected = p.clone();
+    let mut commands = Vec::new();
+    let mut deleted = BTreeSet::new();
+    if destination != Destination::LayoutOnly && !same_performer {
+        for (work, leaf) in &scope.leaves {
+            match destination {
+                Destination::Performer(performer) => {
+                    if let Some(existing) = &leaf.direct {
+                        if existing.source() != performer {
+                            let mut edited = existing.clone();
+                            edited.body = RelationBody::Allocation {
+                                source: performer,
+                                target: *work,
+                            };
+                            expected.relations.insert(edited.id, edited.clone());
+                            commands.push(Command::EditRelation(edited.id, edited));
+                        }
+                    } else {
+                        let id = *allocation_ids
+                            .get(work)
+                            .ok_or(Refusal::MissingAllocationId(*work))?;
+                        if id.is_nil() || expected.contains(id) {
+                            return Err(Refusal::InvalidCandidate(
+                                "The gesture's allocation identity is already in use.".into(),
+                            ));
+                        }
+                        let name = format!("{} performs {}", p.named(performer), p.named(*work));
+                        let relation = Relation {
+                            id,
+                            alias: expected.fresh_alias(&name, "allocation", id),
+                            name,
+                            description: String::new(),
+                            body: RelationBody::Allocation {
+                                source: performer,
+                                target: *work,
+                            },
+                        };
+                        expected.relations.insert(id, relation.clone());
+                        commands.push(Command::CreateRelation(relation));
+                    }
+                }
+                Destination::OutsidePerformers => {
+                    if !leaf.role_assignments.is_empty() {
+                        let roles: Vec<_> = leaf
+                            .role_assignments
+                            .iter()
+                            .map(Relation::source)
+                            .collect::<BTreeSet<_>>()
+                            .into_iter()
+                            .collect();
+                        let performers: Vec<_> = leaf
+                            .role_realizations
+                            .iter()
+                            .map(Relation::source)
+                            .collect::<BTreeSet<_>>()
+                            .into_iter()
+                            .collect();
+                        let message = if leaf.direct.is_some() && performers.len() == 1 {
+                            format!(
+                                "Removing direct assignment would place {} in {} through its role.",
+                                p.named(*work),
+                                p.named(performers[0])
+                            )
+                        } else {
+                            format!(
+                                "{} retains role responsibility through {}{}; edit that responsibility before moving outside performers.",
+                                p.named(*work),
+                                roles
+                                    .iter()
+                                    .map(|id| p.named(*id))
+                                    .collect::<Vec<_>>()
+                                    .join(", "),
+                                if performers.is_empty() {
+                                    String::new()
+                                } else {
+                                    format!(
+                                        " ({})",
+                                        performers
+                                            .iter()
+                                            .map(|id| p.named(*id))
+                                            .collect::<Vec<_>>()
+                                            .join(", ")
+                                    )
+                                }
+                            )
+                        };
+                        return Err(Refusal::RoleExitRequired {
+                            work: *work,
+                            roles,
+                            performers,
+                            message,
+                        });
+                    }
+                    if let Some(existing) = &leaf.direct {
+                        expected.relations.remove(&existing.id);
+                        deleted.insert(existing.id);
+                        commands.push(Command::Delete(existing.id));
+                    }
+                }
+                Destination::LayoutOnly => unreachable!(),
+            }
+        }
+    }
+    // A route cannot survive the intentional deletion of its own edge, even in
+    // another diagram. No other saved-view cleanup is authorized by this drag.
+    for diagram in expected.diagrams.values_mut() {
+        diagram.routes.retain(|r| !deleted.contains(&r.edge));
+    }
+    let actual = prepare_command(p, &Command::Batch(commands.clone()))
+        .map_err(|e| Refusal::InvalidCandidate(e.to_string()))?
+        .project;
+    exact_project(&expected, &actual)?;
+    let retained_roles = scope
+        .leaves
+        .values()
+        .any(|l| !l.role_assignments.is_empty());
+    let label = match destination {
+        Destination::LayoutOnly => "Arrange only".into(),
+        Destination::Performer(id) if same_performer => format!("Arrange within {}", p.named(id)),
+        Destination::Performer(id) => format!(
+            "Assign {} leaf {} to {}{}",
+            scope.leaves.len(),
+            match (scope.diagram.layer, scope.leaves.len()) {
+                (Layer::Oa, 1) => "activity",
+                (Layer::Oa, _) => "activities",
+                (Layer::Sa, 1) => "function",
+                (Layer::Sa, _) => "functions",
+            },
+            p.named(id),
+            if retained_roles {
+                " — explicit assignment; role responsibility retained"
+            } else {
+                ""
+            }
+        ),
+        Destination::OutsidePerformers if commands.is_empty() => {
+            "Arrange unassigned work — decomposition retained".into()
+        }
+        Destination::OutsidePerformers => "Remove assignment — decomposition retained".into(),
+    };
+    let warnings = validation::validate(&actual)
+        .into_iter()
+        .filter(|i| i.severity == Severity::Warning)
+        .collect();
+    let index = ViewIndex::new(&actual);
+    Ok(SemanticPlan {
+        scope: scope.clone(),
+        destination,
+        label,
+        warnings,
+        accepted: p.clone(),
+        candidate: actual,
+        index,
+        commands,
+        before_visible,
+        before_expanded,
+    })
+}
+
+/// World-space rectangle in the gesture's frozen transform. The UI resolver
+/// owns half-open pointer hits, semantic target precedence and occlusion.
+#[derive(Debug, Clone, Copy, PartialEq)]
+pub struct Rect {
+    pub position: Position,
+    pub size: Size,
+}
+
+impl Rect {
+    fn valid(self) -> bool {
+        [
+            self.position.x,
+            self.position.y,
+            self.size.width,
+            self.size.height,
+        ]
+        .iter()
+        .all(|n| n.is_finite() && n.abs() <= MAX_COORDINATE)
+            && self.size.width > 0.
+            && self.size.height > 0.
+    }
+    fn contains(self, other: Self) -> bool {
+        other.position.x >= self.position.x
+            && other.position.y >= self.position.y
+            && other.position.x + other.size.width <= self.position.x + self.size.width
+            && other.position.y + other.size.height <= self.position.y + self.size.height
+    }
+}
+
+#[derive(Debug, Clone, Copy, PartialEq)]
+pub struct TargetPresentation {
+    pub placement: Id,
+}
+
+#[derive(Debug, Clone, Copy, PartialEq)]
+pub struct PresentationContext {
+    /// Visible world rectangle derived from the actual captured pan/zoom/bounds.
+    pub viewport: Rect,
+    pub zoom: f32,
+    pub target: Option<TargetPresentation>,
+}
+
+#[derive(Debug)]
+pub struct PlacementPlan {
+    pub diagram: Diagram,
+    pub view: ProjectedView,
+    pub delta: Position,
+    pub unfolded: Option<Id>,
+    requested: Position,
+    presentation: PresentationContext,
+    commands: Vec<Command>,
+}
+
+/// `requested` is the original selected placement position plus pointer motion
+/// in the frozen transform (therefore preserving the press offset). Snap only
+/// this root; apply the resulting identical delta to captured Q and its routes.
+/// No whole Project clone, validator or semantic ViewIndex rebuild occurs here.
+pub fn place(
+    plan: &SemanticPlan,
+    requested: Position,
+    presentation: PresentationContext,
+) -> Result<PlacementPlan, Refusal> {
+    if !requested.x.is_finite()
+        || !requested.y.is_finite()
+        || !presentation.viewport.valid()
+        || !presentation.zoom.is_finite()
+        || presentation.zoom <= 0.
+    {
+        return Err(Refusal::LayoutRequired(
+            "Make room or adjust the view, then drag again.".into(),
+        ));
+    }
+    let root = &plan.scope.placements[&plan.scope.placement];
+    let delta = Position {
+        x: (requested.x / 10.).round() * 10. - root.position.x,
+        y: (requested.y / 10.).round() * 10. - root.position.y,
+    };
+    let mut diagram = plan.candidate.diagrams[&plan.scope.diagram.id].clone();
+    let mut commands = Vec::new();
+    let mut deltas = BTreeMap::new();
+    for (id, original) in &plan.scope.placements {
+        let node = diagram.nodes.get_mut(id).ok_or(Refusal::StaleScope)?;
+        node.position = Position {
+            x: original.position.x + delta.x,
+            y: original.position.y + delta.y,
+        };
+        if !(Rect {
+            position: node.position,
+            size: node.size,
+        })
+        .valid()
+        {
+            return Err(Refusal::InvalidCandidate(
+                "Moved coordinates exceed the model bounds.".into(),
+            ));
+        }
+        deltas.insert(*id, delta);
+        if node != original {
+            commands.push(Command::EditNode {
+                diagram: diagram.id,
+                original: *id,
+                node: node.clone(),
+            });
+        }
+    }
+    // Resolve endpoints using the captured accepted semantics, not a newly
+    // regrouped descendant walk. Own-edge deletions were removed above already.
+    for route in projection::translated_routes(&plan.accepted, &plan.scope.diagram, &deltas) {
+        if let Some(existing) = diagram.routes.iter_mut().find(|r| r.edge == route.edge) {
+            if route.waypoints.iter().any(|p| {
+                !p.x.is_finite()
+                    || !p.y.is_finite()
+                    || p.x.abs() > MAX_COORDINATE
+                    || p.y.abs() > MAX_COORDINATE
+            }) {
+                return Err(Refusal::InvalidCandidate(
+                    "Moved route exceeds the model bounds.".into(),
+                ));
+            }
+            *existing = route.clone();
+            commands.push(Command::SetEdgeRoute {
+                diagram: diagram.id,
+                route,
+            });
+        }
+    }
+    let mut unfolded = None;
+    if let Destination::Performer(performer) = plan.destination {
+        let target = presentation.target.ok_or_else(|| {
+            Refusal::LayoutRequired("A visible accepted performer target is required.".into())
+        })?;
+        let node = diagram
+            .nodes
+            .get_mut(&target.placement)
+            .ok_or(Refusal::StaleScope)?;
+        let visible_target = plan
+            .before_visible
+            .nodes
+            .iter()
+            .any(|n| n.id == target.placement && n.element == performer);
+        if node.element != performer || !visible_target {
+            return Err(Refusal::LayoutRequired(
+                "Make room or adjust the view, then drag again.".into(),
+            ));
+        }
+        if node.collapsed && !plan.commands.is_empty() {
+            node.collapsed = false;
+            unfolded = Some(node.id);
+            commands.push(Command::EditNode {
+                diagram: diagram.id,
+                original: node.id,
+                node: node.clone(),
+            });
+        }
+    } else if presentation.target.is_some() {
+        return Err(Refusal::Ineligible(
+            "This layout/outside destination has no performer target.".into(),
+        ));
+    }
+    let view = projection::project_diagram_with_index(&plan.candidate, &diagram, &plan.index);
+    let expanded = expanded_view(&plan.candidate, &diagram, &plan.scope, &plan.index);
+    check_geometry(plan, &view, &expanded, delta)?;
+    let selected = view
+        .nodes
+        .iter()
+        .find(|n| n.id == plan.scope.placement)
+        .ok_or_else(|| {
+            Refusal::LayoutRequired("The selected work header would be hidden.".into())
+        })?;
+    let header = Rect {
+        position: selected.position,
+        size: Size {
+            width: selected.size.width,
+            height: selected.size.height.min(62.),
+        },
+    };
+    if !presentation.viewport.contains(header) {
+        return Err(Refusal::LayoutRequired(
+            "Make room or adjust the view, then drag again.".into(),
+        ));
+    }
+    // Destination identity lives in a fixed toolbar slot. Frozen hit geometry
+    // and its outline never introduce an opaque label over this work header.
+    Ok(PlacementPlan {
+        diagram,
+        view,
+        delta,
+        unfolded,
+        requested,
+        presentation,
+        commands,
+    })
+}
+
+/// Final semantic/presentation equality gate, after the App has checked its
+/// current token, owner, revision, clean drafts, frozen target and transform.
+/// Recompute geometry to avoid accepting a modified/stale placement result.
+/// None means a snapped no-op: the caller must not execute or add history.
+pub fn finish(
+    plan: &SemanticPlan,
+    live: &Project,
+    placement: &PlacementPlan,
+) -> Result<Option<Command>, Refusal> {
+    if live != &plan.accepted {
+        return Err(Refusal::StaleScope);
+    }
+    let checked = place(plan, placement.requested, placement.presentation)?;
+    if checked.diagram != placement.diagram
+        || checked.view != placement.view
+        || checked.delta != placement.delta
+        || checked.unfolded != placement.unfolded
+        || checked.commands != placement.commands
+    {
+        return Err(Refusal::StaleScope);
+    }
+    let mut expected = plan.candidate.clone();
+    expected
+        .diagrams
+        .insert(checked.diagram.id, checked.diagram);
+    let mut commands = plan.commands.clone();
+    commands.extend(checked.commands);
+    let command = Command::Batch(commands);
+    let actual = prepare_command(live, &command)
+        .map_err(|e| Refusal::InvalidCandidate(e.to_string()))?
+        .project;
+    exact_project(&expected, &actual)?;
+    Ok((actual != *live).then_some(command))
+}
+
+fn expanded_view(
+    p: &Project,
+    diagram: &Diagram,
+    scope: &Scope,
+    index: &ViewIndex,
+) -> ProjectedView {
+    let mut expanded = diagram.clone();
+    for id in scope.placements.keys() {
+        if let Some(node) = expanded.nodes.get_mut(id) {
+            node.collapsed = false;
+        }
+    }
+    projection::project_diagram_with_index(p, &expanded, index)
+}
+
+fn ancestors(view: &ProjectedView) -> BTreeMap<Id, BTreeSet<Id>> {
+    let parents: BTreeMap<_, _> = view.nodes.iter().map(|n| (n.id, n.visual_parent)).collect();
+    parents
+        .keys()
+        .map(|node| {
+            let mut current = parents[node];
+            let mut seen = BTreeSet::new();
+            while let Some(id) = current {
+                if !seen.insert(id) {
+                    break;
+                }
+                current = parents.get(&id).copied().flatten();
+            }
+            (*node, seen)
+        })
+        .collect()
+}
+
+fn coherent(scope: &Scope, view: &ProjectedView) -> bool {
+    let ancestors = ancestors(view);
+    scope.placements.keys().all(|id| {
+        ancestors
+            .get(id)
+            .is_some_and(|parents| *id == scope.placement || parents.contains(&scope.placement))
+    })
+}
+
+fn overlap(a: &ProjectedNode, b: &ProjectedNode) -> f32 {
+    let width = (a.position.x + a.size.width).min(b.position.x + b.size.width)
+        - a.position.x.max(b.position.x);
+    let height = (a.position.y + a.size.height).min(b.position.y + b.size.height)
+        - a.position.y.max(b.position.y);
+    width.max(0.) * height.max(0.)
+}
+
+fn overlaps(before: &ProjectedView, after: &ProjectedView) -> bool {
+    // Build geometry ancestry once, avoiding a repeated descendant walk for
+    // every pair during pointer motion. Pairwise collision checking is bounded
+    // to these two projected scenes and does not traverse/clone model semantics.
+    let before_ancestors = ancestors(before);
+    let after_ancestors = ancestors(after);
+    let prior_nodes: BTreeMap<_, _> = before.nodes.iter().map(|n| (n.id, n)).collect();
+    for (i, a) in after.nodes.iter().enumerate() {
+        for b in &after.nodes[i + 1..] {
+            if after_ancestors[&a.id].contains(&b.id) || after_ancestors[&b.id].contains(&a.id) {
+                continue;
+            }
+            let prior = match (prior_nodes.get(&a.id), prior_nodes.get(&b.id)) {
+                (Some(x), Some(y))
+                    if !before_ancestors[&x.id].contains(&y.id)
+                        && !before_ancestors[&y.id].contains(&x.id) =>
+                {
+                    overlap(x, y)
+                }
+                _ => 0.,
+            };
+            if overlap(a, b) > prior + 0.01 {
+                return true;
+            }
+        }
+    }
+    false
+}
+
+fn check_geometry(
+    plan: &SemanticPlan,
+    visible: &ProjectedView,
+    expanded: &ProjectedView,
+    delta: Position,
+) -> Result<(), Refusal> {
+    if visible.nodes.iter().chain(&expanded.nodes).any(|n| {
+        !(Rect {
+            position: n.position,
+            size: n.size,
+        })
+        .valid()
+    }) {
+        return Err(Refusal::InvalidCandidate(
+            "The projected enclosure exceeds the model bounds.".into(),
+        ));
+    }
+    if plan.scope.work_records.len() > 1 {
+        if !coherent(&plan.scope, expanded) {
+            return Err(Refusal::MixedLayoutRequired);
+        }
+        for id in plan.scope.placements.keys() {
+            let old = plan
+                .before_expanded
+                .nodes
+                .iter()
+                .find(|n| n.id == *id)
+                .ok_or(Refusal::MixedLayoutRequired)?;
+            let new = expanded
+                .nodes
+                .iter()
+                .find(|n| n.id == *id)
+                .ok_or(Refusal::MixedLayoutRequired)?;
+            if (new.position.x - old.position.x - delta.x).abs() > 0.01
+                || (new.position.y - old.position.y - delta.y).abs() > 0.01
+                || (new.size.width - old.size.width).abs() > 0.01
+                || (new.size.height - old.size.height).abs() > 0.01
+            {
+                return Err(Refusal::LayoutRequired("This work subtree requires an explicit layout; its footprint cannot be translated unchanged.".into()));
+            }
+        }
+    }
+    if overlaps(&plan.before_visible, visible) || overlaps(&plan.before_expanded, expanded) {
+        return Err(Refusal::LayoutRequired("Make room before moving work: the candidate would introduce or enlarge overlapping cards.".into()));
+    }
+    Ok(())
+}
+
+/// Compare complete records, not just removed IDs. Deleting an Allocation can
+/// rewrite a surviving Constraint, remove artifacts/traces or prune view options.
+fn exact_project(expected: &Project, actual: &Project) -> Result<(), Refusal> {
+    if expected == actual {
+        return Ok(());
+    }
+    let mut records = Vec::new();
+    fn changes<T: PartialEq>(
+        expected: &BTreeMap<Id, T>,
+        actual: &BTreeMap<Id, T>,
+        category: &'static str,
+        project: &Project,
+        other: &Project,
+        records: &mut Vec<ChangedRecord>,
+    ) {
+        let ids: BTreeSet<_> = expected.keys().chain(actual.keys()).copied().collect();
+        for id in ids {
+            if expected.get(&id) != actual.get(&id) {
+                records.push(ChangedRecord {
+                    id,
+                    name: if project.contains(id) {
+                        project.named(id)
+                    } else {
+                        other.named(id)
+                    }
+                    .into(),
+                    category,
+                });
+            }
+        }
+    }
+    changes(
+        &expected.elements,
+        &actual.elements,
+        "element",
+        expected,
+        actual,
+        &mut records,
+    );
+    changes(
+        &expected.relations,
+        &actual.relations,
+        "relation",
+        expected,
+        actual,
+        &mut records,
+    );
+    changes(
+        &expected.diagrams,
+        &actual.diagrams,
+        "diagram",
+        expected,
+        actual,
+        &mut records,
+    );
+    changes(
+        &expected.artifact_links,
+        &actual.artifact_links,
+        "artifact",
+        expected,
+        actual,
+        &mut records,
+    );
+    changes(
+        &expected.traces,
+        &actual.traces,
+        "trace",
+        expected,
+        actual,
+        &mut records,
+    );
+    if expected.schema_version != actual.schema_version
+        || expected.id != actual.id
+        || expected.alias != actual.alias
+        || expected.name != actual.name
+        || expected.description != actual.description
+    {
+        records.push(ChangedRecord {
+            id: expected.id,
+            name: expected.name.clone(),
+            category: "project",
+        });
+    }
+    Err(Refusal::CollateralChangeRequired(records))
+}
+
+#[cfg(test)]
+mod tests;

crates/oa-desktop/src/allocation_input.rs

@@ -0,0 +1,268 @@
+//! A narrow dispatch boundary for Allocation work gestures. Iced rows visit
+//! siblings after capture; refusing inside Canvas alone still blurs an inspector
+//! field. Refuse before dispatching that press to any ordinary child instead.
+use crate::{
+    app::{
+        App, Message,
+        allocation_drag::{self, Event as WorkEvent},
+    },
+    diagram::DiagramCanvas,
+};
+use iced::advanced::{
+    Clipboard, Layout, Shell, Widget, layout, overlay, renderer,
+    widget::{Id, Operation, Tree, tree},
+};
+use iced::{
+    Element, Event, Length, Point, Rectangle, Renderer, Size, Theme, Vector, keyboard, mouse,
+};
+
+pub const CANVAS_ID: &str = "allocation-work-canvas";
+pub const ARRANGE_SHORTCUT: &str = "Alt+A";
+
+struct Root<'a> {
+    app: &'a App,
+    content: Element<'a, Message>,
+}
+#[derive(Default)]
+struct State {
+    pointer: Option<Point>,
+    refused_left: bool,
+}
+#[derive(Default)]
+struct CanvasBounds(Option<Rectangle>);
+impl Operation for CanvasBounds {
+    fn traverse(&mut self, visit: &mut dyn FnMut(&mut dyn Operation)) {
+        visit(self);
+    }
+    fn container(&mut self, id: Option<&Id>, bounds: Rectangle) {
+        if id == Some(&Id::new(CANVAS_ID)) {
+            self.0 = Some(bounds);
+        }
+    }
+}
+pub fn root<'a>(app: &'a App, content: impl Into<Element<'a, Message>>) -> Element<'a, Message> {
+    Element::new(Root {
+        app,
+        content: content.into(),
+    })
+}
+fn arrange_key(event: &Event) -> bool {
+    matches!(event, Event::Keyboard(keyboard::Event::KeyPressed {
+        key: keyboard::Key::Character(key), modifiers, repeat: false, ..
+    }) if key.eq_ignore_ascii_case("a") && *modifiers == keyboard::Modifiers::ALT)
+}
+impl Root<'_> {
+    fn dirty_object(&self, bounds: Rectangle, screen: Point) -> bool {
+        let Some(diagram) = self.app.active_diagram else {
+            return false;
+        };
+        if !allocation_drag::contains(bounds, screen) {
+            return false;
+        }
+        let canvas = DiagramCanvas {
+            allocation: Some(self.app.allocation_capability()),
+            project: self.app.project(),
+            view_index: Some(self.app.document.view_index()),
+            diagram,
+            selected: self.app.selected,
+            navigation_focus: None,
+            zoom: self.app.zoom,
+            pan: self.app.pan,
+            context: self.app.route_context().unwrap(),
+            selected_bend: None,
+            selected_attachment: None,
+            editable: false,
+            placing: false,
+            connection: None,
+        };
+        canvas.work_dirty_point(bounds, screen)
+    }
+}
+impl Widget<Message, Theme, Renderer> for Root<'_> {
+    fn tag(&self) -> tree::Tag {
+        tree::Tag::of::<State>()
+    }
+    fn state(&self) -> tree::State {
+        tree::State::new(State::default())
+    }
+    fn children(&self) -> Vec<Tree> {
+        vec![Tree::new(self.content.as_widget())]
+    }
+    fn diff(&self, tree: &mut Tree) {
+        tree.diff_children(std::slice::from_ref(&self.content));
+    }
+    fn size(&self) -> Size<Length> {
+        self.content.as_widget().size()
+    }
+    fn layout(
+        &mut self,
+        tree: &mut Tree,
+        renderer: &Renderer,
+        limits: &layout::Limits,
+    ) -> layout::Node {
+        self.content
+            .as_widget_mut()
+            .layout(&mut tree.children[0], renderer, limits)
+    }
+    fn operate(
+        &mut self,
+        tree: &mut Tree,
+        layout: Layout<'_>,
+        renderer: &Renderer,
+        operation: &mut dyn Operation,
+    ) {
+        self.content
+            .as_widget_mut()
+            .operate(&mut tree.children[0], layout, renderer, operation);
+    }
+    fn update(
+        &mut self,
+        tree: &mut Tree,
+        event: &Event,
+        layout: Layout<'_>,
+        cursor: mouse::Cursor,
+        renderer: &Renderer,
+        clipboard: &mut dyn Clipboard,
+        shell: &mut Shell<'_, Message>,
+        viewport: &Rectangle,
+    ) {
+        let state = tree.state.downcast_mut::<State>();
+        match event {
+            Event::Mouse(mouse::Event::CursorMoved { position }) => state.pointer = Some(*position),
+            Event::Mouse(mouse::Event::CursorLeft) => state.pointer = None,
+            Event::Window(iced::window::Event::RedrawRequested(_)) => {
+                state.pointer = cursor.position()
+            }
+            Event::Window(iced::window::Event::Unfocused) => {
+                state.pointer = None;
+                state.refused_left = false;
+            }
+            _ => {}
+        }
+        if state.refused_left {
+            if matches!(
+                event,
+                Event::Mouse(mouse::Event::ButtonReleased(mouse::Button::Left))
+            ) {
+                state.refused_left = false;
+                shell.capture_event();
+                return;
+            }
+            if matches!(event, Event::Mouse(mouse::Event::CursorMoved { .. })) {
+                shell.capture_event();
+                return;
+            }
+        }
+        if self.app.allocation_input_owner() && !shell.is_event_captured() {
+            if arrange_key(event) {
+                // App rechecks clean ownership before arming. A dirty field
+                // retains its actual widget focus and selection on refusal.
+                shell.publish(Message::WorkDrag(WorkEvent::ArrangeNext));
+                shell.capture_event();
+                return;
+            }
+            if self.app.allocation_drag.arrange_next
+                && matches!(
+                    event,
+                    Event::Keyboard(keyboard::Event::KeyPressed {
+                        key: keyboard::Key::Named(keyboard::key::Named::Escape),
+                        ..
+                    })
+                )
+            {
+                shell.publish(Message::Escape);
+                shell.capture_event();
+                return;
+            }
+            if !self.app.allocation_drag_clean()
+                && matches!(
+                    event,
+                    Event::Mouse(mouse::Event::ButtonPressed(mouse::Button::Left))
+                )
+                && let Some(screen) = state.pointer.or_else(|| cursor.position())
+            {
+                let mut canvas = CanvasBounds::default();
+                self.content.as_widget_mut().operate(
+                    &mut tree.children[0],
+                    layout,
+                    renderer,
+                    &mut canvas,
+                );
+                if canvas
+                    .0
+                    .is_some_and(|bounds| self.dirty_object(bounds, screen))
+                {
+                    state.refused_left = true;
+                    shell.publish(Message::WorkDrag(WorkEvent::Refused(
+                        self.app.allocation_drag.epoch,
+                        allocation_drag::FINISH_EDIT.into(),
+                    )));
+                    shell.capture_event();
+                    return;
+                }
+            }
+        }
+        self.content.as_widget_mut().update(
+            &mut tree.children[0],
+            event,
+            layout,
+            cursor,
+            renderer,
+            clipboard,
+            shell,
+            viewport,
+        );
+    }
+    fn draw(
+        &self,
+        tree: &Tree,
+        renderer: &mut Renderer,
+        theme: &Theme,
+        style: &renderer::Style,
+        layout: Layout<'_>,
+        cursor: mouse::Cursor,
+        viewport: &Rectangle,
+    ) {
+        self.content.as_widget().draw(
+            &tree.children[0],
+            renderer,
+            theme,
+            style,
+            layout,
+            cursor,
+            viewport,
+        );
+    }
+    fn mouse_interaction(
+        &self,
+        tree: &Tree,
+        layout: Layout<'_>,
+        cursor: mouse::Cursor,
+        viewport: &Rectangle,
+        renderer: &Renderer,
+    ) -> mouse::Interaction {
+        self.content.as_widget().mouse_interaction(
+            &tree.children[0],
+            layout,
+            cursor,
+            viewport,
+            renderer,
+        )
+    }
+    fn overlay<'b>(
+        &'b mut self,
+        tree: &'b mut Tree,
+        layout: Layout<'b>,
+        renderer: &Renderer,
+        viewport: &Rectangle,
+        translation: Vector,
+    ) -> Option<overlay::Element<'b, Message, Theme, Renderer>> {
+        self.content.as_widget_mut().overlay(
+            &mut tree.children[0],
+            layout,
+            renderer,
+            viewport,
+            translation,
+        )
+    }
+}

crates/oa-desktop/src/app/allocation_drag.rs

@@ -0,0 +1,672 @@
+//! Allocation work-body input admission. Gesture authority lives here, while
+//! the canvas retains ordered native pointer positions and frozen hit geometry.
+use super::{App, Message, Page};
+use crate::{allocation_drag as plan, route_edit::Context};
+use iced::{Point, Rectangle, Task, Vector};
+use oa_core::{projection::ProjectedView, routing::RoutedView, *};
+use std::{collections::BTreeMap, sync::Arc};
+
+pub const FINISH_EDIT: &str = "Finish or cancel the current edit before selecting or moving work.";
+
+#[derive(Debug, Clone, Copy, PartialEq)]
+pub struct Stamp {
+    pub context: Context,
+    pub epoch: u64,
+    pub snapshot: usize,
+    pub bounds: Rectangle,
+    pub pan: Vector,
+    pub zoom: f32,
+}
+impl Stamp {
+    pub fn world(self, screen: Point) -> Point {
+        Point::new(
+            (screen.x - self.bounds.x - self.pan.x) / self.zoom,
+            (screen.y - self.bounds.y - self.pan.y) / self.zoom,
+        )
+    }
+    pub fn viewport(self) -> plan::Rect {
+        let p = self.world(Point::new(self.bounds.x, self.bounds.y));
+        plan::Rect {
+            position: Position { x: p.x, y: p.y },
+            size: Size {
+                width: self.bounds.width / self.zoom,
+                height: self.bounds.height / self.zoom,
+            },
+        }
+    }
+}
+
+#[derive(Debug, Clone)]
+pub struct Target {
+    pub element: Id,
+    pub placement: Id,
+    pub region: Rectangle,
+    pub name: String,
+    pub ancestors: Vec<Id>,
+}
+#[derive(Debug, Clone)]
+pub struct Frozen {
+    pub targets: Vec<Target>,
+    cards: Vec<Rectangle>,
+    controls: Vec<Rectangle>,
+    edges: Vec<(Point, Point)>,
+    radius: f32,
+}
+#[derive(Debug, Clone, PartialEq)]
+pub enum Hit {
+    Destination(plan::Destination, Option<usize>),
+    OutsideViewport,
+    Occluded,
+    Ambiguous(Vec<usize>),
+}
+pub fn contains(r: Rectangle, p: Point) -> bool {
+    p.x >= r.x && p.y >= r.y && p.x < r.x + r.width && p.y < r.y + r.height
+}
+impl Frozen {
+    pub fn capture(
+        project: &Project,
+        scope: &plan::Scope,
+        view: &ProjectedView,
+        routed: &RoutedView,
+        zoom: f32,
+    ) -> Self {
+        let mut targets = Vec::new();
+        let mut cards = Vec::new();
+        for n in &view.nodes {
+            if scope.placements.contains_key(&n.id) {
+                continue;
+            }
+            let region = Rectangle::new(
+                Point::new(n.position.x, n.position.y),
+                iced::Size::new(n.size.width, n.size.height),
+            );
+            let Some(e) = project.elements.get(&n.element) else {
+                cards.push(region);
+                continue;
+            };
+            if e.kind().is_performer() && e.layer() == scope.diagram.layer {
+                let mut ancestors = Vec::new();
+                let mut parent = e.parent;
+                while let Some(id) = parent {
+                    if ancestors.contains(&id) {
+                        break;
+                    }
+                    ancestors.push(id);
+                    parent = project.elements.get(&id).and_then(|e| e.parent);
+                }
+                let name = project.named(e.id).to_owned();
+                let collapsed = scope.diagram.nodes[&n.id].collapsed;
+                targets.push(Target {
+                    element: e.id,
+                    placement: n.id,
+                    region: if collapsed {
+                        Rectangle {
+                            height: region.height.min(62.),
+                            ..region
+                        }
+                    } else {
+                        region
+                    },
+                    name,
+                    ancestors,
+                });
+            } else {
+                cards.push(region);
+            }
+        }
+        let radius = (10. / zoom).max(10.);
+        let mut controls: Vec<_> = view
+            .ports
+            .iter()
+            .filter(|port| !scope.placements.contains_key(&port.owner))
+            .map(|port| {
+                Rectangle::new(
+                    Point::new(port.position.x - radius, port.position.y - radius),
+                    iced::Size::new(radius * 2., radius * 2.),
+                )
+            })
+            .collect();
+        let mut edges = Vec::new();
+        for edge in routed.edges.values() {
+            if let Some(relation) = project.relations.get(&edge.id) {
+                for end in routing::association_end_geometry(relation, edge) {
+                    if !end.label.text.is_empty() {
+                        controls.push(Rectangle::new(
+                            Point::new(end.label.bounds.position.x, end.label.bounds.position.y),
+                            iced::Size::new(
+                                end.label.bounds.size.width,
+                                end.label.bounds.size.height,
+                            ),
+                        ));
+                    }
+                }
+            }
+            if !edge.label.text.is_empty() {
+                controls.push(Rectangle::new(
+                    Point::new(edge.label.bounds.position.x, edge.label.bounds.position.y),
+                    iced::Size::new(edge.label.bounds.size.width, edge.label.bounds.size.height),
+                ));
+            }
+            for pin in &edge.pins {
+                controls.push(Rectangle::new(
+                    Point::new(pin.x - 8. / zoom, pin.y - 8. / zoom),
+                    iced::Size::new(16. / zoom, 16. / zoom),
+                ));
+            }
+            for points in edge.points.windows(2) {
+                edges.push((
+                    Point::new(points[0].x, points[0].y),
+                    Point::new(points[1].x, points[1].y),
+                ));
+            }
+        }
+        Self {
+            targets,
+            cards,
+            controls,
+            edges,
+            radius: 6. / zoom,
+        }
+    }
+    pub fn resolve(&self, stamp: Stamp, screen: Option<Point>, arrange: bool) -> Hit {
+        let Some(screen) = screen.filter(|p| contains(stamp.bounds, *p)) else {
+            return Hit::OutsideViewport;
+        };
+        let p = stamp.world(screen);
+        // Drag status lives in the toolbar, outside this actual canvas viewport.
+        if self
+            .controls
+            .iter()
+            .chain(&self.cards)
+            .any(|r| contains(*r, p))
+            || self.edges.iter().any(|(a, b)| {
+                let d = *b - *a;
+                let length = d.x * d.x + d.y * d.y;
+                let t = if length == 0. {
+                    0.
+                } else {
+                    (((p.x - a.x) * d.x + (p.y - a.y) * d.y) / length).clamp(0., 1.)
+                };
+                p.distance(*a + d * t) <= self.radius
+            })
+        {
+            return Hit::Occluded;
+        }
+        if arrange {
+            return Hit::Destination(plan::Destination::LayoutOnly, None);
+        }
+        let hits: Vec<_> = self
+            .targets
+            .iter()
+            .enumerate()
+            .filter(|(_, t)| contains(t.region, p))
+            .map(|(i, _)| i)
+            .collect();
+        for (i, a) in hits.iter().enumerate() {
+            for b in &hits[i + 1..] {
+                let a = &self.targets[*a];
+                let b = &self.targets[*b];
+                if !a.ancestors.contains(&b.element) && !b.ancestors.contains(&a.element) {
+                    return Hit::Ambiguous(hits);
+                }
+            }
+        }
+        match hits
+            .into_iter()
+            .max_by_key(|i| self.targets[*i].ancestors.len())
+        {
+            Some(i) => Hit::Destination(
+                plan::Destination::Performer(self.targets[i].element),
+                Some(i),
+            ),
+            None => Hit::Destination(plan::Destination::OutsidePerformers, None),
+        }
+    }
+}
+
+#[derive(Debug, Clone)]
+pub struct Press {
+    pub stamp: Stamp,
+    pub token: Id,
+    pub start: Point,
+    pub scope: plan::Scope,
+    pub frozen: Frozen,
+    pub arrange: bool,
+}
+#[derive(Debug, Clone)]
+pub enum Event {
+    Press(Arc<Press>),
+    Preview(Stamp, Id, Option<Point>),
+    Release(Stamp, Id, Option<Point>),
+    Refused(u64, String),
+    Cancel(Id),
+    ArrangeNext,
+    Unfocused,
+    KeyboardBoundary,
+}
+pub struct Preview {
+    pub token: Id,
+    pub semantic: Arc<plan::SemanticPlan>,
+    pub placement: plan::PlacementPlan,
+    pub routed: Arc<RoutedView>,
+}
+struct Active {
+    press: Arc<Press>,
+    inspection_targets: Vec<usize>,
+    ids: BTreeMap<Id, Id>,
+    cache: Vec<(
+        plan::Destination,
+        Result<Arc<plan::SemanticPlan>, plan::Refusal>,
+    )>,
+}
+pub struct Feedback {
+    pub press: Arc<Press>,
+    pub targets: Vec<usize>,
+    /// Last captured target names for inspection only; never resolver input.
+    pub inspection_targets: Vec<usize>,
+    pub text: String,
+    pub refused: bool,
+}
+impl Feedback {
+    pub fn inspection_identity(&self) -> String {
+        if self.refused && self.targets.is_empty() && !self.inspection_targets.is_empty() {
+            let names = self
+                .inspection_targets
+                .iter()
+                .map(|index| self.press.frozen.targets[*index].name.as_str())
+                .collect::<Vec<_>>()
+                .join(" / ");
+            format!(
+                "{}\nLast target{}: {}\nReturn to the canvas to choose a destination; releasing here cancels the drag.",
+                self.destination_identity(),
+                if self.inspection_targets.len() > 1 {
+                    "s (ambiguous)"
+                } else {
+                    ""
+                },
+                names
+            )
+        } else {
+            self.destination_identity()
+        }
+    }
+    /// Captured accepted names, independent of clipped status/refusal prose.
+    pub fn destination_identity(&self) -> String {
+        match self.targets.as_slice() {
+            [] => if self.press.arrange {
+                "Arrange only"
+            } else if self.refused {
+                "No eligible destination"
+            } else {
+                "Outside performers"
+            }
+            .into(),
+            [index] => self.press.frozen.targets[*index].name.clone(),
+            indices => format!(
+                "Ambiguous: {}",
+                indices
+                    .iter()
+                    .map(|index| self.press.frozen.targets[*index].name.as_str())
+                    .collect::<Vec<_>>()
+                    .join(" / ")
+            ),
+        }
+    }
+}
+#[derive(Default)]
+pub struct State {
+    pub epoch: u64,
+    pub arrange_next: bool,
+    active: Option<Active>,
+    pub preview: Option<Arc<Preview>>,
+    pub feedback: Option<Feedback>,
+}
+#[derive(Clone, Copy)]
+pub struct Capability<'a> {
+    pub state: &'a State,
+    pub clean: bool,
+    pub snapshot: usize,
+}
+impl State {
+    fn retire(&mut self) {
+        self.epoch = self.epoch.wrapping_add(1);
+        self.active = None;
+        self.preview = None;
+        self.feedback = None;
+        self.arrange_next = false;
+    }
+}
+pub fn refusal(r: &plan::Refusal) -> String {
+    match r {
+        plan::Refusal::Ineligible(s) | plan::Refusal::InvalidCandidate(s) | plan::Refusal::LayoutRequired(s) => s.clone(),
+        plan::Refusal::StaleScope => "The view changed. Start this drag again.".into(),
+        plan::Refusal::MixedLayoutRequired => "This work has a distributed or mixed assignment. Drag a specific leaf; arranging this group needs a layout step.".into(),
+        plan::Refusal::RoleExitRequired { message, .. } => message.clone(),
+        plan::Refusal::MissingAllocationId(_) => "Assignment identity expired. Start this drag again.".into(),
+        plan::Refusal::CollateralChangeRequired(records) => format!(
+            "Assignment needs dependent edits to {}. Resolve these before dragging again.",
+            records.iter().map(|r| r.name.as_str()).collect::<Vec<_>>().join(", ")
+        ),
+    }
+}
+impl App {
+    pub fn allocation_drag_clean(&self) -> bool {
+        self.allocation_input_owner()
+            && !self.draft_dirty()
+            && !self.source_dirty()
+            && !self.behavior.has_pending()
+    }
+    pub(crate) fn allocation_input_owner(&self) -> bool {
+        self.page == Page::Diagram
+            && self
+                .active_diagram
+                .and_then(|id| self.project().diagrams.get(&id))
+                .is_some_and(|d| d.projection == ProjectionKind::Allocation)
+            && self.architecture.is_none()
+            && self.connection.is_none()
+            && self.model_menu.is_none()
+            && !self.reference_input_active()
+            && !self.busy
+            && !self.hosted.visible
+            && self.workflow.is_none()
+            && self.pending.is_none()
+            && self.file_prompt.is_none()
+            && !self.delete_pending
+            && self.diagram_usages.is_none()
+    }
+    pub fn allocation_capability(&self) -> Capability<'_> {
+        Capability {
+            state: &self.allocation_drag,
+            clean: self.allocation_drag_clean(),
+            snapshot: Arc::as_ptr(&self.document.snapshot()) as usize,
+        }
+    }
+    fn allocation_stamp_valid(&self, stamp: Stamp) -> bool {
+        self.allocation_drag_clean()
+            && self.route_context() == Some(stamp.context)
+            && self.allocation_drag.epoch == stamp.epoch
+            && Arc::as_ptr(&self.document.snapshot()) as usize == stamp.snapshot
+            && self.pan == stamp.pan
+            && self.zoom == stamp.zoom
+            && self.canvas_size.is_none_or(|s| s == stamp.bounds.size())
+            && stamp.bounds.width > 0.
+            && stamp.bounds.height > 0.
+    }
+    /// Called before general input dispatch. Even equal-valued actions (Fit,
+    /// Undo/Redo, tool/modal round trips) retire old render-time capabilities.
+    pub(super) fn allocation_before(&mut self, message: &Message) {
+        if !matches!(
+            message,
+            Message::WorkDrag(_)
+                | Message::CheckpointTick
+                | Message::CheckpointWritten(..)
+                | Message::Lint(_)
+                | Message::Linted(..)
+                | Message::CanvasResized(_)
+                | Message::WindowResized(_)
+                | Message::SourceViewport(_)
+                | Message::SourceSymbolsReady(_)
+                | Message::SourceRenameReady(_)
+                | Message::DiagramUsagesReady(_)
+                | Message::DiagramRevealViewport(..)
+        ) {
+            self.allocation_drag.retire();
+        }
+    }
+    pub(super) fn allocation_boundary(&self) -> impl PartialEq + use<> {
+        (
+            self.route_context(),
+            self.pan,
+            self.zoom,
+            self.canvas_size,
+            self.window_size,
+            self.allocation_drag_clean(),
+            Arc::as_ptr(&self.document.snapshot()) as usize,
+        )
+    }
+    pub(super) fn allocation_retire(&mut self) {
+        self.allocation_drag.retire();
+    }
+    fn select_work_clean(&mut self, press: &Press) -> bool {
+        if !self.allocation_stamp_valid(press.stamp) {
+            return false;
+        }
+        self.selected = press.scope.work;
+        self.selected_node = Some(press.scope.placement);
+        self.selected_bend = None;
+        self.refresh_draft();
+        true
+    }
+    pub(super) fn allocation_press_owns_current_view(&self, press: &Press) -> bool {
+        self.allocation_drag.active.is_none()
+            && self.allocation_stamp_valid(press.stamp)
+            && press.arrange == self.allocation_drag.arrange_next
+    }
+    pub(super) fn allocation_event_envelope(&self, event: &Event) -> bool {
+        match event {
+            Event::Cancel(token) | Event::Preview(_, token, _) | Event::Release(_, token, _) => {
+                self.allocation_drag
+                    .active
+                    .as_ref()
+                    .is_some_and(|active| active.press.token == *token)
+            }
+            Event::Refused(epoch, _) => *epoch == self.allocation_drag.epoch,
+            // Invalid Press packets deliberately report why the view or draft
+            // changed. Leave their existing validation and feedback intact.
+            _ => true,
+        }
+    }
+    pub(super) fn allocation_event(&mut self, event: Event) -> Task<Message> {
+        if !self.allocation_event_envelope(&event) {
+            return Task::none();
+        }
+        match event {
+            Event::ArrangeNext => {
+                self.allocation_drag.retire();
+                if self.allocation_drag_clean() {
+                    self.allocation_drag.arrange_next = true;
+                    self.status = "Arrange next drag armed · moves work only · Esc cancels".into();
+                } else {
+                    self.status = FINISH_EDIT.into();
+                }
+            }
+            Event::Unfocused => self.allocation_drag.retire(),
+            Event::KeyboardBoundary => {
+                if self.allocation_drag.active.is_some() {
+                    self.allocation_drag.retire();
+                }
+            }
+            Event::Cancel(token) => {
+                if self
+                    .allocation_drag
+                    .active
+                    .as_ref()
+                    .is_some_and(|a| a.press.token == token)
+                {
+                    self.allocation_drag.retire();
+                    self.status = "Work drag canceled".into();
+                }
+            }
+            Event::Refused(epoch, text) => {
+                if epoch == self.allocation_drag.epoch {
+                    self.allocation_drag.retire();
+                    self.status = text;
+                }
+            }
+            Event::Press(press) => {
+                if self.allocation_drag.active.is_some() {
+                    return Task::none();
+                }
+                if !self.allocation_press_owns_current_view(&press) {
+                    self.status = if self.allocation_drag_clean() {
+                        "The view changed. Start this drag again.".into()
+                    } else {
+                        FINISH_EDIT.into()
+                    };
+                    return Task::none();
+                }
+                let checked = plan::capture(
+                    self.project(),
+                    press.scope.diagram.id,
+                    press.scope.work,
+                    press.scope.placement,
+                );
+                if checked.as_ref() != Ok(&press.scope) || !self.select_work_clean(&press) {
+                    self.status = checked
+                        .err()
+                        .as_ref()
+                        .map(refusal)
+                        .unwrap_or_else(|| "The view changed. Start this drag again.".into());
+                    self.allocation_drag.retire();
+                    return Task::none();
+                }
+                let ids = press
+                    .scope
+                    .leaves
+                    .keys()
+                    .map(|id| (*id, Id::new_v4()))
+                    .collect();
+                self.allocation_drag.arrange_next = false;
+                self.allocation_drag.preview = None;
+                self.allocation_drag.feedback = None;
+                self.allocation_drag.active = Some(Active {
+                    press,
+                    inspection_targets: Vec::new(),
+                    ids,
+                    cache: Vec::new(),
+                });
+            }
+            Event::Preview(stamp, token, pointer) => {
+                self.allocation_motion(stamp, token, pointer, false)
+            }
+            Event::Release(stamp, token, pointer) => {
+                self.allocation_motion(stamp, token, pointer, true)
+            }
+        }
+        Task::none()
+    }
+    fn allocation_motion(
+        &mut self,
+        stamp: Stamp,
+        token: Id,
+        pointer: Option<Point>,
+        release: bool,
+    ) {
+        if self
+            .allocation_drag
+            .active
+            .as_ref()
+            .is_none_or(|a| a.press.token != token)
+        {
+            return; // An old packet cannot cancel a newer gesture.
+        }
+        if !self.allocation_stamp_valid(stamp) {
+            self.allocation_drag.retire();
+            self.status = if self.allocation_drag_clean() {
+                "The view changed. Start this drag again.".into()
+            } else {
+                FINISH_EDIT.into()
+            };
+            return;
+        }
+        let Some(mut active) = self.allocation_drag.active.take() else {
+            return;
+        };
+        if active.press.token != token || active.press.stamp != stamp {
+            self.allocation_drag.active = Some(active);
+            return;
+        }
+        let press = active.press.clone();
+        let moved = pointer.is_some_and(|p| p.distance(press.start) > 3.);
+        let hit = press.frozen.resolve(stamp, pointer, press.arrange);
+        if moved {
+            match &hit {
+                Hit::Destination(_, Some(target)) => active.inspection_targets = vec![*target],
+                Hit::Ambiguous(targets) => active.inspection_targets = targets.clone(),
+                _ => {}
+            }
+        }
+        let mut targets = Vec::new();
+        let mut preview = None;
+        let result: Result<String, String> = match hit {
+            Hit::OutsideViewport => Err(if release {
+                "Work drag canceled outside the canvas."
+            } else {
+                "Pointer outside canvas · return to choose a destination; releasing here cancels the drag."
+            }.into()),
+            _ if !moved => Ok("Work selected".into()),
+            Hit::Occluded => Err("Aim at exposed performer space or empty canvas; this card, port, connection or control blocks the drop.".into()),
+            Hit::Ambiguous(indices) => {
+                targets = indices;
+                Err("Two unrelated performers overlap here. Use an exposed region.".into())
+            }
+            Hit::Destination(destination, target) => {
+                targets.extend(target);
+                let semantic = if let Some((_, result)) = active.cache.iter().find(|(d, _)| *d == destination) {
+                    result.clone()
+                } else {
+                    let result = plan::plan_semantics(self.project(), &press.scope, destination, &active.ids).map(Arc::new);
+                    active.cache.push((destination, result.clone()));
+                    result
+                };
+                semantic.map_err(|r| refusal(&r)).and_then(|semantic| {
+                    if stamp.zoom * 16. < 9. {
+                        return Err("Make room or adjust the view, then drag again. Zoom in to read the work and destination.".into());
+                    }
+                    let pointer = pointer.unwrap();
+                    let delta = pointer - press.start;
+                    let original = press.scope.placements[&press.scope.placement].position;
+                    let requested = Position { x: original.x + delta.x / stamp.zoom, y: original.y + delta.y / stamp.zoom };
+                    let presentation = plan::PresentationContext {
+                        viewport: stamp.viewport(), zoom: stamp.zoom,
+                        target: target.map(|i| {
+                            let t = &press.frozen.targets[i];
+                            plan::TargetPresentation { placement: t.placement }
+                        }),
+                    };
+                    let placement = plan::place(&semantic, requested, presentation).map_err(|r| refusal(&r))?;
+                    let label = if semantic.warnings.is_empty() { semantic.label.clone() } else {
+                        format!("{} · {} model warning(s) retained", semantic.label, semantic.warnings.len())
+                    };
+                    if release {
+                        let command = plan::finish(&semantic, self.project(), &placement).map_err(|r| refusal(&r))?;
+                        if let Some(command) = command {
+                            // Bypass applying selectors and unrelated repair helpers. The
+                            // planner's exact Batch enters the authoritative source pipeline.
+                            self.document.execute(command).map_err(|e| format!("{} · retry this drag after correcting the source issue", e))?;
+                            self.sync();
+                            self.selected = press.scope.work;
+                            self.selected_node = Some(press.scope.placement);
+                            self.refresh_draft();
+                        }
+                    } else {
+                        let routed = Arc::new(routing::route_diagram(semantic.project(), &placement.diagram, &placement.view));
+                        preview = Some(Arc::new(Preview { token, semantic, placement, routed }));
+                    }
+                    Ok(label)
+                })
+            }
+        };
+        let refused = result.is_err();
+        let text = result.unwrap_or_else(|text| text);
+        self.status = text.clone();
+        if release {
+            self.allocation_drag.retire();
+        } else {
+            let inspection_targets = active.inspection_targets.clone();
+            self.allocation_drag.active = Some(active);
+            self.allocation_drag.preview = preview;
+            self.allocation_drag.feedback = Some(Feedback {
+                press,
+                targets,
+                inspection_targets,
+                text,
+                refused,
+            });
+        }
+    }
+}
+
+#[cfg(test)]
+#[path = "allocation_drag_tests.rs"]
+mod tests;

crates/oa-desktop/src/app/allocation_drag_full_tree_tests.rs

@@ -0,0 +1,728 @@
+//! Actual App root, retained Iced tree, property widgets and production renderer.
+//! Unlike packet-only tests, these prove the next key still reaches the field.
+use super::*;
+use crate::behavior::canvas_workspace::tests::{Mounted, key};
+use iced::{Event as Input, keyboard};
+
+fn character(text: &str, modifiers: keyboard::Modifiers) -> Input {
+    Input::Keyboard(keyboard::Event::KeyPressed {
+        key: keyboard::Key::Character(text.into()),
+        modified_key: keyboard::Key::Character(text.into()),
+        physical_key: keyboard::key::Physical::Code(keyboard::key::Code::KeyA),
+        location: keyboard::Location::Standard,
+        modifiers,
+        text: Some(text.into()),
+        repeat: false,
+    })
+}
+async fn mount() -> (Fixture, Mounted) {
+    let mut f = fixture(Layer::Oa);
+    f.app.window_size = iced::Size::new(2000., 1400.);
+    let _ = f.app.update(Message::Select(f.work));
+    let mut mounted = Mounted::new(&mut f.app).await;
+    // First sensor measurement intentionally Fits; now use a fixed known camera.
+    f.app.zoom = 1.;
+    f.app.pan = Vector::ZERO;
+    f.app.fit_to_view = false;
+    mounted.settle(&mut f.app).await;
+    (f, mounted)
+}
+fn canvas_bounds(mounted: &mut Mounted, app: &App) -> Rectangle {
+    mounted
+        .geometry(app)
+        .bounds(crate::allocation_input::CANVAS_ID)
+}
+fn at(mounted: &mut Mounted, f: &Fixture, world: Position) -> Point {
+    let bounds = canvas_bounds(mounted, &f.app);
+    Point::new(
+        bounds.x + world.x * f.app.zoom + f.app.pan.x,
+        bounds.y + world.y * f.app.zoom + f.app.pan.y,
+    )
+}
+fn name_field(mounted: &mut Mounted, app: &App) -> Rectangle {
+    mounted
+        .geometry(app)
+        .text_inputs
+        .into_iter()
+        .filter(|b| b.x > app.window_size.width - 320.)
+        .min_by(|a, b| a.y.total_cmp(&b.y))
+        .expect("actual inspector Name TextInput")
+}
+fn description_field(mounted: &mut Mounted, app: &App) -> Rectangle {
+    mounted
+        .geometry(app)
+        .focused
+        .into_iter()
+        .map(|(_, bounds, _)| bounds)
+        .filter(|b| b.x > app.window_size.width - 320. && b.height >= 90.)
+        .min_by(|a, b| a.y.total_cmp(&b.y))
+        .expect("actual inspector Description TextEditor")
+}
+fn is_focused(mounted: &mut Mounted, app: &App, field: Rectangle) -> bool {
+    mounted
+        .geometry(app)
+        .focused
+        .iter()
+        .any(|(_, bounds, focused)| *bounds == field && *focused)
+}
+async fn type_key(mounted: &mut Mounted, app: &mut App, text: &str) -> Vec<Message> {
+    mounted
+        .batch(
+            app,
+            &[character(text, keyboard::Modifiers::empty())],
+            mouse::Cursor::Unavailable,
+        )
+        .await
+}
+async fn refused_click_keeps_field(mounted: &mut Mounted, f: &mut Fixture, field: Rectangle) {
+    let before = f.app.document.bundle().clone();
+    let selected = (f.app.selected, f.app.selected_node);
+    let point = at(mounted, f, xy(140., 535.));
+    let messages = mounted.click(&mut f.app, point).await;
+    assert!(
+        messages
+            .iter()
+            .any(|m| matches!(m, Message::WorkDrag(Event::Refused(..))))
+    );
+    assert!(!messages.iter().any(|m| matches!(
+        m,
+        Message::Select(_) | Message::SelectNode(_) | Message::MoveNode(..)
+    )));
+    assert_eq!(f.app.document.bundle(), &before);
+    assert_eq!((f.app.selected, f.app.selected_node), selected);
+    assert!(
+        is_focused(mounted, &f.app, field),
+        "refused press must not reach the outside-press unfocus handler"
+    );
+}
+
+#[tokio::test]
+async fn actual_app_tree_dirty_name_retains_focus_and_middle_caret_for_next_key() {
+    let (mut f, mut mounted) = mount().await;
+    let field = name_field(&mut mounted, &f.app);
+    mounted.click(&mut f.app, field.center()).await;
+    mounted
+        .batch(
+            &mut f.app,
+            &[key(keyboard::key::Named::Home)],
+            mouse::Cursor::Unavailable,
+        )
+        .await;
+    type_key(&mut mounted, &mut f.app, "X").await;
+    mounted
+        .batch(
+            &mut f.app,
+            &[key(keyboard::key::Named::ArrowLeft)],
+            mouse::Cursor::Unavailable,
+        )
+        .await;
+    assert_eq!(f.app.draft.as_ref().unwrap().inputs["/name"].raw, "XWork");
+    refused_click_keeps_field(&mut mounted, &mut f, field).await;
+    let messages = type_key(&mut mounted, &mut f.app, "Y").await;
+    assert!(
+        messages
+            .iter()
+            .any(|m| matches!(m, Message::Field(path, _) if path == "/name"))
+    );
+    assert_eq!(f.app.draft.as_ref().unwrap().inputs["/name"].raw, "YXWork");
+    assert!(!f.app.document.can_undo());
+}
+
+#[tokio::test]
+async fn actual_app_tree_dirty_description_retains_focus_and_middle_caret_for_next_key() {
+    let (mut f, mut mounted) = mount().await;
+    let field = description_field(&mut mounted, &f.app);
+    mounted
+        .click(&mut f.app, Point::new(field.x + 16., field.y + 16.))
+        .await;
+    type_key(&mut mounted, &mut f.app, "A").await;
+    type_key(&mut mounted, &mut f.app, "B").await;
+    mounted
+        .batch(
+            &mut f.app,
+            &[key(keyboard::key::Named::ArrowLeft)],
+            mouse::Cursor::Unavailable,
+        )
+        .await;
+    assert_eq!(
+        f.app.draft.as_ref().unwrap().inputs["/description"].raw,
+        "AB"
+    );
+    refused_click_keeps_field(&mut mounted, &mut f, field).await;
+    let messages = type_key(&mut mounted, &mut f.app, "X").await;
+    assert!(
+        messages
+            .iter()
+            .any(|m| matches!(m, Message::FieldText(path, _) if path == "/description"))
+    );
+    assert_eq!(
+        f.app.draft.as_ref().unwrap().inputs["/description"].raw,
+        "AXB"
+    );
+    assert!(!f.app.document.can_undo());
+}
+
+#[tokio::test]
+async fn actual_keyboard_arrange_shortcut_consumes_once_escape_cancels_and_dirty_owner_refuses() {
+    let (mut f, mut mounted) = mount().await;
+    let shortcut = character("a", keyboard::Modifiers::ALT);
+    let messages = mounted
+        .batch(
+            &mut f.app,
+            std::slice::from_ref(&shortcut),
+            mouse::Cursor::Unavailable,
+        )
+        .await;
+    assert!(
+        messages
+            .iter()
+            .any(|m| matches!(m, Message::WorkDrag(Event::ArrangeNext)))
+    );
+    assert!(f.app.allocation_drag.arrange_next);
+    mounted
+        .batch(
+            &mut f.app,
+            &[key(keyboard::key::Named::Escape)],
+            mouse::Cursor::Unavailable,
+        )
+        .await;
+    assert!(!f.app.allocation_drag.arrange_next);
+    mounted
+        .batch(
+            &mut f.app,
+            std::slice::from_ref(&shortcut),
+            mouse::Cursor::Unavailable,
+        )
+        .await;
+    let from = at(&mut mounted, &f, xy(140., 535.));
+    let to = from + Vector::new(30., 0.);
+    let messages = mounted
+        .batch(
+            &mut f.app,
+            &[
+                Input::Mouse(mouse::Event::CursorMoved { position: from }),
+                Input::Mouse(mouse::Event::ButtonPressed(mouse::Button::Left)),
+                Input::Mouse(mouse::Event::CursorMoved { position: to }),
+                Input::Mouse(mouse::Event::ButtonReleased(mouse::Button::Left)),
+            ],
+            mouse::Cursor::Available(to),
+        )
+        .await;
+    assert!(
+        messages
+            .iter()
+            .any(|m| matches!(m, Message::WorkDrag(Event::Press(p)) if p.arrange))
+    );
+    assert!(!f.app.allocation_drag.arrange_next);
+    assert_eq!(f.app.document.revision(), 1, "{}", f.app.status);
+    assert!(f.app.project().relations.is_empty());
+    let field = name_field(&mut mounted, &f.app);
+    mounted.click(&mut f.app, field.center()).await;
+    type_key(&mut mounted, &mut f.app, "X").await;
+    let raw = f.app.draft.as_ref().unwrap().inputs["/name"].raw.clone();
+    let before = f.app.document.bundle().clone();
+    mounted
+        .batch(&mut f.app, &[shortcut], mouse::Cursor::Unavailable)
+        .await;
+    assert!(!f.app.allocation_drag.arrange_next);
+    assert_eq!(f.app.status, FINISH_EDIT);
+    assert!(is_focused(&mut mounted, &f.app, field));
+    assert_eq!(f.app.draft.as_ref().unwrap().inputs["/name"].raw, raw);
+    assert_eq!(f.app.document.bundle(), &before);
+}
+
+fn canvas_pixels(pixels: &[u8], width: usize, canvas: Rectangle) -> Vec<u8> {
+    let x = canvas.x.ceil() as usize;
+    let y = canvas.y.ceil() as usize;
+    let right = (canvas.x + canvas.width).floor() as usize;
+    let bottom = (canvas.y + canvas.height).floor() as usize;
+    (y..bottom)
+        .flat_map(|row| {
+            pixels[(row * width + x) * 4..(row * width + right) * 4]
+                .iter()
+                .copied()
+        })
+        .collect()
+}
+
+#[tokio::test]
+async fn actual_rendered_canvas_pixels_do_not_change_when_toolbar_feedback_text_changes() {
+    let (mut f, mut mounted) = mount().await;
+    let mut project = f.app.project().clone();
+    let target = project
+        .diagrams
+        .get_mut(&f.diagram)
+        .unwrap()
+        .nodes
+        .values_mut()
+        .find(|n| n.element == f.a)
+        .unwrap();
+    target.position.y = -41.;
+    target.size.height = 300.;
+    replace(&mut f, project);
+    f.app.zoom = 0.75;
+    f.app.pan = Vector::new(15., 15.);
+    let from = at(&mut mounted, &f, xy(140., 535.));
+    let to = at(&mut mounted, &f, xy(200., 80.));
+    mounted
+        .batch(
+            &mut f.app,
+            &[
+                Input::Mouse(mouse::Event::CursorMoved { position: from }),
+                Input::Mouse(mouse::Event::ButtonPressed(mouse::Button::Left)),
+                Input::Mouse(mouse::Event::CursorMoved { position: to }),
+            ],
+            mouse::Cursor::Available(to),
+        )
+        .await;
+    let feedback = f
+        .app
+        .allocation_drag
+        .feedback
+        .as_ref()
+        .expect("active frozen destination");
+    assert!(!feedback.refused, "{}", feedback.text);
+    let target = &feedback.press.frozen.targets[feedback.targets[0]];
+    assert!(target.region.y * f.app.zoom + f.app.pan.y < 0.);
+    assert_eq!(feedback.destination_identity(), "A");
+    let canvas = canvas_bounds(&mut mounted, &f.app);
+    let first = mounted.pixels(&f.app);
+    f.app.allocation_drag.feedback.as_mut().unwrap().text =
+        "Very different drag status, retained outside the readable canvas. ".repeat(10);
+    let second = mounted.pixels(&f.app);
+    assert_ne!(first, second, "the actual toolbar status changes");
+    assert_eq!(
+        canvas_pixels(&first, f.app.window_size.width as usize, canvas),
+        canvas_pixels(&second, f.app.window_size.width as usize, canvas),
+        "status must not obscure any candidate header or destination identity"
+    );
+}
+
+fn destination_bounds(mounted: &mut Mounted, app: &App) -> Rectangle {
+    mounted.geometry(app).bounds("allocation-destination")
+}
+fn assert_on_screen(bounds: Rectangle, app: &App) {
+    assert!(
+        bounds.x >= 0. && bounds.y >= 0. && bounds.width >= 400. && bounds.height == 26.,
+        "{bounds:?}"
+    );
+    assert!(
+        bounds.x + bounds.width <= app.window_size.width
+            && bounds.y + bounds.height <= app.window_size.height,
+        "{bounds:?}"
+    );
+}
+
+#[tokio::test]
+async fn actual_app_tree_exact_incoming_drag_keeps_destination_visible_and_canvas_stable() {
+    for layer in [Layer::Oa, Layer::Sa] {
+        for (minimum, name, collapsed, zoom, pan) in [
+            (false, "Receiver", false, 1., Vector::ZERO),
+            (false, "Receiver", false, 0.75, Vector::new(37., -15.)),
+            (
+                false,
+                "Receiving subsystem",
+                true,
+                1.25,
+                Vector::new(-30., 23.),
+            ),
+            (
+                false,
+                "Receiving subsystem",
+                true,
+                1.,
+                Vector::new(0., -100.),
+            ),
+            (true, "Receiving subsystem", true, 1., Vector::ZERO),
+            (
+                true,
+                "Receiving subsystem WWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWW",
+                true,
+                1.,
+                Vector::new(0., -100.),
+            ),
+        ] {
+            let mut f = fixture(layer);
+            let mut project = f.app.project().clone();
+            project.elements.get_mut(&f.a).unwrap().name = name.into();
+            let diagram = project.diagrams.get_mut(&f.diagram).unwrap();
+            let target = diagram
+                .nodes
+                .values_mut()
+                .find(|n| n.element == f.a)
+                .unwrap();
+            target.collapsed = collapsed;
+            let target_id = target.id;
+            // At minimum size, keep the source in the visible canvas; preserve
+            // the same standard (40,35) name grab and original target geometry.
+            let source_y = if minimum { 210. } else { 500. };
+            diagram.nodes.get_mut(&f.node).unwrap().position.y = source_y;
+            replace(&mut f, project);
+            f.app.layer = layer;
+            f.app.window_size = if minimum {
+                iced::Size::new(1100., 700.)
+            } else {
+                iced::Size::new(2000., 1400.)
+            };
+            let _ = f.app.update(Message::Select(f.work));
+            let mut mounted = Mounted::new(&mut f.app).await;
+            f.app.zoom = zoom;
+            f.app.pan = pan;
+            f.app.fit_to_view = false;
+            mounted.settle(&mut f.app).await;
+            let canvas = canvas_bounds(&mut mounted, &f.app);
+            let slot = destination_bounds(&mut mounted, &f.app);
+            assert_on_screen(slot, &f.app);
+            assert!(slot.y + slot.height <= canvas.y);
+            let idle = mounted.pixels(&f.app);
+            let before = f.app.project().clone();
+            let source = f.app.document.bundle().clone();
+            let from = at(&mut mounted, &f, xy(140., source_y + 35.));
+            // Use the middle of the snap cell. Fractional App-layout origins
+            // can perturb an exact half-grid tie by one floating-point ULP.
+            // The packet/planner cases retain the original y140 counterexample.
+            let to = at(&mut mounted, &f, xy(160., 145.));
+            assert!(
+                canvas.contains(from) && canvas.contains(to),
+                "{canvas:?} {from:?} {to:?}"
+            );
+            mounted
+                .batch(
+                    &mut f.app,
+                    &[
+                        Input::Mouse(mouse::Event::CursorMoved { position: from }),
+                        Input::Mouse(mouse::Event::ButtonPressed(mouse::Button::Left)),
+                        Input::Mouse(mouse::Event::CursorMoved { position: to }),
+                    ],
+                    mouse::Cursor::Available(to),
+                )
+                .await;
+            let feedback = f
+                .app
+                .allocation_drag
+                .feedback
+                .as_ref()
+                .expect(&f.app.status);
+            assert!(!feedback.refused, "{}", feedback.text);
+            assert_eq!(feedback.destination_identity(), name);
+            let preview = f.app.allocation_drag.preview.as_ref().expect(&f.app.status);
+            assert_eq!(
+                preview.placement.diagram.nodes[&f.node].position,
+                xy(120., 110.),
+                "{layer:?}, minimum={minimum}, zoom={zoom}, pan={pan:?}, canvas={canvas:?}"
+            );
+            assert!(!preview.placement.diagram.nodes[&target_id].collapsed);
+            let selected = preview
+                .placement
+                .view
+                .nodes
+                .iter()
+                .find(|node| node.id == f.node)
+                .unwrap();
+            let selected_header = Rectangle::new(
+                Point::new(
+                    canvas.x + selected.position.x * zoom + pan.x,
+                    canvas.y + selected.position.y * zoom + pan.y,
+                ),
+                iced::Size::new(
+                    selected.size.width * zoom,
+                    selected.size.height.min(62.) * zoom,
+                ),
+            );
+            assert!(canvas.contains(Point::new(selected_header.x, selected_header.y)));
+            assert!(
+                selected_header.x + selected_header.width <= canvas.x + canvas.width
+                    && selected_header.y + selected_header.height <= canvas.y + canvas.height
+            );
+            let mut expected = preview.semantic.project().clone();
+            expected
+                .diagrams
+                .insert(f.diagram, preview.placement.diagram.clone());
+            assert_eq!(f.app.project(), &before);
+            assert_eq!(f.app.document.bundle(), &source);
+            assert!(!f.app.document.can_undo());
+            assert_eq!(canvas_bounds(&mut mounted, &f.app), canvas);
+            assert_eq!(destination_bounds(&mut mounted, &f.app), slot);
+            let active = mounted.pixels(&f.app);
+            if minimum {
+                record_render_evidence(
+                    &format!(
+                        "{layer:?}-minimum-{}",
+                        if pan.y < 0. { "top" } else { "normal" }
+                    ),
+                    &active,
+                    &f.app,
+                    slot,
+                    canvas,
+                );
+            }
+            let width = f.app.window_size.width as usize;
+            assert_ne!(
+                canvas_pixels(&idle, width, slot),
+                canvas_pixels(&active, width, slot),
+                "actual destination text is painted in its dedicated visible slot"
+            );
+            f.app.allocation_drag.feedback.as_mut().unwrap().text =
+                "Long refusal/status prose must not obscure work or destination. ".repeat(30);
+            let verbose = mounted.pixels(&f.app);
+            assert_ne!(active, verbose);
+            assert_eq!(
+                canvas_pixels(&active, width, canvas),
+                canvas_pixels(&verbose, width, canvas)
+            );
+            assert_eq!(
+                canvas_pixels(&active, width, slot),
+                canvas_pixels(&verbose, width, slot)
+            );
+            assert_eq!(canvas_bounds(&mut mounted, &f.app), canvas);
+            if pan.y == -100. {
+                // A genuine clipping refusal in the same held gesture, then
+                // recovery at the original exact point: no camera rebasing.
+                let clipped = at(&mut mounted, &f, xy(160., 110.));
+                mounted
+                    .batch(
+                        &mut f.app,
+                        &[Input::Mouse(mouse::Event::CursorMoved {
+                            position: clipped,
+                        })],
+                        mouse::Cursor::Available(clipped),
+                    )
+                    .await;
+                assert!(f.app.allocation_drag.feedback.as_ref().unwrap().refused);
+                assert!(f.app.allocation_drag.preview.is_none());
+                assert_eq!(canvas_bounds(&mut mounted, &f.app), canvas);
+                assert_eq!(destination_bounds(&mut mounted, &f.app), slot);
+                assert_eq!(f.app.project(), &before);
+                assert_eq!(f.app.document.bundle(), &source);
+                mounted
+                    .batch(
+                        &mut f.app,
+                        &[Input::Mouse(mouse::Event::CursorMoved { position: to })],
+                        mouse::Cursor::Available(to),
+                    )
+                    .await;
+                assert!(!f.app.allocation_drag.feedback.as_ref().unwrap().refused);
+            }
+            mounted
+                .batch(
+                    &mut f.app,
+                    &[Input::Mouse(mouse::Event::ButtonReleased(
+                        mouse::Button::Left,
+                    ))],
+                    mouse::Cursor::Available(to),
+                )
+                .await;
+            assert_eq!(f.app.project(), &expected, "{}", f.app.status);
+            assert_eq!(f.app.document.revision(), 1);
+            assert_eq!(canvas_bounds(&mut mounted, &f.app), canvas);
+            assert_eq!(destination_bounds(&mut mounted, &f.app), slot);
+            let after = f.app.document.bundle().clone();
+            let _ = f.app.update(Message::Undo);
+            assert_eq!(f.app.project(), &before);
+            assert_eq!(f.app.document.bundle(), &source);
+            assert!(!f.app.document.can_undo());
+            let _ = f.app.update(Message::Redo);
+            assert_eq!(f.app.project(), &expected);
+            assert_eq!(f.app.document.bundle(), &after);
+            assert!(!f.app.document.can_redo());
+        }
+    }
+}
+
+/// Optional reproducible visual evidence; normal test runs create no artifacts.
+fn record_render_evidence(
+    name: &str,
+    pixels: &[u8],
+    app: &App,
+    slot: Rectangle,
+    canvas: Rectangle,
+) {
+    let Some(path) = std::env::var_os("ARCADIA_RENDER_EVIDENCE_DIR") else {
+        return;
+    };
+    let path = std::path::PathBuf::from(path);
+    std::fs::create_dir_all(&path).unwrap();
+    let mut file = std::fs::OpenOptions::new()
+        .write(true)
+        .create_new(true)
+        .open(path.join(format!("{name}.rgba")))
+        .unwrap();
+    std::io::Write::write_all(&mut file, pixels).unwrap();
+    let metadata = serde_json::json!({
+        "width": app.window_size.width as u32, "height": app.window_size.height as u32,
+        "destination": [slot.x, slot.y, slot.width, slot.height],
+        "canvas": [canvas.x, canvas.y, canvas.width, canvas.height],
+        "identity": app.allocation_drag.feedback.as_ref().map(|f| f.destination_identity()),
+    });
+    let mut file = std::fs::OpenOptions::new()
+        .write(true)
+        .create_new(true)
+        .open(path.join(format!("{name}.json")))
+        .unwrap();
+    std::io::Write::write_all(&mut file, &serde_json::to_vec_pretty(&metadata).unwrap()).unwrap();
+}
+
+#[tokio::test]
+async fn actual_toolbar_hover_inspects_last_full_name_without_authorizing_an_outside_drop() {
+    for layer in [Layer::Oa, Layer::Sa] {
+        let mut f = fixture(layer);
+        let name = "Receiving subsystem with a long exact identity beyond the compact label";
+        let mut project = f.app.project().clone();
+        project.elements.get_mut(&f.a).unwrap().name = name.into();
+        project
+            .diagrams
+            .get_mut(&f.diagram)
+            .unwrap()
+            .nodes
+            .get_mut(&f.node)
+            .unwrap()
+            .position
+            .y = 210.;
+        replace(&mut f, project);
+        f.app.layer = layer;
+        f.app.window_size = iced::Size::new(1100., 700.);
+        let _ = f.app.update(Message::Select(f.work));
+        let mut mounted = Mounted::new(&mut f.app).await;
+        f.app.zoom = 1.;
+        f.app.pan = Vector::ZERO;
+        f.app.fit_to_view = false;
+        mounted.settle(&mut f.app).await;
+        let canvas = canvas_bounds(&mut mounted, &f.app);
+        let slot = destination_bounds(&mut mounted, &f.app);
+        let from = at(&mut mounted, &f, xy(140., 245.));
+        let to = at(&mut mounted, &f, xy(160., 145.));
+        let before = f.app.document.bundle().clone();
+        mounted
+            .batch(
+                &mut f.app,
+                &[
+                    Input::Mouse(mouse::Event::CursorMoved { position: from }),
+                    Input::Mouse(mouse::Event::ButtonPressed(mouse::Button::Left)),
+                    Input::Mouse(mouse::Event::CursorMoved { position: to }),
+                ],
+                mouse::Cursor::Available(to),
+            )
+            .await;
+        assert_eq!(
+            f.app
+                .allocation_drag
+                .feedback
+                .as_ref()
+                .unwrap()
+                .destination_identity(),
+            name
+        );
+        assert!(f.app.allocation_drag.preview.is_some());
+        let hover = Point::new(slot.x + 45., slot.y + 8.);
+        mounted
+            .batch(
+                &mut f.app,
+                &[Input::Mouse(mouse::Event::CursorMoved { position: hover })],
+                mouse::Cursor::Available(hover),
+            )
+            .await;
+        let feedback = f.app.allocation_drag.feedback.as_ref().unwrap();
+        assert!(feedback.refused);
+        assert!(feedback.targets.is_empty());
+        assert_eq!(feedback.destination_identity(), "No eligible destination");
+        assert!(
+            feedback
+                .inspection_identity()
+                .contains(&format!("Last target: {name}"))
+        );
+        assert!(f.app.allocation_drag.preview.is_none());
+        assert!(f.app.allocation_drag.active.is_some());
+        assert!(f.app.status.starts_with("Pointer outside canvas"));
+        let inspected = mounted.pixels_at(&f.app, mouse::Cursor::Available(hover));
+        // Iced's Tooltip overlay draws its child but exposes no Operation
+        // traversal. Compare the real rendered overlay instead of inventing
+        // container geometry that the installed widget cannot report.
+        let inspection = std::mem::take(
+            &mut f
+                .app
+                .allocation_drag
+                .feedback
+                .as_mut()
+                .unwrap()
+                .inspection_targets,
+        );
+        let without_name = mounted.pixels_at(&f.app, mouse::Cursor::Available(hover));
+        let width = f.app.window_size.width as usize;
+        assert_ne!(
+            inspected, without_name,
+            "full captured name changes the actual hovered tooltip"
+        );
+        assert_eq!(
+            canvas_pixels(&inspected, width, canvas),
+            canvas_pixels(&without_name, width, canvas)
+        );
+        assert_eq!(
+            canvas_pixels(&inspected, width, slot),
+            canvas_pixels(&without_name, width, slot)
+        );
+        f.app
+            .allocation_drag
+            .feedback
+            .as_mut()
+            .unwrap()
+            .inspection_targets = inspection;
+        assert_eq!(canvas_bounds(&mut mounted, &f.app), canvas);
+        record_render_evidence(
+            &format!("{layer:?}-name-inspection"),
+            &inspected,
+            &f.app,
+            slot,
+            canvas,
+        );
+        assert_eq!(f.app.document.bundle(), &before);
+        assert!(!f.app.document.can_undo());
+
+        // Inspection grants no mutation authority. Releasing over it cancels.
+        mounted
+            .batch(
+                &mut f.app,
+                &[Input::Mouse(mouse::Event::ButtonReleased(
+                    mouse::Button::Left,
+                ))],
+                mouse::Cursor::Available(hover),
+            )
+            .await;
+        assert!(f.app.allocation_drag.active.is_none());
+        assert!(f.app.allocation_drag.feedback.is_none());
+        assert_eq!(f.app.status, "Work drag canceled outside the canvas.");
+        assert_eq!(f.app.document.bundle(), &before);
+        assert!(!f.app.document.can_undo());
+        // A fresh gesture cannot inherit the previous inspection name.
+        mounted
+            .batch(
+                &mut f.app,
+                &[
+                    Input::Mouse(mouse::Event::CursorMoved { position: from }),
+                    Input::Mouse(mouse::Event::ButtonPressed(mouse::Button::Left)),
+                    Input::Mouse(mouse::Event::CursorMoved { position: hover }),
+                ],
+                mouse::Cursor::Available(hover),
+            )
+            .await;
+        let feedback = f.app.allocation_drag.feedback.as_ref().unwrap();
+        assert!(feedback.inspection_targets.is_empty());
+        assert!(!feedback.inspection_identity().contains(name));
+        mounted
+            .batch(
+                &mut f.app,
+                &[
+                    Input::Mouse(mouse::Event::CursorMoved { position: to }),
+                    Input::Mouse(mouse::Event::ButtonReleased(mouse::Button::Left)),
+                ],
+                mouse::Cursor::Available(to),
+            )
+            .await;
+        assert_eq!(
+            validation::effective_performer(f.app.project(), f.work),
+            Some(f.a)
+        );
+        assert_eq!(f.app.document.revision(), 1);
+        let _ = f.app.update(Message::Undo);
+        assert_eq!(f.app.document.bundle(), &before);
+    }
+}

crates/oa-desktop/src/app/allocation_drag_tests/navigation_union.rs

@@ -0,0 +1,203 @@
+//! Captured real canvas packets against a later navigation or live gesture.
+use super::*;
+use crate::diagram_usage::{self as usage, Target};
+
+fn navigate_work(f: &mut Fixture) -> usage::Usage {
+    let message = f.app.diagram_usage_message(f.work);
+    let _ = f.app.update(message);
+    let panel = f.app.diagram_usages.as_ref().unwrap();
+    let token = panel.token;
+    let context = panel.context;
+    let process = f.app.behavior.topology.usage_snapshot().into_query_state();
+    let completion = usage::Completion {
+        token,
+        context,
+        result: Ok(usage::collect(
+            f.app.project(),
+            f.work,
+            &process,
+            &crate::behavior::scenario::State::default(),
+        )),
+    };
+    let _ = f.app.update(Message::DiagramUsagesReady(completion));
+    let found = f
+        .app
+        .diagram_usages
+        .as_ref()
+        .unwrap()
+        .usages
+        .iter()
+        .find(|usage| usage.target == Target::Placement(f.node))
+        .unwrap()
+        .clone();
+    let _ = f.app.update(Message::DiagramUsage(usage::Event::Choose(
+        token,
+        found.clone(),
+    )));
+    assert!(f.app.pending_diagram_reveal.is_some());
+    assert!(f.app.diagram_focus(found.surface).is_some());
+    found
+}
+
+fn assert_stale_noop(app: &mut App, message: Message) {
+    let before = app.document.snapshot();
+    let selection = (app.selected, app.selected_node, app.active_diagram);
+    let camera = (app.zoom, app.pan, app.canvas_epoch, app.camera_epoch);
+    let pending = app.pending_diagram_reveal.clone();
+    let focus = app
+        .diagram_navigation_focus
+        .as_ref()
+        .map(|focus| (focus.context, focus.usage.clone(), focus.selected));
+    let allocation = (app.allocation_drag.epoch, app.allocation_drag.arrange_next);
+    let active = app
+        .allocation_drag
+        .active
+        .as_ref()
+        .map(|active| (active.press.token, active.cache.len()));
+    let interaction = app.source_symbols.interaction;
+    let status = app.status.clone();
+    let _ = app.update(message);
+    assert_eq!(
+        (app.selected, app.selected_node, app.active_diagram),
+        selection
+    );
+    assert_eq!(
+        (app.zoom, app.pan, app.canvas_epoch, app.camera_epoch),
+        camera
+    );
+    assert_eq!(app.pending_diagram_reveal, pending);
+    assert_eq!(
+        app.diagram_navigation_focus.as_ref().map(|focus| (
+            focus.context,
+            focus.usage.clone(),
+            focus.selected
+        )),
+        focus
+    );
+    assert_eq!(
+        (app.allocation_drag.epoch, app.allocation_drag.arrange_next),
+        allocation
+    );
+    assert_eq!(
+        app.allocation_drag
+            .active
+            .as_ref()
+            .map(|active| (active.press.token, active.cache.len())),
+        active
+    );
+    assert_eq!(app.source_symbols.interaction, interaction);
+    assert_eq!(app.status, status);
+    assert!(Arc::ptr_eq(&before, &app.document.snapshot()));
+    assert_eq!(app.source_workspace.bundle(), before.bundle);
+}
+
+fn stale_packets(press: &Press) -> Vec<Message> {
+    vec![
+        Message::WorkDrag(Event::Cancel(press.token)),
+        Message::WorkDrag(Event::Preview(press.stamp, press.token, Some(press.start))),
+        Message::WorkDrag(Event::Release(press.stamp, press.token, Some(press.start))),
+        Message::WorkDrag(Event::Refused(press.stamp.epoch, "old refusal".into())),
+    ]
+}
+
+#[test]
+fn stale_gesture_packets_preserve_navigation_and_a_new_live_cancel_still_works() {
+    let mut f = fixture(Layer::Oa);
+    let before = f.app.document.snapshot();
+    let old = press(&f);
+    let _ = f.app.update(Message::WorkDrag(Event::Press(old.clone())));
+    assert_eq!(
+        f.app.allocation_drag.active.as_ref().unwrap().press.token,
+        old.token
+    );
+    let found = navigate_work(&mut f);
+    assert!(f.app.allocation_drag.active.is_none());
+    assert_ne!(f.app.allocation_drag.epoch, old.stamp.epoch);
+    for message in stale_packets(&old) {
+        assert_stale_noop(&mut f.app, message);
+    }
+    // A rejected press still explains the invalid view, but cannot consume the
+    // new destination's pending first measurement.
+    let pending = f.app.pending_diagram_reveal.clone();
+    let epoch = f.app.allocation_drag.epoch;
+    let _ = f.app.update(Message::WorkDrag(Event::Press(old.clone())));
+    assert_eq!(f.app.pending_diagram_reveal, pending);
+    assert_eq!(f.app.allocation_drag.epoch, epoch);
+    assert!(f.app.diagram_focus(found.surface).is_some());
+    assert_eq!(f.app.status, "The view changed. Start this drag again.");
+    let (context, _, epoch) = f.app.pending_diagram_reveal.clone().unwrap();
+    let _ = f.app.update(Message::DiagramRevealViewport(
+        context,
+        epoch,
+        bounds().size(),
+    ));
+    assert!(f.app.pending_diagram_reveal.is_none());
+    assert!(f.app.diagram_focus(found.surface).is_some());
+
+    // Restore the fixture's camera through current App actions, then capture a
+    // fresh packet through the actual DiagramCanvas rather than seeding active.
+    let factor = 1. / f.app.zoom;
+    let _ = f.app.update(Message::Zoom(factor));
+    let delta = -f.app.pan;
+    let _ = f.app.update(Message::Pan(delta));
+    let current = press(&f);
+    let _ = f
+        .app
+        .update(Message::WorkDrag(Event::Press(current.clone())));
+    assert_eq!(
+        f.app.allocation_drag.active.as_ref().unwrap().press.token,
+        current.token
+    );
+    assert!(
+        f.app.diagram_navigation_focus.is_none(),
+        "live press retires navigation"
+    );
+    for message in stale_packets(&old) {
+        assert_stale_noop(&mut f.app, message);
+    }
+    let epoch = f.app.allocation_drag.epoch;
+    let _ = f
+        .app
+        .update(Message::WorkDrag(Event::Cancel(current.token)));
+    assert!(f.app.allocation_drag.active.is_none());
+    assert!(f.app.allocation_drag.epoch > epoch);
+    assert_eq!(f.app.status, "Work drag canceled");
+    assert!(Arc::ptr_eq(&before, &f.app.document.snapshot()));
+    assert_eq!(f.app.source_workspace.bundle(), before.bundle);
+}
+
+#[test]
+fn old_chooser_envelopes_preserve_a_current_canvas_gesture() {
+    let mut previous = fixture(Layer::Oa);
+    let old_open = previous.app.diagram_usage_message(previous.work);
+    let _ = previous.app.update(old_open.clone());
+    let old_token = previous.app.diagram_usages.as_ref().unwrap().token;
+    let mut f = fixture(Layer::Oa);
+    let current = press(&f);
+    let _ = f
+        .app
+        .update(Message::WorkDrag(Event::Press(current.clone())));
+    assert_stale_noop(&mut f.app, old_open);
+    assert_stale_noop(
+        &mut f.app,
+        Message::DiagramUsage(usage::Event::Close(old_token)),
+    );
+    assert_stale_noop(
+        &mut f.app,
+        Message::DiagramUsage(usage::Event::Search(old_token, "old".into())),
+    );
+    assert_eq!(
+        f.app.allocation_drag.active.as_ref().unwrap().press.token,
+        current.token
+    );
+    let open = f.app.diagram_usage_message(f.work);
+    let _ = f.app.update(open);
+    assert!(
+        f.app.diagram_usages.is_some(),
+        "current chooser remains live"
+    );
+    assert!(
+        f.app.allocation_drag.active.is_none(),
+        "current chooser retires gesture"
+    );
+}

crates/oa-desktop/src/app/architecture_authoring.rs

@@ -138,7 +138,7 @@ pub fn validate_saved(p: &Project, s: &Saved) -> Result<(), String> {
         .diagrams
         .get(&s.diagram)
         .ok_or("The creation draft's diagram is missing.")?;
-    if matches!(d.projection, ProjectionKind::StateMachine { .. })
+    if !d.projection.is_architecture()
         || s.query.len() > 16384
         || s.page > 1_000_000
         || s.point
@@ -180,7 +180,7 @@ pub fn validate_saved(p: &Project, s: &Saved) -> Result<(), String> {
 }
 fn context_kinds(p: &Project, d: &Diagram) -> Vec<Kind> {
     let mut values = match (d.layer, d.projection) {
-        (_, ProjectionKind::StateMachine { .. }) => vec![],
+        (_, ProjectionKind::StateMachine { .. } | ProjectionKind::Scenario { .. }) => vec![],
         (Layer::Oa, ProjectionKind::FunctionalDataflow) => vec![Kind::Activity],
         (Layer::Sa, ProjectionKind::FunctionalDataflow) => vec![Kind::Function],
         (Layer::Oa, ProjectionKind::Capabilities) => vec![
@@ -208,11 +208,12 @@ pub fn kinds(app: &App) -> Vec<Kind> {
         .unwrap_or_default()
 }
 fn compatible(p: &Project, d: &Diagram, id: Id) -> bool {
-    p.elements.get(&id).is_some_and(|e| {
-        e.kind() != Kind::Port
-            && d.projection.includes(e.kind())
-            && (e.layer() == d.layer || d.projection == ProjectionKind::Traceability)
-    })
+    d.projection.is_architecture()
+        && p.elements.get(&id).is_some_and(|e| {
+            e.kind() != Kind::Port
+                && d.projection.includes(e.kind())
+                && (e.layer() == d.layer || d.projection == ProjectionKind::Traceability)
+        })
 }
 fn suggested(p: &Project, d: &Diagram, kind: Kind) -> bool {
     // Existing System remains a useful choice even when the singleton exists.
@@ -257,6 +258,17 @@ pub fn candidates(app: &App) -> Vec<(Id, String, bool)> {
 }
 impl App {
     pub(super) fn architecture_event(&mut self, event: Event) -> Task<Message> {
+        if matches!(
+            &event,
+            Event::Start(..) | Event::Allocate(..) | Event::Existing(..)
+        ) && !self
+            .active_diagram
+            .and_then(|id| self.project().diagrams.get(&id))
+            .is_some_and(|d| d.projection.is_architecture())
+        {
+            self.status = "Choose an architecture view before adding architecture content.".into();
+            return Task::none();
+        }
         match event {
             Event::Start(_, point) | Event::Allocate(_, _, point) | Event::Existing(point) => {
                 if self.architecture.is_some() {

crates/oa-desktop/src/app/architecture_authoring/tests.rs

@@ -70,13 +70,16 @@ fn architecture_f2_routes_selected_node_to_inline_rename_and_exact_undo() {
         view_index: None,
         diagram: app.active_diagram.unwrap(),
         selected: element,
+        navigation_focus: None,
         zoom: app.zoom,
         pan: app.pan,
         context: app.route_context().unwrap(),
         selected_bend: None,
+        selected_attachment: None,
         editable: true,
         placing: false,
         connection: None,
+        allocation: None,
     };
     let mut state = crate::diagram::State::default();
     let key = CanvasEvent::Keyboard(keyboard::Event::KeyPressed {
@@ -88,17 +91,8 @@ fn architecture_f2_routes_selected_node_to_inline_rename_and_exact_undo() {
         text: None,
         repeat: false,
     });
-    assert!(
-        canvas
-            .update(&mut state, &key, bounds, mouse::Cursor::Unavailable)
-            .is_none()
-    );
-    let _ = canvas.update(
-        &mut state,
-        &CanvasEvent::Mouse(mouse::Event::ButtonPressed(mouse::Button::Left)),
-        bounds,
-        mouse::Cursor::Available(iced::Point::new(150., 120.)),
-    );
+    // Program receives keys already admitted by diagram::focus::Owner. Real
+    // unfocused/Inspector refusal is covered by app::diagram_focus_tests.
     let action = canvas
         .update(&mut state, &key, bounds, mouse::Cursor::Unavailable)
         .unwrap();

crates/oa-desktop/src/app/architecture_authoring_tests.rs

@@ -225,13 +225,16 @@ fn architecture_canvas_left_click_uses_world_coordinate_once_at_zoom_and_pan() {
         view_index: None,
         diagram: app.active_diagram.unwrap(),
         selected: app.selected,
+        navigation_focus: None,
         zoom: app.zoom,
         pan: app.pan,
         context: app.route_context().unwrap(),
         selected_bend: None,
+        selected_attachment: None,
         editable: true,
         placing: true,
         connection: None,
+        allocation: None,
     };
     let mut state = crate::diagram::State::default();
     let action = canvas
@@ -279,6 +282,164 @@ fn architecture_cancelled_gesture_cannot_commit_a_later_named_draft() {
     assert!(app.architecture.is_some());
 }
 
+#[test]
+fn architecture_f2_rename_preserves_identity_placement_and_atomic_history() {
+    use iced::{keyboard, mouse, widget::canvas::Program};
+    let mut app = setup(Layer::Oa);
+    send(
+        &mut app,
+        Event::Start(Kind::Entity, Some(Position { x: 200., y: 120. })),
+    );
+    send(&mut app, Event::Name("Response team".into()));
+    send(&mut app, Event::Submit);
+    let before = app.document.bundle().clone();
+    let element = app.selected;
+    let node = app.selected_node;
+    let diagrams = app.project().diagrams.clone();
+    let camera = (app.zoom, app.pan);
+    let canvas = crate::diagram::DiagramCanvas {
+        project: app.project(),
+        view_index: None,
+        diagram: app.active_diagram.unwrap(),
+        selected: element,
+        navigation_focus: None,
+        zoom: app.zoom,
+        pan: app.pan,
+        context: app.route_context().unwrap(),
+        selected_bend: None,
+        selected_attachment: None,
+        editable: true,
+        placing: false,
+        connection: None,
+        allocation: None,
+    };
+    let bounds = iced::Rectangle::with_size(iced::Size::new(800., 600.));
+    let cursor = mouse::Cursor::Available(iced::Point::new(500., 400.));
+    let mut state = crate::diagram::State::default();
+    let key = iced::widget::canvas::Event::Keyboard(keyboard::Event::KeyPressed {
+        key: keyboard::Key::Named(keyboard::key::Named::F2),
+        modified_key: keyboard::Key::Named(keyboard::key::Named::F2),
+        physical_key: keyboard::key::Physical::Code(keyboard::key::Code::F2),
+        location: keyboard::Location::Standard,
+        modifiers: keyboard::Modifiers::empty(),
+        text: None,
+        repeat: false,
+    });
+    // Program receives keys already admitted by diagram::focus::Owner. Real
+    // unfocused/Inspector refusal is covered by app::diagram_focus_tests.
+    let message = canvas
+        .update(&mut state, &key, bounds, cursor)
+        .expect("admitted F2 opens the selected semantic name")
+        .into_inner()
+        .0
+        .unwrap();
+    let _ = app.update(message);
+    assert!(app.architecture.as_ref().unwrap().inline());
+    send(&mut app, Event::Name("  Emergency team 雨  ".into()));
+    assert_eq!(app.document.bundle(), &before);
+    send(&mut app, Event::Submit);
+    assert!(app.architecture.is_none());
+    assert_eq!((app.selected, app.selected_node), (element, node));
+    assert_eq!(
+        app.project().elements[&element].name,
+        "  Emergency team 雨  "
+    );
+    assert_eq!(app.project().diagrams, diagrams);
+    assert_eq!((app.zoom, app.pan), camera);
+    let accepted = app.document.bundle().clone();
+    let _ = app.update(Message::Undo);
+    assert_eq!(app.document.bundle(), &before);
+    let _ = app.update(Message::Redo);
+    assert_eq!(app.document.bundle(), &accepted);
+    let context = app.route_context().unwrap();
+    send(
+        &mut app,
+        Event::Rename(context, element, Position { x: 200., y: 120. }),
+    );
+    send(&mut app, Event::Name("Cancelled name".into()));
+    let _ = app.update(Message::Escape);
+    assert!(app.architecture.is_none());
+    assert_eq!(app.document.bundle(), &accepted);
+}
+
+#[test]
+fn architecture_contextual_allocation_creates_work_relation_and_node_in_one_undo() {
+    for (layer, performer_kind, work_kind) in [
+        (Layer::Oa, Kind::Entity, Kind::Activity),
+        (Layer::Sa, Kind::System, Kind::Function),
+    ] {
+        let mut app = setup(layer);
+        send(
+            &mut app,
+            Event::Start(performer_kind, Some(Position { x: 20., y: 20. })),
+        );
+        send(&mut app, Event::Name("Control team".into()));
+        send(&mut app, Event::Submit);
+        let performer = app.selected;
+        let before = app.document.bundle().clone();
+        send(
+            &mut app,
+            Event::Allocate(work_kind, performer, Some(Position { x: 55., y: 90. })),
+        );
+        send(&mut app, Event::Name("Assess pressure".into()));
+        assert_eq!(app.document.bundle(), &before);
+        send(&mut app, Event::Submit);
+        assert!(app.architecture.is_none(), "{}", app.status);
+        let work = app.selected;
+        assert_eq!(app.project().elements[&work].parent, None);
+        assert!(
+            app.project()
+                .relations
+                .values()
+                .any(|r| r.kind() == RelationKind::Allocation
+                    && r.source() == performer
+                    && r.target() == work)
+        );
+        let node = &app.project().diagrams[&app.active_diagram.unwrap()].nodes
+            [&app.selected_node.unwrap()];
+        assert_eq!(node.position, Position { x: 55., y: 90. });
+        let accepted = app.document.bundle().clone();
+        let _ = app.update(Message::Undo);
+        assert_eq!(app.document.bundle(), &before);
+        let _ = app.update(Message::Redo);
+        assert_eq!(app.document.bundle(), &accepted);
+    }
+}
+
+#[test]
+fn architecture_rejected_submission_keeps_inline_name_visible_and_invalid_click_is_ignored() {
+    let mut app = setup(Layer::Oa);
+    send(&mut app, Event::Start(Kind::Entity, None));
+    let context = app.route_context().unwrap();
+    send(
+        &mut app,
+        Event::Click(
+            context,
+            Position {
+                x: f32::NAN,
+                y: 30.,
+            },
+        ),
+    );
+    assert!(app.architecture.as_ref().unwrap().unnamed_tool());
+    send(&mut app, Event::Click(context, Position { x: 40., y: 30. }));
+    send(&mut app, Event::Name("Retained team".into()));
+    // A replaced document must not accept a queued draft submission.
+    app.canvas_document = Id::new_v4();
+    let before = app.document.bundle().clone();
+    send(&mut app, Event::Submit);
+    let draft = app.architecture.as_ref().unwrap();
+    assert!(draft.inline());
+    assert!(draft.error.is_some());
+    assert!(
+        matches!(&draft.saved.intent, architecture_authoring::Intent::Create { name, .. } if name == "Retained team")
+    );
+    assert_eq!(app.document.bundle(), &before);
+    let _ = app.update(Message::Escape);
+    assert!(app.architecture.is_none());
+    assert_eq!(app.document.bundle(), &before);
+}
+
 #[test]
 fn basic_transition_explicit_overview_focus_wins_over_an_already_populated_architecture() {
     use crate::workflow::{Event as W, Workflow};

crates/oa-desktop/src/app/behavior_lifecycle_tests.rs

@@ -291,7 +291,7 @@ fn pending_behavior_blocks_navigation_property_edits_and_model_history() {
         Message::BrowseGroup(crate::explorer::Group::Work),
         Message::Field("/name".into(), "Overwrite properties".into()),
         Message::Command(Command::Rename(fixture.source, "Overwrite model".into())),
-        Message::ConfirmDelete,
+        Message::ConfirmDelete(0),
         Message::Undo,
         Message::Redo,
         Message::ShortcutUndo(false),

crates/oa-desktop/src/app/behavior_removal_tests.rs

@@ -0,0 +1,620 @@
+//! Delete through the actual App widget tree, ordinary focus, and source history.
+use super::*;
+use crate::behavior::{
+    canvas_workspace::tests::{Mounted, focused, key},
+    scenario, topology,
+};
+use iced::{Event as Input, Point, Size, Vector, keyboard, mouse};
+
+fn app(p: Project, owner: Id) -> App {
+    let mut app = App::with_project(p);
+    let _ = app.update(Message::Select(owner));
+    let _ = app.update(Message::Page(Page::Behavior));
+    app.window_size = Size::new(1900., 1200.);
+    app
+}
+fn point(mounted: &mut Mounted, app: &App, id: Id) -> Point {
+    if let Some(context) = app.topology_context() {
+        let bounds = mounted.geometry(app).bounds("process-viewport");
+        let local = app
+            .behavior
+            .topology
+            .removal_test_point(app, context.owner, id, None);
+        bounds.position() + Vector::new(local.x, local.y)
+    } else {
+        let context = app.scenario_context().unwrap();
+        let bounds = mounted.geometry(app).bounds("scenario-viewport");
+        let local = scenario::removal_test_point(app, context.scenario, id);
+        bounds.position() + Vector::new(local.x, local.y)
+    }
+}
+async fn select(mounted: &mut Mounted, app: &mut App, id: Id) {
+    let target = point(mounted, app, id);
+    mounted.click(app, target).await;
+    assert_eq!(app.selected, id, "real pointer selects intended occurrence");
+}
+fn remove_key(shift: bool) -> Input {
+    let mut event = key(keyboard::key::Named::Delete);
+    if shift && let Input::Keyboard(keyboard::Event::KeyPressed { modifiers, .. }) = &mut event {
+        *modifiers = keyboard::Modifiers::SHIFT;
+    }
+    event
+}
+fn removal(message: &Message) -> bool {
+    matches!(
+        message,
+        Message::TopologyCanvas(topology::CanvasEvent::Remove(..))
+            | Message::ScenarioCanvas(scenario::CanvasEvent::Remove(..))
+    )
+}
+async fn delete(mounted: &mut Mounted, app: &mut App, shift: bool) -> u64 {
+    let messages = mounted
+        .batch(app, &[remove_key(shift)], mouse::Cursor::Unavailable)
+        .await;
+    assert!(
+        messages.iter().any(removal),
+        "focused viewport emits removal: {messages:?}"
+    );
+    let target = app.delete_target.as_ref().expect("captured confirmation");
+    assert_eq!(target.snapshot.request.object, app.selected);
+    assert_eq!(target.placement, None);
+    assert_eq!(target.snapshot.request.placement, None);
+    target.snapshot.token
+}
+async fn send(mounted: &mut Mounted, app: &mut App, message: Message) {
+    let task = app.update(message);
+    mounted.perform(app, task).await;
+}
+fn consistent(app: &App) {
+    assert_eq!(
+        source_project::compile_bundle(app.document.bundle(), LIMITS)
+            .unwrap()
+            .decoded
+            .project,
+        *app.project()
+    );
+    assert_eq!(
+        source_workspace::reachable(&app.source_workspace.bundle()).unwrap(),
+        *app.document.bundle()
+    );
+}
+
+#[tokio::test]
+async fn mounted_process_delete_occurrence_or_link_preserves_reusable_work_and_source_history() {
+    for layer in [Layer::Oa, Layer::Sa] {
+        for link in [false, true] {
+            let f = topology::direct_tests::fixture(layer);
+            let target = if link { f.link } else { f.nodes[0] };
+            let mut app = app(f.p.clone(), f.owner);
+            let mut mounted = Mounted::new(&mut app).await;
+            let original = app.document.bundle().clone();
+            select(&mut mounted, &mut app, target).await;
+            // No extra redraw between release and first Delete.
+            let token = delete(&mut mounted, &mut app, link).await;
+            assert_eq!(
+                app.delete_target.as_ref().unwrap().behavior_owner,
+                Some(f.owner)
+            );
+            assert_eq!(app.document.bundle(), &original);
+            send(&mut mounted, &mut app, Message::ConfirmDelete(token)).await;
+            assert!(!app.project().contains(target));
+            assert!(f.work.iter().all(|id| app.project().contains(*id)));
+            assert!(app.project().contains(f.exchange));
+            assert!(app.project().contains(f.nodes[1]));
+            assert_eq!(app.project().contains(f.nodes[0]), link);
+            assert!(!app.project().contains(f.link));
+            consistent(&app);
+            let removed = app.document.bundle().clone();
+            send(&mut mounted, &mut app, Message::Undo).await;
+            assert_eq!(app.document.bundle(), &original);
+            consistent(&app);
+            send(&mut mounted, &mut app, Message::Redo).await;
+            assert_eq!(app.document.bundle(), &removed);
+            consistent(&app);
+        }
+    }
+}
+
+#[tokio::test]
+async fn mounted_scenario_delete_message_or_participant_preserves_reusable_targets() {
+    for participant in [false, true] {
+        let f = scenario::direct_tests::fixture();
+        let target = if participant { f.sender } else { f.call };
+        let mut app = app(f.project.clone(), f.owner);
+        let mut mounted = Mounted::new(&mut app).await;
+        let original = app.document.bundle().clone();
+        select(&mut mounted, &mut app, target).await;
+        let token = delete(&mut mounted, &mut app, participant).await;
+        send(&mut mounted, &mut app, Message::ConfirmDelete(token)).await;
+        assert!(!app.project().contains(target));
+        assert!(app.project().contains(f.exchange));
+        assert!(app.project().contains(f.receiver));
+        assert!(app.project().contains(f.reply));
+        for element in f
+            .project
+            .elements
+            .values()
+            .filter(|element| element.parent != Some(f.owner))
+        {
+            assert!(
+                app.project().contains(element.id),
+                "referenced definitions survive"
+            );
+        }
+        if participant {
+            assert!(app.project().contains(f.call));
+            for element in app.project().elements.values() {
+                if let Some(SharedBody::Occurrence {
+                    body:
+                        OccurrenceBody::Exchange {
+                            sender, receiver, ..
+                        },
+                    ..
+                }) = element.shared()
+                {
+                    assert_ne!(*sender, Some(target));
+                    assert_ne!(*receiver, Some(target));
+                }
+            }
+        }
+        consistent(&app);
+        send(&mut mounted, &mut app, Message::Undo).await;
+        assert_eq!(app.document.bundle(), &original);
+        consistent(&app);
+    }
+}
+
+#[tokio::test]
+async fn mounted_scenario_use_delete_keeps_definition_and_second_use_and_rejects_owner_replay() {
+    let (p, owners, uses) = scenario::direct_tests::navigation_fixture();
+    let mut app = app(p, owners[0]);
+    let mut mounted = Mounted::new(&mut app).await;
+    let original = app.document.bundle().clone();
+    select(&mut mounted, &mut app, uses[0]).await;
+    let stale = delete(&mut mounted, &mut app, false).await;
+    send(&mut mounted, &mut app, Message::CancelDelete).await;
+    send(&mut mounted, &mut app, Message::ConfirmDelete(stale)).await;
+    assert_eq!(app.document.bundle(), &original);
+    select(&mut mounted, &mut app, uses[0]).await;
+    let token = delete(&mut mounted, &mut app, true).await;
+    send(&mut mounted, &mut app, Message::ConfirmDelete(stale)).await;
+    assert!(app.delete_pending, "old token does not cancel new dialog");
+    // Keep selection and epoch deliberately unchanged: owner is an independent witness.
+    let captured = app.scenario_context().unwrap();
+    assert_eq!(captured.scenario, owners[0]);
+    assert_eq!(
+        app.delete_target.as_ref().unwrap().behavior_owner,
+        Some(owners[0])
+    );
+    app.behavior.active_owner = Some(owners[1]);
+    app.reconcile_scenario_workspace();
+    let other = app.scenario_context().unwrap();
+    assert_eq!(other.scenario, owners[1]);
+    assert_eq!(
+        other.representation,
+        crate::behavior::scenario_layout::Representation::Derived { owner: owners[1] }
+    );
+    assert_eq!(other.epoch, captured.epoch);
+    assert_eq!(app.selected, uses[0]);
+    assert!(
+        app.delete_target.as_ref().unwrap().snapshot.valid(&app),
+        "the independent owner guard must reject an otherwise current token"
+    );
+    send(&mut mounted, &mut app, Message::ConfirmDelete(token)).await;
+    assert_eq!(app.document.bundle(), &original);
+    assert!(!app.delete_pending && app.delete_target.is_none());
+    assert!(!app.document.can_undo() && !app.document.can_redo());
+    app.behavior.active_owner = Some(owners[0]);
+    // Restore both owner and qualified presentation before mounting pointer input.
+    // Passive reports from the previous owner cannot repair an inconsistent fixture.
+    app.reconcile_scenario_workspace();
+    assert_eq!(app.scenario_context().unwrap().scenario, owners[0]);
+    assert_eq!(app.selected, uses[0]);
+    mounted.settle(&mut app).await;
+    select(&mut mounted, &mut app, uses[0]).await;
+    let token = delete(&mut mounted, &mut app, false).await;
+    send(&mut mounted, &mut app, Message::ConfirmDelete(token)).await;
+    assert!(!app.project().contains(uses[0]));
+    assert!(app.project().contains(uses[1]));
+    assert!(owners.iter().all(|id| app.project().contains(*id)));
+    consistent(&app);
+    send(&mut mounted, &mut app, Message::Undo).await;
+    assert_eq!(app.document.bundle(), &original);
+}
+
+#[tokio::test]
+async fn mounted_behavior_tab_and_f6_retire_same_batch_delete_and_window_focus() {
+    for process in [false, true] {
+        let (mut app, target) = if process {
+            let f = topology::direct_tests::fixture(Layer::Oa);
+            (app(f.p, f.owner), f.nodes[0])
+        } else {
+            let f = scenario::direct_tests::fixture();
+            (app(f.project, f.owner), f.call)
+        };
+        let mut mounted = Mounted::new(&mut app).await;
+        let original = app.document.bundle().clone();
+        for boundary in [
+            keyboard::key::Named::Tab,
+            keyboard::key::Named::F6,
+            keyboard::key::Named::Escape,
+        ] {
+            select(&mut mounted, &mut app, target).await;
+            let messages = mounted
+                .batch(
+                    &mut app,
+                    &[key(boundary), remove_key(false)],
+                    mouse::Cursor::Unavailable,
+                )
+                .await;
+            assert!(
+                !messages.iter().any(removal),
+                "{boundary:?} retires keyboard admission within the batch"
+            );
+            assert!(!app.delete_pending);
+            assert_eq!(app.document.bundle(), &original);
+            assert!(!focused(&mut mounted, &app, "viewport"));
+            if boundary == keyboard::key::Named::Tab {
+                assert_eq!(
+                    mounted
+                        .geometry(&app)
+                        .focused
+                        .iter()
+                        .filter(|(_, _, value)| *value)
+                        .count(),
+                    1,
+                    "Tab completes traversal to one real control"
+                );
+                let mut backwards = key(keyboard::key::Named::Tab);
+                if let Input::Keyboard(keyboard::Event::KeyPressed { modifiers, .. }) =
+                    &mut backwards
+                {
+                    *modifiers = keyboard::Modifiers::SHIFT;
+                }
+                mounted
+                    .batch(&mut app, &[backwards], mouse::Cursor::Unavailable)
+                    .await;
+            } else {
+                let messages = mounted
+                    .batch(
+                        &mut app,
+                        &[key(keyboard::key::Named::F6), remove_key(false)],
+                        mouse::Cursor::Unavailable,
+                    )
+                    .await;
+                assert!(
+                    !messages.iter().any(removal),
+                    "F6 entry completes after the batch, before a later Delete"
+                );
+            }
+            assert!(
+                focused(&mut mounted, &app, "viewport"),
+                "{boundary:?} supports keyboard-only return to the viewport"
+            );
+            delete(&mut mounted, &mut app, false).await;
+            send(&mut mounted, &mut app, Message::CancelDelete).await;
+            assert_eq!(app.document.bundle(), &original);
+        }
+        select(&mut mounted, &mut app, target).await;
+        let messages = mounted
+            .batch(
+                &mut app,
+                &[
+                    Input::Window(iced::window::Event::Unfocused),
+                    remove_key(false),
+                ],
+                mouse::Cursor::Unavailable,
+            )
+            .await;
+        assert!(!messages.iter().any(removal));
+        assert!(!app.delete_pending);
+        // A new actual click reacquires ownership after each boundary.
+        select(&mut mounted, &mut app, target).await;
+        delete(&mut mounted, &mut app, false).await;
+        send(&mut mounted, &mut app, Message::CancelDelete).await;
+        assert_eq!(app.document.bundle(), &original);
+    }
+}
+
+#[tokio::test]
+async fn mounted_behavior_clean_inspector_click_and_tab_own_delete_then_f6_returns_to_canvas() {
+    for process in [false, true] {
+        for tab_entry in [false, true] {
+            let (mut app, target) = if process {
+                let f = topology::direct_tests::fixture(Layer::Oa);
+                (app(f.p, f.owner), f.nodes[0])
+            } else {
+                let f = scenario::direct_tests::fixture();
+                (app(f.project, f.owner), f.call)
+            };
+            let mut mounted = Mounted::new(&mut app).await;
+            select(&mut mounted, &mut app, target).await;
+            let original = app.document.bundle().clone();
+            let original_name = app.draft.as_ref().unwrap().inputs["/name"].raw.clone();
+            // The first text input in the right-hand Inspector is the name.
+            // Verify its actual binding below, rather than seeding focus state.
+            let field = mounted
+                .geometry(&app)
+                .text_inputs
+                .into_iter()
+                .filter(|bounds| bounds.x > app.window_size.width - 320.)
+                .min_by(|a, b| a.y.total_cmp(&b.y))
+                .expect("visible Inspector name input");
+            if tab_entry {
+                // Canvas Tab stays within canvas controls. Escape then ordinary
+                // Tab follows the existing Inspector entry policy.
+                mounted
+                    .batch(
+                        &mut app,
+                        &[key(keyboard::key::Named::Escape)],
+                        mouse::Cursor::Unavailable,
+                    )
+                    .await;
+                mounted
+                    .batch(
+                        &mut app,
+                        &[key(keyboard::key::Named::Tab)],
+                        mouse::Cursor::Unavailable,
+                    )
+                    .await;
+            } else {
+                mounted.click(&mut app, field.center()).await;
+            }
+            assert!(
+                mounted
+                    .geometry(&app)
+                    .focused
+                    .iter()
+                    .any(|(_, bounds, value)| *bounds == field && *value),
+                "actual {} focuses the Inspector name",
+                if tab_entry { "Tab" } else { "click" }
+            );
+            assert!(!focused(&mut mounted, &app, "viewport"));
+            assert!(!app.draft_dirty());
+            let messages = mounted
+                .batch(
+                    &mut app,
+                    &[key(keyboard::key::Named::End), remove_key(true)],
+                    mouse::Cursor::Unavailable,
+                )
+                .await;
+            assert!(messages.iter().any(|message| matches!(
+                message,
+                Message::Field(path, value) if path == "/name" && *value == original_name
+            )));
+            assert!(!messages.iter().any(removal));
+            assert!(!app.delete_pending);
+            assert!(!app.draft_dirty(), "Delete at end keeps the field clean");
+            assert_eq!(app.document.bundle(), &original);
+            mounted
+                .batch(
+                    &mut app,
+                    &[key(keyboard::key::Named::F6)],
+                    mouse::Cursor::Unavailable,
+                )
+                .await;
+            assert!(focused(&mut mounted, &app, "viewport"));
+            assert_eq!(
+                mounted
+                    .geometry(&app)
+                    .focused
+                    .iter()
+                    .filter(|(_, _, value)| *value)
+                    .count(),
+                1,
+                "F6 releases actual Inspector focus"
+            );
+            delete(&mut mounted, &mut app, false).await;
+            send(&mut mounted, &mut app, Message::CancelDelete).await;
+            assert_eq!(app.document.bundle(), &original);
+        }
+    }
+}
+
+#[tokio::test]
+async fn mounted_behavior_clean_text_focus_and_modifiers_cannot_delete_selected_occurrence() {
+    use iced::advanced::widget::{Operation, operation};
+    struct FocusText(iced::Rectangle);
+    impl Operation for FocusText {
+        fn traverse(&mut self, visit: &mut dyn FnMut(&mut dyn Operation)) {
+            visit(self);
+        }
+        fn focusable(
+            &mut self,
+            _: Option<&iced::advanced::widget::Id>,
+            bounds: iced::Rectangle,
+            state: &mut dyn operation::Focusable,
+        ) {
+            if bounds == self.0 {
+                state.focus();
+            } else {
+                state.unfocus();
+            }
+        }
+    }
+    for process in [false, true] {
+        let (mut app, target) = if process {
+            let f = topology::direct_tests::fixture(Layer::Oa);
+            (app(f.p, f.owner), f.nodes[0])
+        } else {
+            let f = scenario::direct_tests::fixture();
+            (app(f.project, f.owner), f.call)
+        };
+        let mut mounted = Mounted::new(&mut app).await;
+        select(&mut mounted, &mut app, target).await;
+        let original = app.document.bundle().clone();
+        for modifiers in [
+            keyboard::Modifiers::CTRL,
+            keyboard::Modifiers::ALT,
+            keyboard::Modifiers::LOGO,
+        ] {
+            let mut event = remove_key(false);
+            if let Input::Keyboard(keyboard::Event::KeyPressed {
+                modifiers: value, ..
+            }) = &mut event
+            {
+                *value = modifiers;
+            }
+            let messages = mounted
+                .batch(&mut app, &[event], mouse::Cursor::Unavailable)
+                .await;
+            assert!(!messages.iter().any(removal));
+        }
+        let field = mounted
+            .geometry(&app)
+            .text_inputs
+            .into_iter()
+            .find(|bounds| bounds.width > 40.)
+            .expect("real text field");
+        mounted.operate(&app, &mut FocusText(field));
+        assert!(!app.draft_dirty());
+        let messages = mounted
+            .batch(&mut app, &[remove_key(true)], mouse::Cursor::Unavailable)
+            .await;
+        assert!(!messages.iter().any(removal));
+        assert!(!app.delete_pending);
+        assert_eq!(app.document.bundle(), &original);
+    }
+}
+
+#[tokio::test]
+async fn mounted_scenario_fragment_and_branch_delete_only_owned_occurrences() {
+    for whole_fragment in [false, true] {
+        let (f, branch, anchor, state, reused, remote) =
+            scenario::direct_tests::placement_fixture();
+        let fragment = f.project.elements[&branch].parent.unwrap();
+        let target = if whole_fragment { fragment } else { branch };
+        let mut app = app(f.project.clone(), f.owner);
+        let mut mounted = Mounted::new(&mut app).await;
+        let original = app.document.bundle().clone();
+        select(&mut mounted, &mut app, target).await;
+        let token = delete(&mut mounted, &mut app, false).await;
+        send(&mut mounted, &mut app, Message::ConfirmDelete(token)).await;
+        assert!(!app.project().contains(target));
+        assert!(!app.project().contains(anchor));
+        assert!(!app.project().contains(branch));
+        assert_eq!(app.project().contains(fragment), !whole_fragment);
+        for id in [
+            f.call, f.reply, f.sender, f.receiver, f.exchange, state, reused, remote,
+        ] {
+            assert!(app.project().contains(id));
+        }
+        consistent(&app);
+        send(&mut mounted, &mut app, Message::Undo).await;
+        assert_eq!(app.document.bundle(), &original);
+    }
+}
+
+#[tokio::test]
+async fn mounted_qualified_process_child_delete_refuses_outer_reference_and_shared_definition() {
+    let f = topology::direct_tests::fixture(Layer::Oa);
+    let mut p = f.p;
+    let caller = p
+        .add_element(Kind::Process, Layer::Oa, "Caller", None)
+        .unwrap();
+    let references = ["First use", "Second use"].map(|name| {
+        let mut element = p
+            .make_element(Kind::Occurrence, Layer::Oa, name, Some(caller))
+            .unwrap();
+        *element.shared_mut().unwrap() = SharedBody::Occurrence {
+            body: OccurrenceBody::SequenceReference {
+                sequence: Some(f.owner),
+            },
+            precondition: String::new(),
+            postcondition: String::new(),
+        };
+        let id = element.id;
+        p = execute_batch(&p, &[Command::CreateElement(element)]).unwrap();
+        id
+    });
+    let mut app = app(p, caller);
+    let mut mounted = Mounted::new(&mut app).await;
+    let original = app.document.bundle().clone();
+    let endpoint = OccurrenceEndpoint {
+        references: vec![references[0]],
+        occurrence: f.nodes[0],
+    };
+    let bounds = mounted.geometry(&app).bounds("process-viewport");
+    let local =
+        app.behavior
+            .topology
+            .removal_test_point(&app, caller, references[0], Some(&endpoint));
+    let messages = mounted
+        .click(&mut app, bounds.position() + Vector::new(local.x, local.y))
+        .await;
+    assert!(messages.iter().any(|message| matches!(
+        message,
+        Message::TopologyCanvas(topology::CanvasEvent::SelectQualified(..))
+    )));
+    assert_eq!(app.selected, references[0]);
+    assert!(
+        app.behavior
+            .topology
+            .has_qualified_selection(app.project(), caller)
+    );
+    mounted
+        .batch(&mut app, &[remove_key(false)], mouse::Cursor::Unavailable)
+        .await;
+    assert!(!app.delete_pending);
+    assert_eq!(app.document.bundle(), &original);
+    assert!(app.status.contains("Open the referenced definition"));
+    select(&mut mounted, &mut app, references[0]).await;
+    assert!(
+        !app.behavior
+            .topology
+            .has_qualified_selection(app.project(), caller)
+    );
+    let token = delete(&mut mounted, &mut app, true).await;
+    send(&mut mounted, &mut app, Message::ConfirmDelete(token)).await;
+    assert!(!app.project().contains(references[0]));
+    assert!(app.project().contains(references[1]));
+    assert!(app.project().contains(f.owner));
+    assert!(f.nodes.iter().all(|id| app.project().contains(*id)));
+    consistent(&app);
+    send(&mut mounted, &mut app, Message::Undo).await;
+    assert_eq!(app.document.bundle(), &original);
+}
+
+#[tokio::test]
+async fn mounted_behavior_pan_and_stale_removal_intent_do_not_delete() {
+    for process in [false, true] {
+        let (mut app, target) = if process {
+            let f = topology::direct_tests::fixture(Layer::Oa);
+            (app(f.p, f.owner), f.nodes[0])
+        } else {
+            let f = scenario::direct_tests::fixture();
+            (app(f.project, f.owner), f.call)
+        };
+        let mut mounted = Mounted::new(&mut app).await;
+        select(&mut mounted, &mut app, target).await;
+        let original = app.document.bundle().clone();
+        let cursor = point(&mut mounted, &app, target);
+        let messages = mounted
+            .batch(
+                &mut app,
+                &[
+                    Input::Mouse(mouse::Event::CursorMoved { position: cursor }),
+                    Input::Mouse(mouse::Event::ButtonPressed(mouse::Button::Middle)),
+                    remove_key(false),
+                    Input::Mouse(mouse::Event::ButtonReleased(mouse::Button::Middle)),
+                ],
+                mouse::Cursor::Available(cursor),
+            )
+            .await;
+        assert!(
+            !messages.iter().any(removal),
+            "held pan never becomes an occurrence deletion"
+        );
+        assert!(!app.delete_pending);
+        select(&mut mounted, &mut app, target).await;
+        let messages = mounted.input(&app, &[remove_key(false)], mouse::Cursor::Unavailable);
+        let stale = messages
+            .into_iter()
+            .find(removal)
+            .expect("captured live removal");
+        app.canvas_epoch = app.canvas_epoch.wrapping_add(1);
+        send(&mut mounted, &mut app, stale).await;
+        assert!(!app.delete_pending);
+        assert_eq!(app.document.bundle(), &original);
+    }
+}

crates/oa-desktop/src/app/checkpoints.rs

@@ -173,7 +173,12 @@ impl App {
         self.behavior = restored.behavior;
         self.workflow = restored.workflow;
         let focus = self.behavior.pending_owner().unwrap_or(self.selected);
-        if let Some(layer) = self.project().layer_of(focus) {
+        if let Some(layer) = self
+            .behavior
+            .creation
+            .pending_layer()
+            .or_else(|| self.project().layer_of(focus))
+        {
             self.layer = layer;
             self.explorer_index = crate::explorer::Index::new(self.project(), layer);
             self.active_diagram = self.diagram_for(layer, focus);
@@ -202,7 +207,26 @@ impl App {
         } else {
             "Recovered an unsaved local copy. Choose Save as to save it; the original file and hosted model are unchanged.".into()
         };
-        self.request_lint()
+        let lint = self.request_lint();
+        if self
+            .architecture
+            .as_ref()
+            .is_some_and(architecture_authoring::State::inline)
+        {
+            Task::batch([lint, iced::widget::operation::focus("architecture-name")])
+        } else if self.page == Page::Behavior && self.behavior.source_open() {
+            Task::batch([
+                lint,
+                iced::widget::operation::focus(behavior::source_draft::NAME_INPUT),
+            ])
+        } else if self.page == Page::Behavior && self.behavior.creation.created().is_some() {
+            Task::batch([
+                lint,
+                iced::widget::operation::focus(behavior::creation::NAME_INPUT),
+            ])
+        } else {
+            lint
+        }
     }
 }
 
@@ -331,6 +355,177 @@ mod tests {
         .unwrap()
     }
 
+    async fn run_recovery_tasks(app: &mut App, task: Task<Message>) -> (usize, bool, bool) {
+        use iced::advanced::{Layout, layout, widget};
+        use iced::futures::StreamExt;
+        // Mount real inputs, with focus initially in another control. This
+        // verifies the returned operation targets the naming field by its ID.
+        let mut fields: iced::Element<'_, (), iced::Theme, ()> = iced::widget::column![
+            iced::widget::text_input("Engineering name", "Retained name")
+                .id("architecture-name")
+                .on_input(|_| ()),
+            iced::widget::text_input("Other control", "Other value")
+                .id("unrelated-field")
+                .on_input(|_| ())
+        ]
+        .into();
+        let mut tree = widget::Tree::new(fields.as_widget());
+        let node = fields.as_widget_mut().layout(
+            &mut tree,
+            &(),
+            &layout::Limits::new(iced::Size::ZERO, iced::Size::new(320., 100.)),
+        );
+        tree.children[1]
+            .state
+            .downcast_mut::<iced::widget::text_input::State<()>>()
+            .focus();
+        let mut operations = 0;
+        let mut lint_completions = 0;
+        let mut stream = iced_runtime::task::into_stream(task).expect("Recovery must still lint");
+        while let Some(action) = stream.next().await {
+            match action {
+                iced_runtime::Action::Widget(mut operation) => {
+                    operations += 1;
+                    fields.as_widget_mut().operate(
+                        &mut tree,
+                        Layout::new(&node),
+                        &(),
+                        operation.as_mut(),
+                    );
+                }
+                iced_runtime::Action::Output(message @ Message::Linted(_, _)) => {
+                    lint_completions += 1;
+                    let _ = app.update(message);
+                }
+                _ => panic!("Unexpected recovery task action"),
+            }
+        }
+        assert_eq!(
+            lint_completions, 1,
+            "Autofocus must not replace request_lint"
+        );
+        assert!(app.lint_running.is_none());
+        let focused = |index: usize| {
+            tree.children[index]
+                .state
+                .downcast_ref::<iced::widget::text_input::State<()>>()
+                .is_focused()
+        };
+        (operations, focused(0), focused(1))
+    }
+
+    fn architecture_recovery_app() -> App {
+        let mut app = App::with_project(Project::empty());
+        let _ = app.update(Message::AddDiagram);
+        let _ = app.update(Message::Architecture(architecture_authoring::Event::Start(
+            Kind::Entity,
+            Some(Position { x: 80., y: 90. }),
+        )));
+        let _ = app.update(Message::Architecture(architecture_authoring::Event::Name(
+            "Accepted team".into(),
+        )));
+        let _ = app.update(Message::Architecture(architecture_authoring::Event::Submit));
+        assert!(app.architecture.is_none());
+        app
+    }
+
+    #[tokio::test]
+    async fn checkpoint_inline_create_and_rename_restore_focus_without_changing_drafts_or_history()
+    {
+        use architecture_authoring::Event;
+        for rename in [false, true] {
+            let mut app = architecture_recovery_app();
+            let point = Position { x: 439., y: 328.2 };
+            let event = if rename {
+                Event::Rename(app.route_context().unwrap(), app.selected, point)
+            } else {
+                Event::Start(Kind::Actor, Some(point))
+            };
+            let _ = app.update(Message::Architecture(event));
+            let _ = app.update(Message::Architecture(Event::Name(
+                "  Recovered engineering name 雨  ".into(),
+            )));
+            let saved = serde_json::to_value(&app.architecture.as_ref().unwrap().saved).unwrap();
+            let snapshot = retained_snapshot(&app).with_architecture(app.architecture.as_ref());
+            let expected = snapshot.clone().restore().unwrap();
+            let checkpoint = snapshot.id;
+            let mut recovered = App::with_project(Project::empty());
+            let task = recovered.checkpoint_loaded(Ok(Arc::new(snapshot)));
+            assert_eq!(
+                run_recovery_tasks(&mut recovered, task).await,
+                (1, true, false)
+            );
+            assert_eq!(recovered.page, Page::Diagram);
+            assert!(recovered.architecture.as_ref().unwrap().inline());
+            assert_eq!(
+                serde_json::to_value(&recovered.architecture.as_ref().unwrap().saved).unwrap(),
+                saved
+            );
+            assert_eq!(recovered.project(), expected.document.project());
+            assert_eq!(recovered.document.bundle(), expected.document.bundle());
+            assert_eq!(recovered.document.revision(), expected.document.revision());
+            assert_eq!(recovered.document.can_undo(), expected.document.can_undo());
+            assert_eq!(recovered.document.can_redo(), expected.document.can_redo());
+            assert_eq!(
+                recovered.source_workspace.bundle(),
+                expected.workspace.bundle()
+            );
+            assert_eq!(recovered.recovery.restored, Some(checkpoint));
+            assert!(recovered.path.is_none());
+        }
+    }
+
+    #[tokio::test]
+    async fn checkpoint_noninline_contexts_keep_other_focus_and_still_lint() {
+        use architecture_authoring::Event;
+        for context in ["accepted", "armed", "picker", "property", "source"] {
+            let mut app = architecture_recovery_app();
+            match context {
+                "armed" => {
+                    let _ = app.update(Message::Architecture(Event::Start(Kind::Actor, None)));
+                }
+                "picker" => {
+                    let _ = app.update(Message::Architecture(Event::Existing(None)));
+                }
+                "property" => {
+                    app.draft
+                        .as_mut()
+                        .unwrap()
+                        .input("/name", "Unapplied property".into());
+                    assert!(app.draft_dirty());
+                }
+                "source" => {
+                    app.source_workspace
+                        .edit("incomplete source 雨".into(), app.source_editor.cursor());
+                    assert!(app.source_dirty());
+                }
+                _ => {}
+            }
+            let snapshot = retained_snapshot(&app).with_architecture(app.architecture.as_ref());
+            let expected = snapshot.clone().restore().unwrap();
+            let mut recovered = App::with_project(Project::empty());
+            let task = recovered.checkpoint_loaded(Ok(Arc::new(snapshot)));
+            assert_eq!(
+                run_recovery_tasks(&mut recovered, task).await,
+                (0, false, true),
+                "{context}"
+            );
+            assert!(
+                !recovered
+                    .architecture
+                    .as_ref()
+                    .is_some_and(architecture_authoring::State::inline)
+            );
+            assert_eq!(recovered.project(), expected.document.project());
+            assert_eq!(recovered.document.bundle(), expected.document.bundle());
+            assert_eq!(recovered.document.revision(), expected.document.revision());
+            assert_eq!(
+                recovered.source_workspace.bundle(),
+                expected.workspace.bundle()
+            );
+        }
+    }
+
     #[test]
     fn saving_an_older_snapshot_keeps_recovery_for_newer_unsaved_work() {
         let directory = tempfile::tempdir().unwrap();

crates/oa-desktop/src/app/diagram_focus_tests.rs

@@ -0,0 +1,156 @@
+//! Keyboard ownership is exercised on the mounted App, not raw Canvas Program.
+use super::*;
+use crate::behavior::canvas_workspace::tests::{Mounted, key};
+use iced::advanced::widget::{Operation, operation};
+use iced::{Point, Rectangle, Size, Vector, keyboard::key::Named, mouse};
+
+struct FocusField(Rectangle);
+impl Operation for FocusField {
+    fn traverse(&mut self, visit: &mut dyn FnMut(&mut dyn Operation)) {
+        visit(self);
+    }
+    fn focusable(
+        &mut self,
+        _: Option<&iced::advanced::widget::Id>,
+        bounds: Rectangle,
+        state: &mut dyn operation::Focusable,
+    ) {
+        if bounds == self.0 {
+            state.focus();
+        } else {
+            state.unfocus();
+        }
+    }
+}
+
+async fn f2(mounted: &mut Mounted, app: &mut App) -> Vec<Message> {
+    mounted
+        .batch(app, &[key(Named::F2)], mouse::Cursor::Unavailable)
+        .await
+}
+
+fn rename_emitted(messages: &[Message]) -> bool {
+    messages.iter().any(|message| {
+        matches!(
+            message,
+            Message::Architecture(architecture_authoring::Event::Rename(..))
+        )
+    })
+}
+
+#[tokio::test]
+async fn mounted_f2_requires_canvas_focus_and_yields_to_clean_inspector() {
+    for layer in [Layer::Oa, Layer::Sa] {
+        for programmatic in [true, false] {
+            let mut project = Project::empty();
+            let object = project
+                .add_element(
+                    if layer == Layer::Oa {
+                        Kind::Entity
+                    } else {
+                        Kind::System
+                    },
+                    layer,
+                    "Original team",
+                    None,
+                )
+                .unwrap();
+            let diagram = project.ensure_diagram(layer);
+            project.diagrams.get_mut(&diagram).unwrap().projection = ProjectionKind::Overview;
+            let node = project.place(diagram, object, Position { x: 80., y: 80. });
+            let mut app = App::with_project(project);
+            app.page = Page::Diagram;
+            app.layer = layer;
+            app.active_diagram = Some(diagram);
+            app.window_size = Size::new(2000., 1400.);
+            let _ = app.update(Message::Select(object));
+            let before = app.document.snapshot();
+            let mut mounted = Mounted::new(&mut app).await;
+            app.zoom = 1.;
+            app.pan = Vector::ZERO;
+            app.fit_to_view = false;
+            mounted.settle(&mut app).await;
+
+            // Selection alone does not grant the canvas keyboard ownership.
+            assert!(!rename_emitted(&f2(&mut mounted, &mut app).await));
+            assert!(app.architecture.is_none());
+            assert_eq!(app.document.bundle(), &before.bundle);
+
+            let bounds = mounted
+                .geometry(&app)
+                .bounds(crate::allocation_input::CANVAS_ID);
+            let projected = projection::project_view(app.project(), diagram)
+                .nodes
+                .into_iter()
+                .find(|item| item.id == node)
+                .unwrap();
+            let point = Point::new(
+                bounds.x + projected.position.x + 40.,
+                bounds.y + projected.position.y + 35.,
+            );
+            mounted.click(&mut app, point).await;
+            assert_eq!((app.selected, app.selected_node), (object, Some(node)));
+            assert!(rename_emitted(&f2(&mut mounted, &mut app).await));
+            let rename = app.architecture.as_ref().expect("canvas F2 opens rename");
+            assert!(rename.inline());
+            assert!(matches!(
+                &rename.saved.intent,
+                architecture_authoring::Intent::Rename { element, name }
+                    if *element == object && name == "Original team"
+            ));
+            assert_eq!(app.document.bundle(), &before.bundle);
+            assert!(
+                !app.document.can_undo(),
+                "opening rename is not a model edit"
+            );
+
+            let task = app.update(Message::Escape);
+            mounted.perform(&mut app, task).await;
+            assert!(app.architecture.is_none());
+            mounted.click(&mut app, point).await;
+            let field = mounted
+                .geometry(&app)
+                .text_inputs
+                .into_iter()
+                .filter(|bounds| bounds.x > app.window_size.width - 320.)
+                .min_by(|a, b| a.y.total_cmp(&b.y))
+                .expect("Inspector name field is mounted");
+            if programmatic {
+                mounted.operate(&app, &mut FocusField(field));
+            } else {
+                let messages = mounted
+                    .batch(
+                        &mut app,
+                        &[key(Named::Tab), key(Named::F2)],
+                        mouse::Cursor::Unavailable,
+                    )
+                    .await;
+                assert!(
+                    !rename_emitted(&messages),
+                    "Tab must retire F2 admission before its queued focus task"
+                );
+            }
+            let geometry = mounted.geometry(&app);
+            assert!(
+                geometry
+                    .focused
+                    .iter()
+                    .any(|(_, bounds, focused)| { *bounds == field && *focused })
+            );
+            assert!(geometry.focused.iter().any(|(id, _, focused)| {
+                id.as_ref() == Some(&iced::advanced::widget::Id::from("diagram-keyboard-owner"))
+                    && !*focused
+            }));
+            assert!(!app.draft_dirty(), "the Inspector is still clean");
+            assert!(!rename_emitted(&f2(&mut mounted, &mut app).await));
+            assert!(app.architecture.is_none());
+            assert_eq!(
+                app.draft.as_ref().unwrap().inputs["/name"].raw,
+                "Original team"
+            );
+            assert_eq!(app.project(), &before.decoded.project);
+            assert_eq!(app.document.bundle(), &before.bundle);
+            assert!(!app.document.can_undo());
+        }
+    }
+}

crates/oa-desktop/src/app/diagram_removal.rs

@@ -0,0 +1,240 @@
+//! Captured diagram removal and model-confirmation lifetimes.
+use super::*;
+use crate::{model_menu, route_edit::Context};
+
+#[derive(Debug, Clone)]
+pub struct Intent {
+    pub context: Context,
+    pub object: Id,
+    pub placement: Option<Id>,
+    pub model: bool,
+}
+
+pub struct Confirmation {
+    pub snapshot: model_menu::Opened,
+    pub selection: Id,
+    pub placement: Option<Id>,
+    pub behavior_owner: Option<Id>,
+}
+
+pub fn enabled(app: &App) -> bool {
+    !app.busy && focus_enabled(app)
+}
+
+pub(crate) fn focus_enabled(app: &App) -> bool {
+    crate::behavior::canvas_workspace::keyboard_owner_enabled(app)
+        && !app.draft_dirty()
+        && !app.source_dirty()
+        && !app.behavior.has_pending()
+        && app
+            .architecture
+            .as_ref()
+            .is_none_or(|state| !state.inline())
+}
+
+pub(crate) fn behavior_owner(app: &App) -> Option<Id> {
+    app.topology_context()
+        .map(|context| context.owner)
+        .or_else(|| app.scenario_context().map(|context| context.scenario))
+}
+
+fn placement(app: &App) -> Option<Id> {
+    if behavior_owner(app).is_some() {
+        None
+    } else if app.page == Page::Behavior {
+        app.behavior.diagram.placement
+    } else {
+        app.selected_node
+    }
+}
+
+/// The derived canvases remove semantic occurrences, not reusable definitions.
+/// Kept beside target capture so confirmation rendering uses the same meaning.
+pub(crate) fn explanation(app: &App, object: Id) -> &'static str {
+    if app
+        .project()
+        .diagrams
+        .values()
+        .any(|diagram| diagram.nodes.contains_key(&object))
+    {
+        return "Remove only this diagram placement. The model element and its placements in other diagrams remain. Undo restores this placement.";
+    }
+    if app
+        .project()
+        .relations
+        .get(&object)
+        .is_some_and(|relation| {
+            matches!(
+                relation.kind(),
+                RelationKind::StateAction | RelationKind::StateTransition
+            )
+        })
+    {
+        return "Remove this state relation. Its states and referenced activities or functions remain. Undo restores the relation.";
+    }
+    if app
+        .project()
+        .relations
+        .get(&object)
+        .is_some_and(|relation| {
+            matches!(
+                relation.kind(),
+                RelationKind::SequenceLink | RelationKind::ContextualLink
+            )
+        })
+    {
+        return "Remove this process link. Its endpoint occurrences and referenced reusable model elements are preserved. Undo restores the deletion.";
+    }
+    match app
+        .project()
+        .elements
+        .get(&object)
+        .and_then(|element| element.shared())
+    {
+        Some(SharedBody::Lifeline { .. }) => {
+            "Remove this participant from the scenario. Its represented model element is preserved. Messages and other occurrences remain with affected participant references cleared. Undo restores the deletion."
+        }
+        Some(SharedBody::Occurrence {
+            body: OccurrenceBody::Fragment { .. } | OccurrenceBody::Branch { .. },
+            ..
+        }) => {
+            "Remove this occurrence and its owned branches and steps. Referenced reusable model elements are preserved. Undo restores the deletion."
+        }
+        Some(SharedBody::Occurrence { .. }) => {
+            "Remove this occurrence and its dependent links. Referenced reusable model elements are preserved. Undo restores the deletion."
+        }
+        _ => {
+            "Owned children, incident relations, occurrences, placements and trace links will also be removed. The traced counterpart itself is preserved. Undo restores the deletion."
+        }
+    }
+}
+
+impl App {
+    pub(super) fn remove_from_diagram(&mut self, intent: Intent) {
+        if !enabled(self) || self.connection.is_some() || self.selected_bend.is_some() {
+            return;
+        }
+        let current = match self.page {
+            Page::Diagram if self.architecture.as_ref().is_none_or(|s| !s.saved.placing) => {
+                self.route_context()
+            }
+            Page::Behavior
+                if self.behavior.diagram.tool == crate::behavior::state_edit::Tool::Select =>
+            {
+                self.state_context()
+            }
+            _ => None,
+        };
+        let selected_object = self
+            .project()
+            .diagrams
+            .get(&intent.context.diagram)
+            .and_then(|diagram| diagram.nodes.get(&self.selected))
+            .map_or(self.selected, |node| node.element);
+        if current != Some(intent.context) || selected_object != intent.object {
+            return;
+        }
+        let view = projection::project_view(self.project(), intent.context.diagram);
+        let placement = if self.page == Page::Behavior {
+            self.behavior.diagram.placement
+        } else {
+            self.selected_node
+        };
+        if intent.placement != placement || intent.object == intent.context.diagram {
+            return;
+        }
+        let visible = if let Some(id) = intent.placement {
+            self.project().diagrams[&intent.context.diagram]
+                .nodes
+                .get(&id)
+                .is_some_and(|node| node.element == intent.object)
+                && view
+                    .nodes
+                    .iter()
+                    .any(|node| node.id == id && node.element == intent.object)
+        } else {
+            view.edges.iter().any(|edge| edge.id == intent.object)
+                || view.ports.iter().any(|port| port.element == intent.object)
+                || (self.page == Page::Behavior
+                    && crate::behavior::state_canvas::visible_row_relation(
+                        self.project(),
+                        intent.context.diagram,
+                        &view,
+                        intent.object,
+                    ))
+        };
+        if !visible {
+            return;
+        }
+        if !intent.model
+            && let Some(placement) = intent.placement
+        {
+            if self.execute(Command::Delete(placement)) {
+                self.selected_node = None;
+                self.behavior.diagram.placement = None;
+                self.selected_bend = None;
+                self.status = "Hidden from this diagram · Model element preserved · Undo restores the placement".into();
+            }
+        } else {
+            self.begin_model_delete_target(intent.object, Some(intent.context));
+        }
+    }
+
+    pub(super) fn begin_model_delete(&mut self, canvas: Option<Context>) {
+        self.begin_model_delete_target(self.selected, canvas);
+    }
+
+    fn begin_model_delete_target(&mut self, object: Id, canvas: Option<Context>) {
+        if object == self.project().id || self.behavior.has_pending() {
+            return;
+        }
+        let mut request = model_menu::Request::object(object, iced::Point::ORIGIN);
+        request.canvas = canvas;
+        request.placement = placement(self);
+        // Opening a modal retires any pending canvas intent before capturing
+        // the confirmation; every new dialog receives its own replay token.
+        self.canvas_epoch = self.canvas_epoch.wrapping_add(1);
+        if canvas.is_some() {
+            request.canvas = if self.page == Page::Behavior {
+                self.state_context()
+            } else {
+                self.route_context()
+            };
+        }
+        self.menu_sequence = self.menu_sequence.wrapping_add(1);
+        self.delete_target =
+            model_menu::Opened::new(self, request, self.menu_sequence).map(|snapshot| {
+                Confirmation {
+                    snapshot,
+                    selection: self.selected,
+                    placement: placement(self),
+                    behavior_owner: behavior_owner(self),
+                }
+            });
+        self.delete_pending = self.delete_target.is_some();
+    }
+
+    pub(super) fn confirm_model_delete(&mut self, token: u64) {
+        let Some(target) = self.delete_target.as_ref() else {
+            return;
+        };
+        if target.snapshot.token != token {
+            return;
+        }
+        let valid = self.delete_pending
+            && target.snapshot.valid(self)
+            && target.selection == self.selected
+            && target.placement == placement(self)
+            && target.behavior_owner == behavior_owner(self)
+            && !self.behavior.has_pending()
+            && !self.source_dirty()
+            && !self.draft_dirty();
+        let id = target.snapshot.request.object;
+        self.delete_pending = false;
+        self.delete_target = None;
+        self.canvas_epoch = self.canvas_epoch.wrapping_add(1);
+        if valid {
+            self.execute(Command::Delete(id));
+        }
+    }
+}

crates/oa-desktop/src/app/diagram_removal_tests/navigation_union.rs

@@ -0,0 +1,146 @@
+//! Navigate first, then remove through the mounted root canvas and history.
+use super::*;
+use crate::diagram_usage::{self as usage, Target};
+
+async fn navigate_then_remove(project: Project, subject: Id, owner: Id, row: bool) {
+    let mut app = App::with_project(project);
+    app.window_size = Size::new(2000., 1400.);
+    let before = app.document.snapshot();
+    let message = app.diagram_usage_message(subject);
+    let _ = app.update(message);
+    let panel = app.diagram_usages.as_ref().unwrap();
+    let token = panel.token;
+    let context = panel.context;
+    // Complete the same query independently without polling its worker Task.
+    let process = app.behavior.topology.usage_snapshot().into_query_state();
+    let completion = usage::Completion {
+        token,
+        context,
+        result: Ok(usage::collect(
+            app.project(),
+            subject,
+            &process,
+            &behavior::scenario::State::default(),
+        )),
+    };
+    let _ = app.update(Message::DiagramUsagesReady(completion));
+    let found = app
+        .diagram_usages
+        .as_ref()
+        .unwrap()
+        .usages
+        .iter()
+        .find(|usage| {
+            if row {
+                matches!(usage.target, Target::StateRow { relation, .. } if relation == subject)
+            } else {
+                matches!(usage.target, Target::Port { port, .. } if port == subject)
+            }
+        })
+        .unwrap()
+        .clone();
+    let _ = app.update(Message::DiagramUsage(usage::Event::Choose(
+        token,
+        found.clone(),
+    )));
+    assert_eq!(app.selected, subject);
+    // refresh_draft normalizes the owner's presentation placement; navigation
+    // must not leave it armed as a removal target.
+    assert!(app.selected_node.is_none());
+    assert!(app.behavior.diagram.placement.is_none());
+    assert_eq!(
+        app.diagram_focus(found.surface).unwrap().target,
+        found.target
+    );
+
+    let mut mounted = Mounted::new(&mut app).await;
+    assert_eq!(app.project(), &before.decoded.project);
+    assert_eq!(app.document.bundle(), &before.bundle);
+    assert!(app.pending_diagram_reveal.is_none());
+    for model in [false, true] {
+        mounted
+            .perform(
+                &mut app,
+                iced::widget::operation::focus(iced::advanced::widget::Id::from(
+                    "diagram-keyboard-owner",
+                )),
+            )
+            .await;
+        let messages = delete(&mut mounted, &mut app, model).await;
+        let request = messages
+            .iter()
+            .find_map(|message| match message {
+                Message::DiagramRemove(intent)
+                | Message::StateDiagram(behavior::state_edit::Event::Remove(intent)) => {
+                    Some(intent)
+                }
+                _ => None,
+            })
+            .expect("actual focused canvas emitted a removal intent");
+        assert_eq!(request.object, subject);
+        assert_eq!(request.placement, None);
+        assert_eq!(request.model, model);
+        assert_eq!(
+            app.delete_target.as_ref().unwrap().snapshot.request.object,
+            subject
+        );
+        assert_eq!(app.project(), &before.decoded.project);
+        assert_eq!(app.document.bundle(), &before.bundle);
+        if !model {
+            let task = app.update(Message::CancelDelete);
+            mounted.perform(&mut app, task).await;
+        }
+    }
+    let token = app.delete_target.as_ref().unwrap().snapshot.token;
+    let task = app.update(Message::ConfirmDelete(token));
+    mounted.perform(&mut app, task).await;
+    let expected = execute_batch(&before.decoded.project, &[Command::Delete(subject)]).unwrap();
+    assert_eq!(app.project(), &expected);
+    assert!(app.project().contains(owner));
+    consistent(&app);
+    let task = app.update(Message::Undo);
+    mounted.perform(&mut app, task).await;
+    assert_eq!(app.project(), &before.decoded.project);
+    assert_eq!(app.document.bundle(), &before.bundle);
+    assert!(!app.document.can_undo());
+}
+
+#[tokio::test]
+async fn port_navigation_then_canvas_delete_preserves_owner_and_restores_exact_history() {
+    let mut project = Project::empty();
+    let owner = project.add(Kind::Function, "Compute", 1200., 1500.);
+    let port = Id::new_v4();
+    let element = oa_core::ports::make_port(
+        &project,
+        port,
+        owner,
+        "Input",
+        oa_core::PortContract::FunctionInput {
+            incoming_items: vec![],
+        },
+    )
+    .unwrap();
+    project = execute_batch(&project, &[Command::CreateElement(element)]).unwrap();
+    navigate_then_remove(project, port, owner, false).await;
+}
+
+#[tokio::test]
+async fn state_row_navigation_then_canvas_delete_preserves_work_and_restores_exact_history() {
+    let mut project = Project::empty();
+    let machine = project
+        .add_element(Kind::StateMachine, Layer::Sa, "Modes", None)
+        .unwrap();
+    let region = project
+        .add_element(Kind::Region, Layer::Sa, "Main", Some(machine))
+        .unwrap();
+    let state = project
+        .add_element(Kind::State, Layer::Sa, "Running", Some(region))
+        .unwrap();
+    let work = project
+        .add_element(Kind::Function, Layer::Sa, "Monitor", None)
+        .unwrap();
+    let relation = project.relate(RelationKind::StateAction, "Entry", state, work);
+    let plan = crate::behavior::state_edit::create_view(&project, machine).unwrap();
+    project = execute_batch(&project, &[plan.command]).unwrap();
+    navigate_then_remove(project, relation, work, true).await;
+}

crates/oa-desktop/src/app/diagram_reveal.rs

@@ -0,0 +1,161 @@
+//! Complete a navigation camera after the destination reports its real viewport.
+use super::*;
+use crate::behavior::scenario_layout::Representation;
+use crate::diagram_usage::{Context, Surface};
+#[cfg(test)]
+mod tests;
+
+impl App {
+    pub(super) fn is_diagram_viewport(message: &Message) -> bool {
+        matches!(
+            message,
+            Message::CanvasResized(_)
+                | Message::DiagramRevealViewport(..)
+                | Message::TopologyCanvas(behavior::topology::CanvasEvent::Viewport(..))
+                | Message::ScenarioCanvas(behavior::scenario::CanvasEvent::Viewport(..))
+                | Message::StateDiagram(behavior::state_edit::Event::Viewport(..))
+        )
+    }
+    pub(crate) fn architecture_reveal_stamp(&self, diagram: Id) -> Option<(Context, u64)> {
+        self.pending_diagram_reveal
+            .as_ref()
+            .filter(|(_, u, _)| u.surface == Surface::Saved(diagram))
+            .map(|(context, _, epoch)| (*context, *epoch))
+    }
+
+    pub(super) fn diagram_reveal_viewport(&self, message: &Message) -> Option<Surface> {
+        let (context, usage, epoch) = self.pending_diagram_reveal.as_ref()?;
+        if context.document != self.canvas_document
+            || context.revision != self.document.revision()
+            || *epoch != self.canvas_epoch
+        {
+            return None;
+        }
+        let (surface, size, valid) = match message {
+            Message::DiagramRevealViewport(c, e, size) => (
+                usage.surface,
+                *size,
+                c == context
+                    && e == epoch
+                    && self.page == Page::Diagram
+                    && Some(usage.surface.id()) == self.active_diagram,
+            ),
+            Message::TopologyCanvas(behavior::topology::CanvasEvent::Viewport(c, size)) => (
+                Surface::Process(c.owner),
+                *size,
+                c.document == context.document
+                    && c.revision == context.revision
+                    && c.epoch == *epoch,
+            ),
+            Message::ScenarioCanvas(behavior::scenario::CanvasEvent::Viewport(c, size)) => (
+                match c.representation {
+                    Representation::Derived { owner } => Surface::Scenario(owner),
+                    Representation::Saved { diagram } => Surface::Saved(diagram),
+                },
+                *size,
+                c.document == context.document
+                    && c.revision == context.revision
+                    && c.epoch == *epoch
+                    && self.pending_scenario_reveal_visit == Some(c.visit)
+                    && self.page == Page::Behavior
+                    && self.behavior.active_owner == Some(c.scenario)
+                    && self.behavior.scenario.context(
+                        self.canvas_document,
+                        c.scenario,
+                        self.document.revision(),
+                        self.canvas_epoch,
+                    ) == Some(*c),
+            ),
+            Message::StateDiagram(behavior::state_edit::Event::Viewport(c, size)) => (
+                Surface::Saved(c.diagram),
+                *size,
+                c.document == context.document
+                    && c.revision == context.revision
+                    && c.epoch == *epoch,
+            ),
+            _ => return None,
+        };
+        (valid
+            && surface == usage.surface
+            && size.width.is_finite()
+            && size.height.is_finite()
+            && size.width > 0.
+            && size.height > 0.)
+            .then_some(surface)
+    }
+
+    pub(super) fn reconcile_pending_diagram_reveal(&mut self, message: &Message) {
+        if !matches!(
+            message,
+            Message::CheckpointTick
+                | Message::CheckpointWritten(..)
+                | Message::Lint(_)
+                | Message::Linted(..)
+                | Message::SourceViewport(_)
+                | Message::WindowResized(_)
+                | Message::CanvasResized(_)
+                | Message::DiagramRevealViewport(..)
+                | Message::DiagramUsage(_)
+                | Message::DiagramUsagesReady(_)
+                | Message::SourceSymbolsReady(_)
+                | Message::SourceRenameReady(_)
+                | Message::WorkDrag(allocation_drag::Event::KeyboardBoundary)
+                | Message::WorkDrag(allocation_drag::Event::Unfocused)
+                | Message::TopologyCanvas(behavior::topology::CanvasEvent::Viewport(..))
+                | Message::ScenarioCanvas(behavior::scenario::CanvasEvent::Viewport(..))
+                | Message::StateDiagram(behavior::state_edit::Event::Viewport(..))
+        ) {
+            self.pending_diagram_reveal = None;
+            self.pending_scenario_reveal_visit = None;
+            if !Self::is_navigation_camera(message) {
+                self.diagram_navigation_focus = None;
+            }
+        }
+    }
+
+    fn is_navigation_camera(message: &Message) -> bool {
+        if let Message::BehaviorControl(intent) = message {
+            return Self::is_navigation_camera(&intent.message);
+        }
+        matches!(
+            message,
+            Message::Pan(_)
+                | Message::Zoom(_)
+                | Message::Fit
+                | Message::TopologyCanvas(
+                    behavior::topology::CanvasEvent::Camera(..)
+                        | behavior::topology::CanvasEvent::Zoom(..)
+                        | behavior::topology::CanvasEvent::Scrolled(..)
+                )
+                | Message::ScenarioCanvas(
+                    behavior::scenario::CanvasEvent::Camera(..)
+                        | behavior::scenario::CanvasEvent::Zoom(..)
+                        | behavior::scenario::CanvasEvent::Scrolled(..)
+                )
+                | Message::StateDiagram(
+                    behavior::state_edit::Event::Pan(..)
+                        | behavior::state_edit::Event::Zoom(..)
+                        | behavior::state_edit::Event::Fit(..)
+                )
+        )
+    }
+
+    pub(super) fn finish_diagram_reveal(&mut self, surface: Surface) {
+        let Some((context, usage, _)) = self.pending_diagram_reveal.take() else {
+            return;
+        };
+        if context.document == self.canvas_document
+            && context.revision == self.document.revision()
+            && usage.surface == surface
+            && !self.draft_dirty()
+            && !self.source_dirty()
+            && !self.behavior.has_pending()
+        {
+            // The normal viewport handler has now stored the measured size.
+            // Target identity was validated for this revision before navigation.
+            self.reveal_diagram_usage(&usage);
+        }
+        self.pending_diagram_reveal = None;
+        self.pending_scenario_reveal_visit = None;
+    }
+}

crates/oa-desktop/src/app/diagram_reveal/tests.rs

@@ -0,0 +1,418 @@
+//! Independent first-layout navigation oracles, through the real App boundary.
+use super::*;
+use crate::diagram_usage::{self as usage, Target, Usage};
+use iced::{Size, Vector};
+use std::collections::BTreeMap;
+
+#[derive(Clone, Copy, Debug)]
+enum Canvas {
+    Architecture,
+    Process,
+    Scenario,
+    State,
+}
+const CANVASES: [Canvas; 4] = [
+    Canvas::Architecture,
+    Canvas::Process,
+    Canvas::Scenario,
+    Canvas::State,
+];
+const WIDE: Size = Size::new(1200., 700.);
+const ACTUAL: Size = Size::new(500., 300.);
+
+fn send(app: &mut App, message: Message) {
+    let _ = app.update(message);
+}
+
+fn fixture(canvas: Canvas) -> (App, Usage) {
+    let mut p = Project::empty();
+    let work = p
+        .add_element(Kind::Activity, Layer::Oa, "Respond", None)
+        .unwrap();
+    let (surface, subject) = match canvas {
+        Canvas::Architecture => {
+            let diagram = p.ensure_diagram(Layer::Oa);
+            p.place(
+                diagram,
+                work,
+                Position {
+                    x: 12_000.,
+                    y: 9_000.,
+                },
+            );
+            (Surface::Saved(diagram), work)
+        }
+        Canvas::Process | Canvas::Scenario => {
+            let kind = if matches!(canvas, Canvas::Process) {
+                Kind::Process
+            } else {
+                Kind::Scenario
+            };
+            let owner = p.add_element(kind, Layer::Oa, "Response", None).unwrap();
+            let occurrence = p
+                .add_element(Kind::Occurrence, Layer::Oa, "Respond here", Some(owner))
+                .unwrap();
+            *p.elements
+                .get_mut(&occurrence)
+                .unwrap()
+                .shared_mut()
+                .unwrap() = SharedBody::Occurrence {
+                body: OccurrenceBody::Action {
+                    action: Some(work),
+                    lifeline: None,
+                },
+                precondition: String::new(),
+                postcondition: String::new(),
+            };
+            let steps = p.elements.get_mut(&owner).unwrap().steps_mut().unwrap();
+            if !steps.contains(&occurrence) {
+                steps.push(occurrence);
+            }
+            (
+                if matches!(canvas, Canvas::Process) {
+                    Surface::Process(owner)
+                } else {
+                    Surface::Scenario(owner)
+                },
+                occurrence,
+            )
+        }
+        Canvas::State => {
+            let machine = p
+                .add_element(Kind::StateMachine, Layer::Oa, "Modes", None)
+                .unwrap();
+            let region = p
+                .add_element(Kind::Region, Layer::Oa, "Main", Some(machine))
+                .unwrap();
+            let state = p
+                .add_element(Kind::State, Layer::Oa, "Ready", Some(region))
+                .unwrap();
+            let diagram = Id::new_v4();
+            p.diagrams.insert(
+                diagram,
+                Diagram {
+                    id: diagram,
+                    alias: "ready_view".into(),
+                    name: "Ready view".into(),
+                    description: String::new(),
+                    layer: Layer::Oa,
+                    projection: ProjectionKind::StateMachine { machine },
+                    nodes: BTreeMap::new(),
+                    layout: None,
+                    routes: vec![],
+                    view_options: Default::default(),
+                },
+            );
+            p.place(
+                diagram,
+                state,
+                Position {
+                    x: 8_000.,
+                    y: 11_000.,
+                },
+            );
+            (Surface::Saved(diagram), state)
+        }
+    };
+    let mut app = App::with_project(p);
+    let found = usage::collect(
+        app.project(),
+        subject,
+        &app.behavior.topology,
+        &app.behavior.scenario,
+    )
+    .into_iter()
+    .find(|u| u.surface == surface && u.target != Target::Whole)
+    .unwrap();
+    app.canvas_size = Some(WIDE);
+    app.behavior.diagram.viewport = Some(WIDE);
+    if let Surface::Process(owner) = surface {
+        app.behavior.topology.enter(app.canvas_document, owner);
+        app.behavior.topology.viewport(WIDE);
+    }
+    if let Surface::Scenario(owner) = surface {
+        app.behavior.scenario.enter(app.canvas_document, owner);
+        app.behavior.scenario.viewport(WIDE);
+    }
+    app.page = Page::Text;
+    (app, found)
+}
+
+fn measurement(
+    canvas: Canvas,
+    context: Context,
+    epoch: u64,
+    surface: Surface,
+    size: Size,
+    visit: Id,
+) -> Message {
+    match canvas {
+        Canvas::Architecture => Message::DiagramRevealViewport(context, epoch, size),
+        Canvas::Process => Message::TopologyCanvas(behavior::topology::CanvasEvent::Viewport(
+            behavior::topology::Context {
+                document: context.document,
+                owner: surface.id(),
+                revision: context.revision,
+                epoch,
+            },
+            size,
+        )),
+        Canvas::Scenario => Message::ScenarioCanvas(behavior::scenario::CanvasEvent::Viewport(
+            behavior::scenario::Context {
+                document: context.document,
+                scenario: surface.id(),
+                representation: Representation::Derived {
+                    owner: surface.id(),
+                },
+                visit,
+                revision: context.revision,
+                epoch,
+            },
+            size,
+        )),
+        Canvas::State => Message::StateDiagram(behavior::state_edit::Event::Viewport(
+            behavior::state_edit::Context {
+                document: context.document,
+                diagram: surface.id(),
+                revision: context.revision,
+                epoch,
+            },
+            size,
+        )),
+    }
+}
+
+fn stamp(app: &App) -> (Context, u64, Id) {
+    let (context, _, epoch) = app
+        .pending_diagram_reveal
+        .as_ref()
+        .expect("reveal awaits measured destination");
+    (
+        *context,
+        *epoch,
+        app.pending_scenario_reveal_visit.unwrap_or(Id::nil()),
+    )
+}
+
+fn assert_centered(app: &App, canvas: Canvas, target: &Usage) {
+    // All independently authored fixture targets fit ACTUAL at the readable cap.
+    // This oracle does not call the production camera/reveal implementation.
+    let zoom = 1.25;
+    let pan = Vector::new(
+        250. - target.bounds.center_x() * zoom,
+        150. - target.bounds.center_y() * zoom,
+    );
+    match canvas {
+        Canvas::Architecture => {
+            assert_eq!(app.canvas_size, Some(ACTUAL));
+            assert_eq!(app.zoom, zoom);
+            assert_eq!(app.pan, pan);
+            assert!(!app.fit_to_view);
+        }
+        Canvas::State => {
+            assert_eq!(app.behavior.diagram.viewport, Some(ACTUAL));
+            assert_eq!(app.behavior.diagram.zoom, zoom);
+            assert_eq!(app.behavior.diagram.pan, pan);
+            assert!(!app.behavior.diagram.fit);
+        }
+        Canvas::Process => {
+            let mut expected = behavior::topology::State::default();
+            expected.enter(app.canvas_document, target.surface.id());
+            expected.viewport(ACTUAL);
+            expected.zoom(Some(zoom));
+            expected.camera(behavior::canvas_workspace::Event::Pan(pan));
+            assert!(app.behavior.topology.camera_boundary() == expected.camera_boundary());
+        }
+        Canvas::Scenario => {
+            let mut expected = behavior::scenario::State::default();
+            expected.enter(app.canvas_document, target.surface.id());
+            expected.choose_tool(target.surface.id(), behavior::scenario::CanvasTool::Select);
+            expected.viewport(ACTUAL);
+            expected.zoom(Some(zoom));
+            expected.camera(
+                app.project(),
+                target.surface.id(),
+                behavior::canvas_workspace::Event::Pan(pan),
+            );
+            assert!(app.behavior.scenario.camera_boundary() == expected.camera_boundary());
+        }
+    }
+}
+
+#[test]
+fn all_reveal_surfaces_recenter_once_after_the_real_viewport_and_preserve_authored_state() {
+    for canvas in CANVASES {
+        let (mut app, target) = fixture(canvas);
+        let accepted = app.document.snapshot();
+        let drafts = app.source_workspace.bundle();
+        let revision = app.document.revision();
+        let history = (
+            app.document.can_undo(),
+            app.document.can_redo(),
+            app.document.dirty(),
+        );
+        assert!(app.reveal_diagram_usage(&target));
+        let (context, epoch, visit) = stamp(&app);
+        send(
+            &mut app,
+            measurement(canvas, context, epoch, target.surface, ACTUAL, visit),
+        );
+        assert!(app.pending_diagram_reveal.is_none());
+        assert_centered(&app, canvas, &target);
+        assert!(Arc::ptr_eq(&accepted, &app.document.snapshot()));
+        assert_eq!(app.source_workspace.bundle(), drafts);
+        assert_eq!(app.document.revision(), revision);
+        assert_eq!(
+            (
+                app.document.can_undo(),
+                app.document.can_redo(),
+                app.document.dirty()
+            ),
+            history
+        );
+        // The exact delivered callback is a replay after the one-shot is consumed.
+        let camera = app.camera_boundary();
+        send(
+            &mut app,
+            measurement(canvas, context, epoch, target.surface, ACTUAL, visit),
+        );
+        assert!(app.pending_diagram_reveal.is_none());
+        assert!(app.camera_boundary() == camera);
+        assert_centered(&app, canvas, &target);
+    }
+}
+
+#[test]
+fn malformed_or_wrong_stamp_measurements_cannot_poison_a_pending_reveal() {
+    for canvas in CANVASES {
+        for invalid in 0..6 {
+            let (mut app, target) = fixture(canvas);
+            assert!(app.reveal_diagram_usage(&target));
+            let (context, epoch, visit) = stamp(&app);
+            let camera = app.camera_boundary();
+            let mut stale = context;
+            let mut wrong_epoch = epoch;
+            let mut size = Size::new(111., 122.);
+            match invalid {
+                0 => stale.document = Id::new_v4(),
+                1 => stale.revision = stale.revision.wrapping_add(1),
+                2 => wrong_epoch = wrong_epoch.wrapping_add(1),
+                3 => size.width = f32::NAN,
+                4 => size.height = f32::INFINITY,
+                _ => size.width = 0.,
+            }
+            send(
+                &mut app,
+                measurement(canvas, stale, wrong_epoch, target.surface, size, visit),
+            );
+            assert!(
+                app.pending_diagram_reveal.is_some(),
+                "{canvas:?} invalid case {invalid}"
+            );
+            assert_eq!(stamp(&app), (context, epoch, visit));
+            assert_eq!(app.canvas_epoch, epoch);
+            assert!(
+                app.camera_boundary() == camera,
+                "{canvas:?} invalid case {invalid}"
+            );
+            send(
+                &mut app,
+                measurement(canvas, context, epoch, target.surface, ACTUAL, visit),
+            );
+            assert!(app.pending_diagram_reveal.is_none());
+            assert_centered(&app, canvas, &target);
+        }
+    }
+}
+
+#[test]
+fn actual_window_resize_before_first_measurement_retains_focus_for_the_new_context() {
+    for canvas in CANVASES {
+        let (mut app, target) = fixture(canvas);
+        let accepted = app.document.snapshot();
+        assert!(app.reveal_diagram_usage(&target));
+        let (context, old_epoch, visit) = stamp(&app);
+        send(&mut app, Message::WindowResized(Size::new(1100., 700.)));
+        let (current, epoch, current_visit) = stamp(&app);
+        assert_eq!(current_visit, visit);
+        assert_eq!(current, context);
+        assert_eq!(epoch, app.canvas_epoch);
+        if matches!(canvas, Canvas::Process | Canvas::Scenario) {
+            assert_ne!(epoch, old_epoch);
+            let camera = app.camera_boundary();
+            send(
+                &mut app,
+                measurement(canvas, context, old_epoch, target.surface, ACTUAL, visit),
+            );
+            assert_eq!(stamp(&app), (current, epoch, visit));
+            assert!(app.camera_boundary() == camera);
+        }
+        send(
+            &mut app,
+            measurement(canvas, current, epoch, target.surface, ACTUAL, visit),
+        );
+        assert!(app.pending_diagram_reveal.is_none());
+        assert_centered(&app, canvas, &target);
+        assert!(Arc::ptr_eq(&accepted, &app.document.snapshot()));
+    }
+}
+
+#[test]
+fn user_camera_edit_and_navigation_cancel_deferred_focus_without_late_snapping() {
+    for canvas in CANVASES {
+        for action in 0..3 {
+            let (mut app, target) = fixture(canvas);
+            let accepted = app.document.snapshot();
+            assert!(app.reveal_diagram_usage(&target));
+            let (context, epoch, visit) = stamp(&app);
+            let event = match action {
+                0 => match canvas {
+                    Canvas::Architecture => Message::Pan(Vector::new(31., -17.)),
+                    Canvas::State => Message::StateDiagram(behavior::state_edit::Event::Pan(
+                        app.state_context().unwrap(),
+                        Vector::new(31., -17.),
+                    )),
+                    Canvas::Process => {
+                        Message::TopologyCanvas(behavior::topology::CanvasEvent::Camera(
+                            app.topology_context().unwrap(),
+                            app.camera_epoch,
+                            behavior::canvas_workspace::Event::Pan(Vector::new(31., -17.)),
+                        ))
+                    }
+                    Canvas::Scenario => {
+                        Message::ScenarioCanvas(behavior::scenario::CanvasEvent::Camera(
+                            app.scenario_context().unwrap(),
+                            app.camera_epoch,
+                            behavior::canvas_workspace::Event::Pan(Vector::new(31., -17.)),
+                        ))
+                    }
+                },
+                1 => Message::Field("/name".into(), "Pending title edit".into()),
+                _ => Message::Page(Page::Catalog),
+            };
+            send(&mut app, event);
+            assert!(
+                app.pending_diagram_reveal.is_none(),
+                "{canvas:?} action {action}"
+            );
+            let camera = app.camera_boundary();
+            let page = app.page;
+            // A stale layout callback at the already retained size cannot
+            // restore the old navigation camera after deliberate user input.
+            send(
+                &mut app,
+                measurement(canvas, context, epoch, target.surface, WIDE, visit),
+            );
+            assert!(app.pending_diagram_reveal.is_none());
+            assert!(
+                app.camera_boundary() == camera,
+                "{canvas:?} action {action}"
+            );
+            assert_eq!(app.page, page);
+            assert!(Arc::ptr_eq(&accepted, &app.document.snapshot()));
+            if action == 1 {
+                assert!(app.draft_dirty());
+            }
+        }
+    }
+}

crates/oa-desktop/src/app/diagram_usages.rs

@@ -0,0 +1,540 @@
+//! Navigation-only adapter: validates destinations before changing presentation.
+use super::*;
+use crate::behavior::scenario_layout::{Representation, presentation};
+use crate::diagram_usage::{self as usage, Context, Event, Panel, Surface, Target, Usage};
+#[cfg(test)]
+mod tests;
+
+impl App {
+    pub(crate) fn diagram_usage_message(&self, subject: Id) -> Message {
+        Message::DiagramUsage(Event::Open(Context {
+            document: self.canvas_document,
+            revision: self.document.revision(),
+            subject,
+        }))
+    }
+
+    fn usage_navigation_available(&self) -> bool {
+        !self.busy
+            && !self.source_rename.open()
+            && self.pending.is_none()
+            && self.file_prompt.is_none()
+            && !self.delete_pending
+            && self.workflow.is_none()
+            && !self.hosted.visible
+            && self.architecture.is_none()
+            && !self.reference_input_active()
+            && !self.behavior.has_pending()
+            && !self.draft_dirty()
+            && !self.source_dirty()
+    }
+
+    /// Admit at most one expensive lookup, including one accepted Project clone.
+    /// A replacement panel waits for the previous worker's exact completion.
+    fn start_diagram_lookup(&mut self) -> Task<Message> {
+        let Some(panel) = self.diagram_usages.as_ref() else {
+            return Task::none();
+        };
+        if !panel.loading || self.diagram_lookup_in_flight.is_some() {
+            return Task::none();
+        }
+        let (token, context) = (panel.token, panel.context);
+        if context.document != self.canvas_document
+            || context.revision != self.document.revision()
+            || !self.usage_navigation_available()
+        {
+            let panel = self.diagram_usages.as_mut().unwrap();
+            panel.loading = false;
+            panel.notice = Some(
+                "The model or pending edits changed. Reopen diagram navigation when ready.".into(),
+            );
+            return Task::none();
+        }
+        let project = self.project().clone();
+        let presentation = self.behavior.topology.usage_snapshot();
+        self.diagram_lookup_in_flight = Some(token);
+        Task::perform(
+            async move {
+                let result = tokio::task::spawn_blocking(move || {
+                    let process = presentation.into_query_state();
+                    let scenario = behavior::scenario::State::default();
+                    usage::collect(&project, context.subject, &process, &scenario)
+                })
+                .await
+                .map_err(|error| format!("Diagram lookup failed: {error}. Close and try again."));
+                usage::Completion {
+                    token,
+                    context,
+                    result,
+                }
+            },
+            Message::DiagramUsagesReady,
+        )
+    }
+
+    fn refresh_diagram_lookup(&mut self, notice: &str) -> Task<Message> {
+        let Some(panel) = self.diagram_usages.as_mut() else {
+            return Task::none();
+        };
+        panel.token = Id::new_v4();
+        panel.context.revision = self.document.revision();
+        panel.usages.clear();
+        panel.loading = true;
+        panel.page = 0;
+        panel.cursor = 0;
+        panel.destination = None;
+        panel.notice = Some(notice.into());
+        self.start_diagram_lookup()
+    }
+
+    /// Must run before modal/input dispatch. A closed or replaced panel still
+    /// owns its worker slot until this exact completion arrives.
+    pub(super) fn diagram_usages_ready(&mut self, completion: usage::Completion) -> Task<Message> {
+        if self.diagram_lookup_in_flight != Some(completion.token) {
+            return Task::none();
+        }
+        self.diagram_lookup_in_flight = None;
+        let Some(panel) = self.diagram_usages.as_ref() else {
+            return Task::none();
+        };
+        if panel.context.document != self.canvas_document {
+            self.diagram_usages = None;
+            return Task::none();
+        }
+        if panel.context.revision != self.document.revision() {
+            return self
+                .refresh_diagram_lookup("The model changed. Review the refreshed destinations.");
+        }
+        if panel.token != completion.token {
+            // A newer Open/refresh waited without cloning or spawning a second job.
+            return self.start_diagram_lookup();
+        }
+        let panel = self.diagram_usages.as_mut().unwrap();
+        if panel.context != completion.context || !panel.loading {
+            panel.loading = false;
+            panel.notice = Some(
+                "This lookup no longer matches the requested model. Close and try again.".into(),
+            );
+            return Task::none();
+        }
+        panel.loading = false;
+        match completion.result {
+            Ok(usages) => panel.usages = usages,
+            Err(error) => panel.notice = Some(error),
+        }
+        Task::none()
+    }
+
+    /// Selection validates one destination only; opening the chooser does the
+    /// whole-project scan on its worker, never on the GUI thread.
+    fn current_surface_usages(&self, subject: Id, surface: Surface) -> Vec<Usage> {
+        match surface {
+            Surface::Saved(diagram) => {
+                usage::saved_usages_for(self.project(), subject, Some(diagram))
+            }
+            Surface::Process(owner) => {
+                self.behavior
+                    .topology
+                    .diagram_usages(self.project(), owner, subject)
+            }
+            Surface::Scenario(owner) => {
+                self.behavior
+                    .scenario
+                    .diagram_usages(self.project(), owner, subject)
+            }
+        }
+    }
+
+    pub(super) fn diagram_usage_envelope(&self, event: &Event) -> bool {
+        match event {
+            Event::Open(context) => {
+                context.document == self.canvas_document
+                    && context.revision == self.document.revision()
+                    && self.project().contains(context.subject)
+            }
+            Event::Close(token)
+            | Event::Search(token, _)
+            | Event::Page(token, _)
+            | Event::Move(token, _)
+            | Event::Activate(token)
+            | Event::Destination(token, _)
+            | Event::Choose(token, _) => self
+                .diagram_usages
+                .as_ref()
+                .is_some_and(|panel| panel.token == *token),
+        }
+    }
+
+    pub(super) fn diagram_usage_event(&mut self, event: Event) -> Task<Message> {
+        if !self.diagram_usage_envelope(&event) {
+            return Task::none();
+        }
+        if let Event::Open(context) = event {
+            if !self.usage_navigation_available() {
+                self.status = "Apply or revert pending edits before opening diagram navigation. Your inputs are retained.".into();
+                return Task::none();
+            }
+            let mut panel = Panel::new(context, Vec::new());
+            panel.loading = true;
+            let filter_id = format!("diagram-usage-filter-{}", panel.token);
+            self.diagram_usages = Some(panel);
+            self.model_menu = None;
+            // Only an accepted new chooser supersedes the previous reveal.
+            // Rejected/stale panel envelopes leave its first measurement intact.
+            self.pending_diagram_reveal = None;
+            self.pending_scenario_reveal_visit = None;
+            self.diagram_navigation_focus = None;
+            self.canvas_epoch = self.canvas_epoch.wrapping_add(1);
+            return Task::batch([
+                self.start_diagram_lookup(),
+                iced::widget::operation::focus(filter_id),
+            ]);
+        }
+        let panel = self
+            .diagram_usages
+            .as_ref()
+            .expect("admitted chooser token");
+        if matches!(event, Event::Close(_)) {
+            self.diagram_usages = None;
+            if self.page == Page::Text {
+                self.restore_source_editor_focus();
+            }
+            return Task::none();
+        }
+        if panel.context.document != self.canvas_document {
+            self.diagram_usages = None;
+            return Task::none();
+        }
+        if panel.context.revision != self.document.revision() {
+            return self
+                .refresh_diagram_lookup("The model changed. Review the refreshed destinations.");
+        }
+        if panel.loading {
+            // Search and Close remain useful while loading; queued activation
+            // must not perform a synchronous fallback or choose an old row.
+            if let Event::Search(_, query) = event {
+                self.diagram_usages.as_mut().unwrap().search = query;
+            }
+            return Task::none();
+        }
+        match event {
+            Event::Move(_, direction) => {
+                let panel = self.diagram_usages.as_ref().unwrap();
+                let count = panel.choices(self.project()).len();
+                let panel = self.diagram_usages.as_mut().unwrap();
+                if count > 0 {
+                    panel.cursor = if direction < 0 {
+                        (panel.cursor + count - 1) % count
+                    } else {
+                        (panel.cursor + 1) % count
+                    };
+                    panel.page = panel.cursor / 6;
+                }
+            }
+            Event::Activate(_) => {
+                let panel = self.diagram_usages.as_ref().unwrap();
+                if let Some(event) = panel.choices(self.project()).get(panel.cursor).cloned() {
+                    return self.diagram_usage_event(event);
+                }
+            }
+            Event::Search(_, query) => {
+                let panel = self.diagram_usages.as_mut().unwrap();
+                panel.search = query;
+                panel.page = 0;
+                panel.cursor = 0;
+            }
+            Event::Page(_, page) => {
+                let panel = self.diagram_usages.as_mut().unwrap();
+                panel.page = page;
+                panel.cursor = page.saturating_mul(6);
+            }
+            Event::Destination(_, surface) => {
+                let panel = self.diagram_usages.as_mut().unwrap();
+                if surface.is_none() || panel.usages.iter().any(|u| Some(u.surface) == surface) {
+                    panel.destination = surface;
+                    panel.page = 0;
+                    panel.cursor = 0;
+                }
+            }
+            Event::Choose(_, requested) => {
+                if !self.usage_navigation_available() {
+                    return Task::none();
+                }
+                let subject = self.diagram_usages.as_ref().unwrap().context.subject;
+                let fresh = self
+                    .current_surface_usages(subject, requested.surface)
+                    .into_iter()
+                    .find(|u| u.subject == requested.subject && u.target == requested.target);
+                let Some(fresh) = fresh else {
+                    return self.refresh_diagram_lookup(
+                        "This representation changed. Review the refreshed destinations.",
+                    );
+                };
+                if self.reveal_diagram_usage(&fresh) {
+                    self.diagram_usages = None;
+                    self.status = format!(
+                        "{} · {} in {}",
+                        self.project().named(subject),
+                        fresh.role,
+                        self.project().named(fresh.surface.id())
+                    );
+                    return Task::batch(["model-explorer", "model-browser", "inspector"].map(
+                        |id| {
+                            iced::widget::operation::snap_to(
+                                id,
+                                iced::widget::scrollable::RelativeOffset::START,
+                            )
+                        },
+                    ));
+                }
+            }
+            Event::Open(_) | Event::Close(_) => unreachable!(),
+        }
+        Task::none()
+    }
+
+    /// Explicit saved-Scenario reveal runs before generic Apply. An absent target
+    /// never selects the owner or another saved arrangement as a fallback.
+    pub(super) fn reveal_saved_scenario(&mut self, diagram: Id, selected: Id) -> Task<Message> {
+        if self.diagram_usages.is_some() || !self.usage_navigation_available() {
+            self.status = "Apply or revert pending edits before revealing a saved Scenario. Your inputs are retained.".into();
+            return Task::none();
+        }
+        if presentation::checked_owner(self.project(), Representation::Saved { diagram }).is_none()
+        {
+            return Task::none();
+        }
+        let Some(found) = self
+            .current_surface_usages(selected, Surface::Saved(diagram))
+            .into_iter()
+            .find(|row| matches!(row.target, Target::Whole | Target::ScenarioObject(_)))
+        else {
+            self.status = "This object has no visible target in that saved Scenario.".into();
+            return Task::none();
+        };
+        self.reveal_diagram_usage(&found);
+        Task::none()
+    }
+
+    pub(super) fn reveal_diagram_usage(&mut self, usage: &Usage) -> bool {
+        if !self.usage_navigation_available() {
+            return false;
+        }
+        let previous_layer = self.layer;
+        let scenario_representation = match usage.surface {
+            Surface::Saved(diagram) if self.saved_scenario_diagram(diagram) => {
+                Some(Representation::Saved { diagram })
+            }
+            Surface::Scenario(owner) => Some(Representation::Derived { owner }),
+            _ => None,
+        };
+        if let Some(representation) = scenario_representation {
+            let Some(owner) = presentation::checked_owner(self.project(), representation) else {
+                return false;
+            };
+            if !self
+                .behavior
+                .scenario
+                .representation_usages(self.project(), representation, usage.subject)
+                .iter()
+                .any(|row| row == usage)
+            {
+                return false;
+            }
+            // Finish target/camera admission before changing the App route. The
+            // checked immutable owner also makes the following entry infallible.
+            let revealed = match representation {
+                Representation::Derived { .. } => self.behavior.scenario.reveal_usage(
+                    self.document.project(),
+                    self.canvas_document,
+                    owner,
+                    &usage.target,
+                ),
+                Representation::Saved { .. } => self.behavior.scenario.reveal_representation_usage(
+                    self.document.project(),
+                    self.canvas_document,
+                    owner,
+                    representation,
+                    &usage.target,
+                ),
+            };
+            if !revealed {
+                return false;
+            }
+            if !self.enter_scenario_representation(representation) {
+                return false;
+            }
+        }
+        let p = self.document.project();
+        let (selected, placement) = match &usage.target {
+            Target::Whole => (usage.surface.id(), None),
+            Target::Placement(id) => {
+                let Some(node) = p
+                    .diagrams
+                    .get(&usage.surface.id())
+                    .and_then(|d| d.nodes.get(id))
+                else {
+                    return false;
+                };
+                (node.element, Some(*id))
+            }
+            Target::Port { port, placement } => (*port, Some(*placement)),
+            Target::StateRow {
+                placement,
+                relation,
+            } => (*relation, Some(*placement)),
+            Target::Edge(id)
+            | Target::ProcessLink(id)
+            | Target::ScenarioObject(id)
+            | Target::AllocationGrouping { relation: id, .. }
+            | Target::ProcessPreviewLink { relation: id, .. } => (*id, None),
+            Target::ProcessOccurrence(endpoint) => (
+                endpoint
+                    .references
+                    .first()
+                    .copied()
+                    .unwrap_or(endpoint.occurrence),
+                None,
+            ),
+        };
+        match usage.surface {
+            Surface::Saved(id) => {
+                let Some(diagram) = p.diagrams.get(&id) else {
+                    return false;
+                };
+                self.layer = diagram.layer;
+                self.active_diagram = Some(id);
+                if let Some(owner) = diagram.projection.scenario() {
+                    self.behavior.active_owner = Some(owner);
+                    self.page = Page::Behavior;
+                } else if let Some(machine) = diagram.projection.state_machine() {
+                    let viewport = self.behavior.diagram.viewport.unwrap_or(iced::Size::new(
+                        (self.window_size.width - 610.).max(280.),
+                        (self.window_size.height - 320.).max(240.),
+                    ));
+                    let (zoom, pan) = usage::camera_for(&usage.target, usage.bounds, viewport);
+                    self.behavior.diagram = behavior::state_view::State {
+                        diagram: Some(id),
+                        placement,
+                        viewport: Some(viewport),
+                        zoom,
+                        pan,
+                        fit: false,
+                        ..Default::default()
+                    };
+                    self.behavior.active_owner = Some(machine);
+                    self.page = Page::Behavior;
+                } else {
+                    let viewport = self.canvas_size.unwrap_or(iced::Size::new(
+                        (self.window_size.width - 550.).max(280.),
+                        (self.window_size.height - 284.).max(240.),
+                    ));
+                    (self.zoom, self.pan) =
+                        usage::camera_for(&usage.target, usage.bounds, viewport);
+                    self.fit_to_view = false;
+                    self.page = Page::Diagram;
+                }
+            }
+            Surface::Process(owner) => {
+                if !self.behavior.topology.reveal_usage(
+                    p,
+                    self.canvas_document,
+                    owner,
+                    &usage.target,
+                ) {
+                    return false;
+                }
+                self.layer = p.elements[&owner].layer();
+                self.behavior.active_owner = Some(owner);
+                self.page = Page::Behavior;
+            }
+            Surface::Scenario(owner) => {
+                self.layer = p.elements[&owner].layer();
+                self.behavior.active_owner = Some(owner);
+                self.page = Page::Behavior;
+            }
+        }
+        if scenario_representation.is_none() {
+            self.behavior.scenario.forget_view();
+        }
+        self.selected = selected;
+        self.selected_node = placement;
+        self.model_menu = None;
+        self.canvas_epoch = self.canvas_epoch.wrapping_add(1);
+        self.selected_bend = None;
+        self.connection = None;
+        self.last_workspace_page = self.page;
+        if previous_layer != self.layer {
+            self.data_state = Default::default();
+            self.explorer_index = crate::explorer::Index::new(self.project(), self.layer);
+            self.explorer_focus = None;
+            self.explorer_group = None;
+            self.explorer_page = 0;
+        }
+        self.normalize_creation();
+        self.reveal_explorer_selection();
+        self.refresh_draft();
+        self.diagram_navigation_focus = Some(usage::Focus {
+            context: Context {
+                document: self.canvas_document,
+                revision: self.document.revision(),
+                subject: usage.subject,
+            },
+            usage: usage.clone(),
+            selected,
+        });
+        self.pending_scenario_reveal_visit = scenario_representation.and_then(|representation| {
+            let owner = presentation::checked_owner(self.project(), representation)?;
+            self.behavior
+                .scenario
+                .context(
+                    self.canvas_document,
+                    owner,
+                    self.document.revision(),
+                    self.canvas_epoch,
+                )
+                .map(|context| context.visit)
+        });
+        self.pending_diagram_reveal = Some((
+            Context {
+                document: self.canvas_document,
+                revision: self.document.revision(),
+                subject: usage.subject,
+            },
+            usage.clone(),
+            self.canvas_epoch,
+        ));
+        true
+    }
+
+    /// Validated presentation identity. Edit selection and Delete capture remain
+    /// semantic; a port owner or allocation work box is only a visual marker.
+    pub(crate) fn diagram_focus(&self, surface: Surface) -> Option<&Usage> {
+        let focus = self.diagram_navigation_focus.as_ref()?;
+        let current_surface = match surface {
+            Surface::Saved(id) => {
+                self.active_diagram == Some(id)
+                    && matches!(self.page, Page::Diagram | Page::Behavior)
+                    && (!self.saved_scenario_diagram(id)
+                        || (self.page == Page::Behavior
+                            && self.behavior.scenario.representation()
+                                == Some(Representation::Saved { diagram: id })))
+            }
+            Surface::Process(owner) => {
+                self.page == Page::Behavior && self.behavior.active_owner == Some(owner)
+            }
+            Surface::Scenario(owner) => {
+                self.page == Page::Behavior
+                    && self.behavior.active_owner == Some(owner)
+                    && self.behavior.scenario.representation()
+                        == Some(Representation::Derived { owner })
+            }
+        };
+        (current_surface
+            && focus.usage.surface == surface
+            && focus.context.document == self.canvas_document
+            && focus.context.revision == self.document.revision()
+            && focus.selected == self.selected)
+            .then_some(&focus.usage)
+    }
+}

crates/oa-desktop/src/app/diagram_usages/tests/saved_scenario.arcadia

@@ -0,0 +1,108 @@
+arcadia 7;
+project incident_workspace "Incident report review" id "70200000-0000-4000-8000-000000000001" {
+    // Two operational activities, with one lifeline appearance per Scenario.
+    oa_activity report_incident "Report incident" id "70200000-0000-4000-8000-000000000002" {}
+    oa_activity assess_incident "Assess incident" id "70200000-0000-4000-8000-000000000003" {}
+    interaction incident_report "Incident report" id "70200000-0000-4000-8000-000000000004" {
+        source @report_incident;
+        target @assess_incident;
+    }
+
+    oa_scenario incident_response "Review a reported incident" id "70200000-0000-4000-8000-000000000010" {
+        viewpoint OperationalActivity;
+        steps [@initial_report, @updated_report, @assess_call, @assess_reply, @unfinished_notice, @use_review];
+    }
+    oa_lifeline reporter "Reporting activity" id "70200000-0000-4000-8000-000000000011" {
+        parent @incident_response; represented @report_incident;
+    }
+    oa_lifeline assessor "Assessment activity" id "70200000-0000-4000-8000-000000000012" {
+        parent @incident_response; represented @assess_incident;
+    }
+    // Both appearances reuse one definition. Navigation must retain the occurrence.
+    oa_occurrence initial_report "Initial incident report" id "70200000-0000-4000-8000-000000000020" {
+        parent @incident_response;
+        body { Exchange { exchange @incident_report; sender @reporter; receiver @assessor; message_kind Asynchronous; }; };
+    }
+    oa_occurrence updated_report "Updated incident report" id "70200000-0000-4000-8000-000000000021" {
+        parent @incident_response;
+        body { Exchange { exchange @incident_report; sender @reporter; receiver @assessor; message_kind Asynchronous; }; };
+    }
+    // A correlated self call/reply with deliberately unassigned exchange definitions.
+    oa_occurrence assess_call "Assess report details" id "70200000-0000-4000-8000-000000000022" {
+        parent @incident_response;
+        body { Exchange { exchange none; sender @assessor; receiver @assessor; message_kind Call; }; };
+    }
+    oa_occurrence assess_reply "Assessment ready" id "70200000-0000-4000-8000-000000000023" {
+        parent @incident_response;
+        body { Exchange { exchange none; sender @assessor; receiver @assessor; message_kind Reply; reply_to @assess_call; }; };
+    }
+    // Intentional unfinished work: no receiver and therefore no fabricated arrow.
+    oa_occurrence unfinished_notice "Follow-up recipient undecided" id "70200000-0000-4000-8000-000000000024" {
+        parent @incident_response;
+        body { Exchange { exchange @incident_report; sender @reporter; receiver none; message_kind Asynchronous; }; };
+    }
+    oa_occurrence use_review "Use the reviewed reporting procedure" id "70200000-0000-4000-8000-000000000025" {
+        parent @incident_response;
+        body { ScenarioUse {
+            bindings [{ local @reporter; referenced @review_reporter; }, { local @assessor; referenced @review_assessor; }];
+            scenario @reporting_review;
+        }; };
+    }
+
+    // This definition stays opaque in the caller. Open it, then Back to the saved view.
+    oa_scenario reporting_review "Reporting procedure detail" id "70200000-0000-4000-8000-000000000030" {
+        viewpoint OperationalActivity;
+        steps [@review_delivery];
+    }
+    oa_lifeline review_reporter "Reporting activity in detail" id "70200000-0000-4000-8000-000000000031" {
+        parent @reporting_review; represented @report_incident;
+    }
+    oa_lifeline review_assessor "Assessment activity in detail" id "70200000-0000-4000-8000-000000000032" {
+        parent @reporting_review; represented @assess_incident;
+    }
+    oa_occurrence review_delivery "Check the incident report" id "70200000-0000-4000-8000-000000000033" {
+        parent @reporting_review;
+        body { Exchange { exchange @incident_report; sender @review_reporter; receiver @review_assessor; message_kind Asynchronous; }; };
+    }
+
+    diagram incident_readable "A - Incident review readable" id "70200000-0000-4000-8000-000000000040" {
+        layer Oa;
+        projection { Scenario { scenario @incident_response; }; };
+        layout { Scenario {
+            lanes [{ lifeline @reporter; x 160; }, { lifeline @assessor; x 640; }];
+            messages [
+                { address { references []; occurrence @initial_report; }; send_y 160; },
+                { address { references []; occurrence @updated_report; }; send_y 252; },
+                { address { references []; occurrence @assess_call; }; send_y 344; },
+                { address { references []; occurrence @assess_reply; }; send_y 436; }
+            ];
+        }; };
+    }
+    diagram incident_wide "B - Incident review negative and far" id "70200000-0000-4000-8000-000000000041" {
+        layer Oa;
+        projection { Scenario { scenario @incident_response; }; };
+        layout { Scenario {
+            lanes [{ lifeline @reporter; x -500; }, { lifeline @assessor; x 50000; }];
+            messages [
+                { address { references []; occurrence @initial_report; }; send_y 160; },
+                { address { references []; occurrence @updated_report; }; send_y 252; },
+                { address { references []; occurrence @assess_call; }; send_y 344; },
+                { address { references []; occurrence @assess_reply; }; send_y 436; }
+            ];
+        }; };
+    }
+    diagram incident_repair "C - Incident review needs layout repair" id "70200000-0000-4000-8000-000000000042" {
+        layer Oa;
+        projection { Scenario { scenario @incident_response; }; };
+        layout { Scenario {
+            // These valid authored lanes must remain saved during complete fallback.
+            lanes [{ lifeline @reporter; x 900; }, { lifeline @assessor; x -500; }];
+            messages [
+                // REPAIR: change only this 300 to 424, then Undo and Redo the edit.
+                { address { references []; occurrence @assess_reply; }; send_y 300; },
+                // This authored value stays latent while the receiver is missing.
+                { address { references []; occurrence @unfinished_notice; }; send_y 2000; }
+            ];
+        }; };
+    }
+}

crates/oa-desktop/src/app/diagram_usages/tests/saved_scenario.rs

@@ -0,0 +1,362 @@
+//! Actual App chooser/explicit-reveal checks for saved Scenario identity and source history.
+use super::*;
+use crate::behavior::scenario::{CanvasEvent, State};
+use crate::behavior::scenario_layout::{
+    Representation,
+    presentation::{self, PresentationStatus},
+};
+use iced::{Size, Vector};
+
+fn fixture() -> App {
+    let p = language::parse(include_str!("saved_scenario.arcadia")).unwrap();
+    let errors: Vec<_> = oa_core::validation::validate(&p)
+        .into_iter()
+        .filter(|d| d.severity == oa_core::validation::Severity::Error)
+        .collect();
+    assert!(errors.is_empty(), "{errors:?}");
+    App::with_project(p)
+}
+fn id(app: &App, alias: &str) -> Id {
+    app.project()
+        .identities()
+        .into_iter()
+        .find(|(_, a)| *a == alias)
+        .unwrap()
+        .0
+}
+fn representation(view: Id) -> Representation {
+    Representation::Saved { diagram: view }
+}
+fn find(app: &App, subject: Id, view: Id) -> Usage {
+    usage::saved_usages_for(app.project(), subject, Some(view))
+        .into_iter()
+        .find(|row| row.target == Target::ScenarioObject(subject))
+        .expect("exact saved occurrence")
+}
+fn context(app: &App) -> behavior::scenario::Context {
+    let owner = app.behavior.active_owner.unwrap();
+    app.behavior
+        .scenario
+        .context(
+            app.canvas_document,
+            owner,
+            app.document.revision(),
+            app.canvas_epoch,
+        )
+        .unwrap()
+}
+fn navigate(app: &mut App, subject: Id, view: Id) -> Id {
+    let (token, rows) = open(app, subject);
+    let found = rows
+        .into_iter()
+        .find(|u| u.surface == Surface::Saved(view) && u.target == Target::ScenarioObject(subject))
+        .expect("saved chooser destination");
+    choose(app, token, found);
+    assert!(app.diagram_usages.is_none());
+    assert_eq!(app.page, Page::Behavior);
+    assert_eq!(app.active_diagram, Some(view));
+    assert_eq!(
+        app.behavior.scenario.representation(),
+        Some(representation(view))
+    );
+    assert_eq!(app.selected, subject);
+    token
+}
+
+#[test]
+fn saved_queries_use_each_actual_presentation_and_keep_repeated_appearances_and_references_opaque()
+{
+    let app = fixture();
+    let owner = id(&app, "incident_response");
+    let first = id(&app, "initial_report");
+    let second = id(&app, "updated_report");
+    let exchange = id(&app, "incident_report");
+    let latent = id(&app, "unfinished_notice");
+    let callee_message = id(&app, "review_delivery");
+    let views = ["incident_readable", "incident_wide", "incident_repair"].map(|a| id(&app, a));
+    let derived = app
+        .behavior
+        .scenario
+        .diagram_usages(app.project(), owner, first)
+        .pop()
+        .unwrap();
+    let rows = views.map(|view| find(&app, first, view));
+    assert_eq!(rows[0].bounds.y - derived.bounds.y, 12.);
+    assert_ne!(rows[0].bounds, rows[1].bounds);
+    assert_eq!(
+        rows[2].bounds, derived.bounds,
+        "complete fallback cannot retain the authored lane override"
+    );
+    for view in views {
+        let represented = usage::saved_usages_for(app.project(), exchange, Some(view));
+        assert_eq!(represented.len(), 2);
+        assert!(
+            represented
+                .iter()
+                .any(|u| u.target == Target::ScenarioObject(first))
+        );
+        assert!(
+            represented
+                .iter()
+                .any(|u| u.target == Target::ScenarioObject(second))
+        );
+        assert!(
+            represented
+                .iter()
+                .all(|u| u.surface == Surface::Saved(view))
+        );
+        assert!(usage::saved_usages_for(app.project(), callee_message, Some(view)).is_empty());
+        assert_eq!(
+            find(&app, latent, view).target,
+            Target::ScenarioObject(latent)
+        );
+        let shown = presentation::present(app.project(), representation(view), owner);
+        let whole = usage::saved_usages_for(app.project(), view, Some(view));
+        assert_eq!(whole.len(), 1);
+        assert_eq!(whole[0].target, Target::Whole);
+        assert_eq!(Some(whole[0].bounds), shown.bounds());
+    }
+    let wide = presentation::present(app.project(), representation(views[1]), owner)
+        .bounds()
+        .unwrap();
+    assert!(wide.x < -500. && wide.x + wide.width > 50000.);
+    let fallback = presentation::present(app.project(), representation(views[2]), owner);
+    assert!(matches!(
+        fallback.status(),
+        PresentationStatus::Fallback { .. }
+    ));
+    assert_eq!(fallback.latent_messages(), &[latent]);
+    assert!(!fallback.capabilities().coordinate_input);
+}
+
+#[test]
+fn saved_chooser_and_explicit_reveal_preserve_complete_source_and_actual_undo_redo() {
+    for alias in ["incident_readable", "incident_wide", "incident_repair"] {
+        let mut app = fixture();
+        let view = id(&app, alias);
+        let first = id(&app, "initial_report");
+        let owner = id(&app, "incident_response");
+        let original = app.document.snapshot();
+        app.document
+            .execute(Command::Rename(first, "Reviewed incident report".into()))
+            .unwrap();
+        let edited = app.document.snapshot();
+        app.sync_source();
+        app.refresh_draft();
+        let before = authored(&app);
+        navigate(&mut app, first, view);
+        assert_eq!(app.behavior.active_owner, Some(owner));
+        assert_eq!(authored(&app), before);
+        send(&mut app, Message::RevealInDiagram(view, first));
+        assert_eq!(app.active_diagram, Some(view));
+        assert_eq!(authored(&app), before);
+        assert!(app.document.undo());
+        assert_eq!(app.project(), &original.decoded.project);
+        assert_eq!(app.document.bundle(), &original.bundle);
+        assert!(app.document.redo());
+        assert_eq!(app.project(), &edited.decoded.project);
+        assert_eq!(app.document.bundle(), &edited.bundle);
+    }
+}
+
+#[test]
+fn saved_reveal_and_chooser_refuse_source_property_and_behavior_drafts() {
+    for chooser in [false, true] {
+        for block in 0..3 {
+            let mut app = fixture();
+            let view = id(&app, "incident_repair");
+            let first = id(&app, "initial_report");
+            let choice = chooser.then(|| {
+                let (token, rows) = open(&mut app, first);
+                (
+                    token,
+                    rows.into_iter()
+                        .find(|u| u.surface == Surface::Saved(view))
+                        .unwrap(),
+                )
+            });
+            match block {
+                0 => {
+                    let cursor = app.source_editor.cursor();
+                    app.source_workspace
+                        .edit("? preserve unfinished source".into(), cursor);
+                }
+                1 => {
+                    app.draft
+                        .as_mut()
+                        .unwrap()
+                        .input("/name", "Unapplied inspector value".into());
+                    assert!(app.draft_dirty());
+                }
+                _ => {
+                    let p = app.project().clone();
+                    app.behavior
+                        .creation
+                        .update(&p, behavior::creation::Event::Open(Layer::Oa))
+                        .unwrap();
+                    assert!(app.behavior.has_pending());
+                }
+            }
+            let before = authored(&app);
+            let prior = location(&app);
+            let draft = app
+                .draft
+                .as_ref()
+                .map(|d| serde_json::to_value(d.recovery_snapshot()).unwrap());
+            if let Some((token, row)) = choice {
+                choose(&mut app, token, row);
+            } else {
+                send(&mut app, Message::RevealInDiagram(view, first));
+            }
+            assert_eq!(authored(&app), before);
+            assert_eq!(location(&app), prior);
+            assert_eq!(
+                app.draft
+                    .as_ref()
+                    .map(|d| serde_json::to_value(d.recovery_snapshot()).unwrap()),
+                draft
+            );
+        }
+    }
+}
+
+#[test]
+fn saved_a_b_a_rejects_old_visit_and_panel_callbacks_before_deferred_measurement() {
+    let mut app = fixture();
+    let a = id(&app, "incident_readable");
+    let b = id(&app, "incident_wide");
+    let first = id(&app, "initial_report");
+    let before = authored(&app);
+    let old_token = navigate(&mut app, first, a);
+    let old = context(&app);
+    navigate(&mut app, first, b);
+    navigate(&mut app, first, a);
+    let current = context(&app);
+    assert_ne!(old.visit, current.visit);
+    let held = behavior::scenario::Context {
+        epoch: current.epoch,
+        ..old
+    };
+    let camera = app.behavior.scenario.camera_boundary();
+    send(
+        &mut app,
+        Message::ScenarioCanvas(CanvasEvent::Viewport(held, Size::new(900., 900.))),
+    );
+    send(
+        &mut app,
+        Message::ScenarioCanvas(CanvasEvent::Shelf(
+            held,
+            crate::behavior::scenario::Shelf::Selection,
+        )),
+    );
+    send(
+        &mut app,
+        Message::DiagramUsage(Event::Search(old_token, "obsolete filter".into())),
+    );
+    send(&mut app, Message::DiagramUsage(Event::Close(old_token)));
+    assert_eq!(app.pending_scenario_reveal_visit, Some(current.visit));
+    assert!(app.pending_diagram_reveal.is_some());
+    assert!(app.behavior.scenario.camera_boundary() == camera);
+    let bounds = find(&app, first, a).bounds;
+    send(
+        &mut app,
+        Message::ScenarioCanvas(CanvasEvent::Viewport(current, Size::new(500., 300.))),
+    );
+    assert!(app.pending_diagram_reveal.is_none());
+    assert_eq!(context(&app).visit, current.visit);
+    let mut expected = State::default();
+    expected.enter_representation(app.canvas_document, current.scenario, representation(a));
+    expected.viewport(Size::new(500., 300.));
+    expected.zoom(Some(1.25));
+    expected.camera(
+        app.project(),
+        current.scenario,
+        behavior::canvas_workspace::Event::Pan(Vector::new(
+            250. - bounds.center_x() * 1.25,
+            150. - bounds.center_y() * 1.25,
+        )),
+    );
+    assert!(app.behavior.scenario.camera_boundary() == expected.camera_boundary());
+    assert_eq!(authored(&app), before);
+}
+
+#[test]
+fn retargeted_saved_view_cannot_reveal_a_former_owner_occurrence() {
+    let mut app = fixture();
+    let first = id(&app, "initial_report");
+    let view = id(&app, "incident_readable");
+    let other = id(&app, "reporting_review");
+    let (token, rows) = open(&mut app, first);
+    let old = rows
+        .into_iter()
+        .find(|u| u.surface == Surface::Saved(view))
+        .unwrap();
+    let mut replacement = app.project().diagrams[&view].clone();
+    replacement.projection = ProjectionKind::Scenario { scenario: other };
+    replacement.layout = None;
+    app.document
+        .execute(Command::EditDiagram(view, replacement))
+        .unwrap();
+    app.sync_source();
+    app.refresh_draft();
+    let before = authored(&app);
+    let prior = location(&app);
+    choose(&mut app, token, old);
+    assert_eq!(location(&app), prior);
+    assert_eq!(authored(&app), before);
+    finish_lookup(&mut app);
+    let token = app.diagram_usages.as_ref().unwrap().token;
+    assert!(
+        app.diagram_usages
+            .as_ref()
+            .unwrap()
+            .usages
+            .iter()
+            .all(|u| u.surface != Surface::Saved(view))
+    );
+    send(&mut app, Message::DiagramUsage(Event::Close(token)));
+    send(&mut app, Message::RevealInDiagram(view, first));
+    assert_eq!(location(&app), prior);
+    assert_eq!(authored(&app), before);
+}
+
+#[test]
+fn explicit_saved_layout_repair_undo_redo_requeries_authored_and_fallback_geometry_without_extra_history()
+ {
+    let mut app = fixture();
+    let view = id(&app, "incident_repair");
+    let first = id(&app, "initial_report");
+    let reply = id(&app, "assess_reply");
+    let before = app.document.snapshot();
+    let fallback = find(&app, first, view);
+    app.document
+        .execute(Command::SetScenarioMessagePosition {
+            diagram: view,
+            position: oa_core::ScenarioMessagePosition {
+                address: oa_core::OccurrenceEndpoint {
+                    references: vec![],
+                    occurrence: reply,
+                },
+                send_y: 424.,
+            },
+        })
+        .unwrap();
+    app.sync_source();
+    app.refresh_draft();
+    let repaired = app.document.snapshot();
+    let authored_row = find(&app, first, view);
+    assert_ne!(authored_row.bounds, fallback.bounds);
+    navigate(&mut app, first, view);
+    assert!(app.document.undo());
+    app.sync_source();
+    app.refresh_draft();
+    assert_eq!(app.project(), &before.decoded.project);
+    assert_eq!(app.document.bundle(), &before.bundle);
+    assert_eq!(find(&app, first, view).bounds, fallback.bounds);
+    assert!(app.document.redo());
+    app.sync_source();
+    app.refresh_draft();
+    assert_eq!(app.project(), &repaired.decoded.project);
+    assert_eq!(app.document.bundle(), &repaired.bundle);
+    assert_eq!(find(&app, first, view).bounds, authored_row.bounds);
+}

crates/oa-desktop/src/app/hosted.rs

@@ -213,6 +213,14 @@ impl App {
             self.pending = None;
             return Task::none();
         }
+        if self.path.is_some()
+            || self.hosted.session.as_ref().is_none_or(|session| {
+                session.resource_id != remote.resource_id
+                    || session.connection.base() != request.connection.base()
+            })
+        {
+            self.reset_source_navigation_session();
+        }
         self.hosted.session = Some(Session {
             connection: request.connection.clone(),
             resource_id: remote.resource_id,
@@ -345,6 +353,14 @@ impl App {
                         match self.document.apply_compiled((*remote.compiled).clone()) {
                             Ok(_) => {
                                 self.document.mark_saved(remote.compiled.clone());
+                                if self.path.is_some()
+                                    || self.hosted.session.as_ref().is_none_or(|session| {
+                                        session.resource_id != remote.resource_id
+                                            || session.connection.base() != connection.base()
+                                    })
+                                {
+                                    self.reset_source_navigation_session();
+                                }
                                 self.hosted.session = Some(Session {
                                     connection,
                                     resource_id: remote.resource_id,

crates/oa-desktop/src/app/process_canvas.rs

@@ -15,18 +15,15 @@ impl App {
             epoch: self.canvas_epoch,
         })
     }
-    pub(super) fn reveal_process_selection(&self) -> Task<Message> {
-        let Some(context) = self.topology_context() else {
-            return Task::none();
-        };
-        let Some(offset) =
-            self.behavior
-                .topology
-                .selection_offset(self.project(), context.owner, self.selected)
-        else {
-            return Task::none();
-        };
-        iced::widget::operation::scroll_to("process-canvas", offset)
+    pub(super) fn reveal_process_selection(&mut self) -> Task<Message> {
+        if let Some(context) = self.topology_context() {
+            let mut state = std::mem::take(&mut self.behavior.topology);
+            if state.reveal_selection(self.project(), context.owner, self.selected) {
+                self.canvas_epoch = self.canvas_epoch.wrapping_add(1);
+            }
+            self.behavior.topology = state;
+        }
+        Task::none()
     }
     pub(super) fn edit_process_canvas(&mut self, event: CanvasEvent) -> Task<Message> {
         let context = event.context();
@@ -52,6 +49,44 @@ impl App {
             }
             return Task::none();
         }
+        if let CanvasEvent::Camera(_, lifetime, input) = event {
+            use crate::behavior::canvas_workspace::{self, Event};
+            if lifetime != self.camera_epoch
+                || !self.topology_context().is_some_and(|c| {
+                    c.document == context.document
+                        && c.owner == context.owner
+                        && c.revision == context.revision
+                })
+            {
+                return Task::none();
+            }
+            let scope = canvas_workspace::Scope {
+                document: context.document,
+                owner: context.owner,
+                revision: context.revision,
+                epoch: lifetime,
+                scenario_view: None,
+            };
+            if self.behavior.has_pending()
+                || self.draft_dirty()
+                || self.source_dirty()
+                || !canvas_workspace::keyboard_enabled(self)
+            {
+                return Task::none();
+            }
+            match input {
+                Event::Traverse(_) | Event::ControlFocus(_) | Event::ToggleFocus | Event::Leave => {
+                    return canvas_workspace::focus_task(scope, input);
+                }
+                Event::CancelGesture => self.canvas_epoch = self.canvas_epoch.wrapping_add(1),
+                input => {
+                    if self.behavior.topology.camera(input) {
+                        self.canvas_epoch = self.canvas_epoch.wrapping_add(1);
+                    }
+                }
+            }
+            return Task::none();
+        }
         if self.topology_context() != Some(context) {
             return Task::none();
         }
@@ -59,6 +94,26 @@ impl App {
             .topology
             .enter(context.document, context.owner);
         match event {
+            CanvasEvent::Remove(_, id) => {
+                if diagram_removal::enabled(self)
+                    && self.selected == id
+                    && self.behavior.topology.selecting()
+                {
+                    if self
+                        .behavior
+                        .topology
+                        .has_qualified_selection(self.project(), context.owner)
+                    {
+                        self.status = "Open the referenced definition to delete its contents, or select the outer reference to remove that use.".into();
+                    } else if self.behavior.topology.removal_target(
+                        self.project(),
+                        context.owner,
+                        id,
+                    ) {
+                        self.begin_model_delete(None);
+                    }
+                }
+            }
             CanvasEvent::ExpandQualified(_, endpoint) => {
                 let mut state = std::mem::take(&mut self.behavior.topology);
                 let changed = state.expand_context(self.project(), context.owner, endpoint);
@@ -81,6 +136,7 @@ impl App {
                             .first()
                             .copied()
                             .unwrap_or(endpoint.occurrence),
+                        resolved.defining_sequence,
                     );
                     self.behavior.active_owner = Some(resolved.defining_sequence);
                     self.select(endpoint.occurrence);
@@ -104,10 +160,6 @@ impl App {
                     self.behavior.topology.select_context(resolved.address);
                 }
             }
-            CanvasEvent::Focus(_) => {
-                self.behavior.topology.focused = !self.behavior.topology.focused;
-                self.canvas_epoch = self.canvas_epoch.wrapping_add(1);
-            }
             CanvasEvent::Select(_, id) => {
                 if !self.behavior.has_pending()
                     && crate::behavior::selected_behavior(self.project(), id) == Some(context.owner)
@@ -118,14 +170,18 @@ impl App {
                 }
             }
             CanvasEvent::Choose(_, tool) => {
-                if self.behavior.has_pending() || !self.apply() {
+                if self.behavior.has_pending() || self.draft_dirty() || self.source_dirty() {
+                    self.status =
+                        "Apply or cancel pending edits before choosing a process tool.".into();
                     return Task::none();
                 }
                 self.behavior.topology.choose(tool);
                 self.canvas_epoch = self.canvas_epoch.wrapping_add(1);
             }
             CanvasEvent::Zoom(_, zoom) => {
-                self.behavior.topology.zoom(zoom);
+                let mut state = std::mem::take(&mut self.behavior.topology);
+                state.camera_zoom(self.project(), context.owner, zoom);
+                self.behavior.topology = state;
                 self.canvas_epoch = self.canvas_epoch.wrapping_add(1);
             }
             CanvasEvent::Expand(_, id) => {
@@ -149,7 +205,9 @@ impl App {
                         .get(&target)
                         .is_some_and(|e| matches!(e.kind(), Kind::Process | Kind::FunctionalChain))
                     {
-                        self.behavior.topology.remember(context.owner, occurrence);
+                        self.behavior
+                            .topology
+                            .remember(context.owner, occurrence, target);
                         self.behavior.active_owner = Some(target);
                     }
                     self.canvas_epoch = self.canvas_epoch.wrapping_add(1);
@@ -284,7 +342,7 @@ mod tests {
         }
     }
     #[test]
-    fn process_focus_retains_rejected_draft_and_guards_selection_until_panels_restore() {
+    fn process_zoom_retains_rejected_draft_and_guards_selection() {
         let (mut app, f) = setup();
         let original = app.document.snapshot();
         let initial = app.selected;
@@ -294,9 +352,14 @@ mod tests {
             &mut app,
             Event::Name("  unfinished contextual work  ".into()),
         );
+        let camera = app.behavior.topology.camera_boundary();
         let context = app.topology_context().unwrap();
-        let _ = app.update(Message::TopologyCanvas(CanvasEvent::Focus(context)));
-        assert!(app.behavior.topology.focused);
+        let _ = app.update(Message::TopologyCanvas(CanvasEvent::Zoom(
+            context,
+            Some(0.75),
+        )));
+        assert_ne!(app.canvas_epoch, context.epoch);
+        assert!(app.behavior.topology.camera_boundary() != camera);
         let raw = app.behavior.recovery_snapshot().unwrap();
         let context = app.topology_context().unwrap();
         let _ = app.update(Message::TopologyCanvas(CanvasEvent::Select(
@@ -308,8 +371,8 @@ mod tests {
         assert_eq!(app.behavior.recovery_snapshot().unwrap(), raw);
         assert!(Arc::ptr_eq(&original, &app.document.snapshot()));
         let context = app.topology_context().unwrap();
-        let _ = app.update(Message::TopologyCanvas(CanvasEvent::Focus(context)));
-        assert!(!app.behavior.topology.focused);
+        let _ = app.update(Message::TopologyCanvas(CanvasEvent::Zoom(context, None)));
+        assert_ne!(app.canvas_epoch, context.epoch);
         assert_eq!(app.behavior.recovery_snapshot().unwrap(), raw);
     }
     #[test]
@@ -524,32 +587,30 @@ mod tests {
         assert!(!app.behavior.has_pending());
     }
     #[test]
-    fn direct_process_app_save_scroll_resize_and_passive_geometry_keep_drafts_and_current_origin() {
+    fn direct_process_app_save_details_resize_and_passive_geometry_keep_drafts_and_camera() {
         let (mut app, f) = setup();
         let context = app.topology_context().unwrap();
+        let _ = app.update(Message::TopologyCanvas(CanvasEvent::Camera(
+            context,
+            app.camera_epoch,
+            behavior::canvas_workspace::Event::Pan(iced::Vector::new(25., 100.)),
+        )));
+        let context = app.topology_context().unwrap();
         let original = app.document.snapshot();
         app.busy = true;
-        for (area, offset) in [
-            (
-                behavior::scenario::ScrollArea::Canvas,
-                iced::Vector::new(25., 100.),
-            ),
-            (
-                behavior::scenario::ScrollArea::Page,
-                iced::Vector::new(0., 40.),
-            ),
-        ] {
-            let _ = app.update(Message::TopologyCanvas(CanvasEvent::Scrolled(
-                context, area, offset,
-            )));
-        }
+        let _ = app.update(Message::TopologyCanvas(CanvasEvent::Scrolled(
+            context,
+            behavior::scenario::ScrollArea::Page,
+            iced::Vector::new(0., 40.),
+        )));
         let _ = app.update(Message::TopologyCanvas(CanvasEvent::Viewport(
             context,
             iced::Size::new(500., 300.),
         )));
+        let camera = app.behavior.topology.camera_boundary();
         assert_eq!(
-            app.behavior.topology.scroll_offset(),
-            iced::Vector::new(25., 140.)
+            app.behavior.topology.details_offset(),
+            iced::Vector::new(0., 40.)
         );
         assert_ne!(app.topology_context(), Some(context));
         assert!(app.busy);
@@ -557,12 +618,12 @@ mod tests {
         stale.document = Id::new_v4();
         let _ = app.update(Message::TopologyCanvas(CanvasEvent::Scrolled(
             stale,
-            behavior::scenario::ScrollArea::Canvas,
+            behavior::scenario::ScrollArea::Page,
             iced::Vector::new(0., 900.),
         )));
         assert_eq!(
-            app.behavior.topology.scroll_offset(),
-            iced::Vector::new(25., 140.)
+            app.behavior.topology.details_offset(),
+            iced::Vector::new(0., 40.)
         );
         let root = PathBuf::from("process-scroll-save-fixture");
         let receipt = FileSnapshot {
@@ -582,6 +643,7 @@ mod tests {
         assert!(!app.busy);
         assert!(!app.document.can_undo());
         assert_eq!(app.project(), &f.p);
+        assert!(app.behavior.topology.camera_boundary() == camera);
         let context = app.topology_context().unwrap();
         let size = app.window_size;
         let _ = app.update(Message::WindowResized(size));

crates/oa-desktop/src/app/reference_authoring.rs

@@ -0,0 +1,304 @@
+//! One transient chooser for the currently mounted Inspector or review field.
+//! Browsing never calls a draft setter or semantic planner.
+use super::{App, Message, Page, Pending};
+use crate::{
+    forms::{
+        Draft,
+        reference_chooser::{self as chooser, Action, Close, Outcome, adapter, trigger},
+    },
+    navigation::InspectorTab,
+    semantic_review::{self, RowAddress, RowEvent},
+    workflow,
+};
+use iced::{Element, Rectangle, Task};
+use oa_core::{FacetSelector, Id, Layer};
+
+#[derive(Debug, Clone, PartialEq, Eq)]
+enum Host {
+    Inspector,
+    Review {
+        address: Option<RowAddress>,
+        facet: FacetSelector,
+    },
+}
+impl Host {
+    fn message(&self, event: chooser::Event) -> Message {
+        match self {
+            Self::Inspector => Message::FieldReferenceEvent(event),
+            Self::Review { address, facet } => {
+                Message::Workflow(workflow::Event::semantic(semantic_review::Event::Row {
+                    address: *address,
+                    facet: Some(facet.clone()),
+                    event: RowEvent::ReferenceEvent(event),
+                }))
+            }
+        }
+    }
+}
+struct Opened {
+    host: Host,
+    request: adapter::Open,
+    document_session: Id,
+    page: Page,
+    layer: Layer,
+    chooser: chooser::State,
+}
+#[derive(Default)]
+pub(super) struct State {
+    opened: Option<Opened>,
+}
+
+impl App {
+    pub(crate) fn reference_input_active(&self) -> bool {
+        self.reference_authoring.opened.is_some()
+    }
+
+    fn reference_draft(&self, host: &Host, path: &str) -> Option<&Draft> {
+        match host {
+            Host::Inspector
+                if self.workflow.is_none() && self.inspector_tab == InspectorTab::Properties =>
+            {
+                self.draft.as_ref()
+            }
+            Host::Review { address, facet } => match self.workflow.as_ref()? {
+                workflow::Workflow::Semantic(state) => {
+                    state.reference_draft(self.project(), *address, facet, path)
+                }
+                _ => None,
+            },
+            _ => None,
+        }
+    }
+    fn reference_available(&self) -> bool {
+        !self.busy
+            && !self.hosted.visible
+            && self.architecture.is_none()
+            && self.model_menu.is_none()
+            && self.file_prompt.is_none()
+            && !self.delete_pending
+            && self.pending.is_none()
+            && !self.source_dirty()
+            && !self.behavior.has_pending()
+            && !matches!(self.page, Page::Home | Page::Guide | Page::Text)
+    }
+    fn reference_valid(&self, opened: &Opened) -> bool {
+        self.reference_available()
+            && self.canvas_document == opened.document_session
+            && self.page == opened.page
+            && self.layer == opened.layer
+            && self.document.revision() == opened.chooser.stamp().context.revision
+            && self.project().id == opened.request.document
+            && self
+                .reference_draft(&opened.host, &opened.request.path)
+                .is_some_and(|draft| draft.reference_matches(&opened.request))
+    }
+    pub(super) fn reconcile_reference_chooser(&mut self) {
+        if self
+            .reference_authoring
+            .opened
+            .as_ref()
+            .is_some_and(|opened| !self.reference_valid(opened))
+        {
+            self.reference_authoring
+                .opened
+                .as_mut()
+                .unwrap()
+                .chooser
+                .invalidate();
+            self.reference_authoring.opened = None;
+        }
+    }
+    fn open_reference(&mut self, host: Host, request: adapter::Open) -> Task<Message> {
+        if !self.reference_available() {
+            return Task::none();
+        }
+        let Some(draft) = self.reference_draft(&host, &request.path) else {
+            return Task::none();
+        };
+        let Ok(chooser) =
+            draft.reference_catalog(self.project(), &request, self.document.revision())
+        else {
+            return Task::none();
+        };
+        self.reference_authoring.opened = Some(Opened {
+            host,
+            request,
+            document_session: self.canvas_document,
+            page: self.page,
+            layer: self.layer,
+            chooser,
+        });
+        Task::none()
+    }
+    fn reference_event(&mut self, host: Host, event: chooser::Event) -> Task<Message> {
+        let Some(mut opened) = self.reference_authoring.opened.take() else {
+            return Task::none();
+        };
+        if !self.reference_valid(&opened) {
+            return Task::none();
+        }
+        if opened.host != host {
+            self.reference_authoring.opened = Some(opened);
+            return Task::none();
+        }
+        match opened.chooser.update(event) {
+            Outcome::Ignored | Outcome::Browsed => {
+                self.reference_authoring.opened = Some(opened);
+                Task::none()
+            }
+            Outcome::Closed(reason) => self.reference_focus(
+                &opened,
+                match reason {
+                    Close::Escape => Some(0),
+                    Close::Tab { backwards } => Some(if backwards { -1 } else { 1 }),
+                    Close::Outside | Close::WindowChanged => None,
+                },
+            ),
+            Outcome::Write { context, value } => {
+                let intent = adapter::Set {
+                    context,
+                    generation: opened.request.generation,
+                    value,
+                };
+                let result = match &opened.host {
+                    Host::Inspector => self
+                        .draft
+                        .as_mut()
+                        .ok_or_else(|| "The property editor closed.".to_owned())
+                        .and_then(|draft| draft.reference_set(self.document.project(), &intent)),
+                    Host::Review { address, facet } => match self.workflow.as_mut() {
+                        Some(workflow::Workflow::Semantic(state)) => {
+                            state.set_reference(self.document.project(), *address, facet, intent)
+                        }
+                        _ => Err("The review editor closed.".into()),
+                    },
+                };
+                if let Err(error) = result {
+                    self.status = error;
+                }
+                // A scoped write rotates field generation. The task targets the
+                // newly rendered field, while a later structural edit makes it inert.
+                self.reference_focus(&opened, Some(0))
+            }
+        }
+    }
+    fn reference_focus(&self, opened: &Opened, step: Option<i32>) -> Task<Message> {
+        let Some(step) = step else {
+            return Task::none();
+        };
+        let Some(draft) = self.reference_draft(&opened.host, &opened.request.path) else {
+            return Task::none();
+        };
+        if draft.reference_session() != opened.request.session {
+            return Task::none();
+        }
+        trigger::focus(
+            draft.reference_session(),
+            draft.reference_generation(),
+            &opened.request.path,
+            step,
+        )
+    }
+    /// Called before generic modal dispatch: the review owns a modal, and this
+    /// chooser owns only its active field. All browser events stop here.
+    pub(super) fn reference_message(&mut self, message: &Message) -> Option<Task<Message>> {
+        self.reconcile_reference_chooser();
+        match message {
+            Message::FieldReferenceOpen(request) => {
+                Some(self.open_reference(Host::Inspector, request.clone()))
+            }
+            Message::FieldReferenceEvent(event) => {
+                Some(self.reference_event(Host::Inspector, event.clone()))
+            }
+            Message::Workflow(workflow::Event::Semantic(review_event)) => {
+                let semantic_review::Event::Row {
+                    address,
+                    facet: Some(facet),
+                    event,
+                } = review_event.as_ref()
+                else {
+                    return None;
+                };
+                let host = Host::Review {
+                    address: *address,
+                    facet: facet.clone(),
+                };
+                match event {
+                    RowEvent::ReferenceOpen(request) => {
+                        Some(self.open_reference(host, request.clone()))
+                    }
+                    RowEvent::ReferenceEvent(event) => {
+                        Some(self.reference_event(host, event.clone()))
+                    }
+                    _ => None,
+                }
+            }
+            Message::Escape | Message::Request(Pending::Close(_))
+                if self.reference_authoring.opened.is_some() =>
+            {
+                let opened = self.reference_authoring.opened.as_ref().unwrap();
+                let host = opened.host.clone();
+                let event = opened.chooser.event(Action::Close(Close::Escape));
+                Some(self.reference_event(host, event))
+            }
+            // Global shortcuts are also emitted for keys captured by the search
+            // input. They must not apply drafts, navigate, or undo the model.
+            Message::Save(_)
+            | Message::ShortcutUndo(_)
+            | Message::Request(Pending::Open | Pending::New)
+            | Message::SourceNavigation(_)
+            | Message::Page(Page::Guide)
+                if self.reference_authoring.opened.is_some() =>
+            {
+                Some(Task::none())
+            }
+            _ => None,
+        }
+    }
+    pub(super) fn reference_overlay<
+        'a,
+        R: iced::advanced::text::Renderer<Font = iced::Font> + 'a,
+    >(
+        &'a self,
+        content: Element<'a, Message, iced::Theme, R>,
+    ) -> Element<'a, Message, iced::Theme, R> {
+        let opened = self
+            .reference_authoring
+            .opened
+            .as_ref()
+            .filter(|opened| self.reference_valid(opened));
+        let host = opened
+            .map(|opened| opened.host.clone())
+            .unwrap_or(Host::Inspector);
+        let focus_scope = if self.reference_available() {
+            match self.workflow.as_ref() {
+                None if self.inspector_tab == InspectorTab::Properties => {
+                    self.draft.as_ref().map(|draft| trigger::FormScope {
+                        session: draft.reference_session(),
+                        modal: false,
+                    })
+                }
+                Some(workflow::Workflow::Semantic(state)) => state
+                    .reference_form(self.project())
+                    .map(|draft| trigger::FormScope {
+                        session: draft.reference_session(),
+                        modal: true,
+                    }),
+                _ => None,
+            }
+        } else {
+            None
+        };
+        chooser::widget::Popup::new(
+            content,
+            opened.map(|opened| &opened.chooser),
+            opened.map_or(Rectangle::default(), |opened| opened.request.anchor),
+            move |event| host.message(event),
+        )
+        .focus_scope(focus_scope)
+        .into()
+    }
+}
+
+#[cfg(test)]
+mod tests;

crates/oa-desktop/src/app/reference_authoring/tests.rs

@@ -0,0 +1,586 @@
+use super::*;
+use crate::forms::Draft;
+use oa_core::*;
+use serde_json::{Value, json};
+
+const OWNER: Id = Id::from_u128(100);
+const BASE: u128 = 10_000;
+const PATH: &str = "/body/Oa/Shared/DataType/definition/Record/supertype";
+
+fn element(p: &mut Project, id: Id, kind: Kind, layer: Layer, name: &str, parent: Option<Id>) {
+    let generated = p.add_element(kind, layer, name, parent).unwrap();
+    let mut element = p.elements.remove(&generated).unwrap();
+    element.id = id;
+    element.alias = format!("object_{}", id.as_u128());
+    if let Some(SharedBody::DataType { definition, .. }) = element.shared_mut() {
+        *definition = DataTypeDefinition::Record { supertype: None };
+    }
+    p.elements.insert(id, element);
+}
+fn catalog() -> Project {
+    let mut p = Project::empty();
+    p.id = Id::from_u128(1);
+    p.name = "Reference catalog".into();
+    element(
+        &mut p,
+        OWNER,
+        Kind::DataType,
+        Layer::Oa,
+        "Edited record",
+        None,
+    );
+    for n in (0..1_000).rev() {
+        let id = Id::from_u128(BASE + n);
+        element(&mut p, id, Kind::DataType, Layer::Oa, "Controller", None);
+        p.elements.get_mut(&id).unwrap().alias = format!("controller_{n:04}");
+    }
+    element(
+        &mut p,
+        Id::from_u128(200),
+        Kind::DataType,
+        Layer::Sa,
+        "Controller",
+        None,
+    );
+    element(
+        &mut p,
+        Id::from_u128(201),
+        Kind::Activity,
+        Layer::Oa,
+        "Controller",
+        None,
+    );
+    p
+}
+fn inspector(p: Project, selected: Id) -> App {
+    let mut app = App::with_project(p);
+    let _ = app.update(Message::Select(selected));
+    app
+}
+fn request(app: &App, host: &Host, path: &str) -> adapter::Open {
+    app.reference_draft(host, path).unwrap().reference_open(
+        app.project(),
+        path,
+        Rectangle {
+            x: 790.,
+            y: 640.,
+            width: 278.,
+            height: 32.,
+        },
+    )
+}
+fn open(app: &mut App, host: &Host, path: &str) {
+    let request = request(app, host, path);
+    let message = match host {
+        Host::Inspector => Message::FieldReferenceOpen(request),
+        Host::Review { address, facet } => {
+            Message::Workflow(workflow::Event::semantic(semantic_review::Event::Row {
+                address: *address,
+                facet: Some(facet.clone()),
+                event: RowEvent::ReferenceOpen(request),
+            }))
+        }
+    };
+    let _ = app.update(message);
+    assert!(
+        app.reference_authoring.opened.is_some(),
+        "field must open: {}",
+        app.status
+    );
+}
+fn event(app: &App, action: Action) -> Message {
+    let opened = app.reference_authoring.opened.as_ref().unwrap();
+    opened.host.message(opened.chooser.event(action))
+}
+fn search(app: &mut App, query: &str) {
+    let serial = app
+        .reference_authoring
+        .opened
+        .as_ref()
+        .unwrap()
+        .chooser
+        .query_serial()
+        + 1;
+    let event = event(
+        app,
+        Action::Query {
+            text: query.into(),
+            serial,
+        },
+    );
+    let _ = app.update(event);
+}
+fn choose(app: &mut App, id: Id) {
+    let event = event(app, Action::Choose(id));
+    let _ = app.update(event);
+}
+fn raw(app: &App) -> Value {
+    serde_json::to_value(app.draft.as_ref().unwrap().recovery_snapshot()).unwrap()
+}
+fn review(app: &App) -> &semantic_review::State {
+    let Some(workflow::Workflow::Semantic(state)) = app.workflow.as_ref() else {
+        panic!("Review is open")
+    };
+    state
+}
+fn send_review(app: &mut App, event: RowEvent) {
+    let addressed = review(app).address_event(event);
+    let _ = app.update(Message::Workflow(workflow::Event::semantic(addressed)));
+}
+fn review_host(app: &App) -> Host {
+    let semantic_review::Event::Row {
+        address,
+        facet: Some(facet),
+        ..
+    } = review(app).address_event(RowEvent::Preview)
+    else {
+        panic!("Active facet")
+    };
+    Host::Review { address, facet }
+}
+fn trace(p: &mut Project, id: Id, oa: Id, sa: Id) {
+    p.traces.insert(
+        id,
+        Trace {
+            id,
+            alias: format!("trace_{}", id.as_u128()),
+            name: "Rationale".into(),
+            description: String::new(),
+            oa,
+            sa,
+            kind: TraceKind::Manual,
+            baseline: None,
+        },
+    );
+}
+
+#[test]
+fn inspector_reference_browse_is_read_only_then_one_scoped_value_applies_with_exact_undo_redo() {
+    let p = catalog();
+    let mut app = inspector(p.clone(), OWNER);
+    let before = app.document.bundle().clone();
+    let revision = app.document.revision();
+    // Malformed escaped text is unrelated to the selected reference. Browsing
+    // and the scoped write must keep its exact spelling and inactive payload.
+    app.draft.as_mut().unwrap().set_exact(true).unwrap();
+    let _ = app.update(Message::Field("/name".into(), "\"unfinished".into()));
+    let raw_before = raw(&app);
+    open(&mut app, &Host::Inspector, PATH);
+    assert_eq!(
+        app.reference_authoring
+            .opened
+            .as_ref()
+            .unwrap()
+            .chooser
+            .count(),
+        1_000
+    );
+    search(&mut app, "controller @controller_0720 OA");
+    let picker = &app.reference_authoring.opened.as_ref().unwrap().chooser;
+    assert_eq!(picker.count(), 1);
+    assert_eq!(picker.highlighted().unwrap().id, Id::from_u128(BASE + 720));
+    assert_eq!(raw(&app), raw_before);
+    assert_eq!(app.document.bundle(), &before);
+    assert_eq!(app.document.revision(), revision);
+    assert!(!app.document.can_undo());
+    // Captured search shortcuts cannot accidentally save/apply or undo a model.
+    let _ = app.update(Message::Save(false));
+    let _ = app.update(Message::ShortcutUndo(false));
+    assert_eq!(raw(&app), raw_before);
+    assert_eq!(app.document.bundle(), &before);
+    choose(&mut app, Id::from_u128(BASE + 720));
+    let mut expected_raw = raw_before;
+    *expected_raw["value"].pointer_mut(PATH).unwrap() = json!(Id::from_u128(BASE + 720));
+    expected_raw["inputs"][PATH] = json!(Id::from_u128(BASE + 720).to_string());
+    assert_eq!(raw(&app), expected_raw);
+    assert_eq!(app.document.bundle(), &before);
+    assert!(!app.document.can_undo());
+    let _ = app.update(Message::Apply);
+    assert_eq!(
+        app.document.bundle(),
+        &before,
+        "Unrelated invalid text remains an Apply error"
+    );
+    let _ = app.update(Message::Field("/name".into(), "\"Edited record\"".into()));
+    let _ = app.update(Message::Apply);
+    let mut expected = p;
+    if let Some(SharedBody::DataType { definition, .. }) =
+        expected.elements.get_mut(&OWNER).unwrap().shared_mut()
+    {
+        *definition = DataTypeDefinition::Record {
+            supertype: Some(Id::from_u128(BASE + 720)),
+        };
+    }
+    assert_eq!(app.project(), &expected);
+    let accepted = app.document.bundle().clone();
+    assert_ne!(accepted, before);
+    let _ = app.update(Message::Undo);
+    assert_eq!(app.document.bundle(), &before);
+    let _ = app.update(Message::Redo);
+    assert_eq!(app.document.bundle(), &accepted);
+    assert_eq!(app.project(), &expected);
+}
+
+#[test]
+fn inspector_reference_retains_invalid_missing_and_incompatible_current_until_explicit_clear() {
+    for (raw_id, expected) in [
+        ("-".into(), "invalid"),
+        (Id::from_u128(999).to_string(), "missing"),
+        (Id::from_u128(200).to_string(), "incompatible"),
+    ] {
+        let mut app = inspector(catalog(), OWNER);
+        app.draft
+            .as_mut()
+            .unwrap()
+            .shape_scoped(PATH, json!(raw_id))
+            .unwrap();
+        let original = raw(&app);
+        let accepted = app.document.bundle().clone();
+        open(&mut app, &Host::Inspector, PATH);
+        let current = &app
+            .reference_authoring
+            .opened
+            .as_ref()
+            .unwrap()
+            .chooser
+            .current;
+        assert!(matches!(
+            (expected, current),
+            ("invalid", chooser::Current::InvalidRaw(_))
+                | ("missing", chooser::Current::Missing(_))
+                | ("incompatible", chooser::Current::Incompatible(_))
+        ));
+        let _ = app.update(Message::Escape);
+        assert_eq!(raw(&app), original);
+        open(&mut app, &Host::Inspector, PATH);
+        let clear = event(&app, Action::Clear);
+        let _ = app.update(clear);
+        assert!(
+            app.draft
+                .as_ref()
+                .unwrap()
+                .value
+                .pointer(PATH)
+                .unwrap()
+                .is_null()
+        );
+        assert_eq!(app.document.bundle(), &accepted);
+        assert!(!app.document.can_undo());
+    }
+}
+
+#[test]
+fn chooser_rejects_old_results_after_context_recovery_reload_or_modal_and_keeps_history_text_out() {
+    for change in 0..7 {
+        let mut app = inspector(catalog(), OWNER);
+        open(&mut app, &Host::Inspector, PATH);
+        let delayed = event(&app, Action::Choose(Id::from_u128(BASE + 1)));
+        match change {
+            0 => {
+                app.draft
+                    .as_mut()
+                    .unwrap()
+                    .shape_scoped(PATH, json!(Id::from_u128(BASE + 2)))
+                    .unwrap();
+            }
+            1 => {
+                let saved = app.draft.as_ref().unwrap().recovery_snapshot();
+                app.draft = Some(Draft::from_recovery(app.project(), saved).unwrap());
+            }
+            2 => {
+                app.canvas_document = Id::new_v4();
+            }
+            3 => {
+                app.hosted.visible = true;
+            }
+            4 => {
+                app.draft
+                    .as_mut()
+                    .unwrap()
+                    .set_context(Some(json!({"different":"scope"})));
+            }
+            5 => {
+                let _ = app.update(Message::Command(Command::Rename(
+                    Id::from_u128(BASE + 3),
+                    "Changed model".into(),
+                )));
+            }
+            _ => {
+                app.source_workspace.edit(
+                    "unfinished source".into(),
+                    iced::widget::text_editor::Cursor {
+                        position: iced::widget::text_editor::Position { line: 0, column: 0 },
+                        selection: None,
+                    },
+                );
+            }
+        }
+        let expected = raw(&app);
+        let source = app.document.bundle().clone();
+        let _ = app.update(delayed);
+        assert!(app.reference_authoring.opened.is_none());
+        assert_eq!(raw(&app), expected);
+        assert_eq!(app.document.bundle(), &source);
+    }
+    let mut p = catalog();
+    trace(&mut p, Id::from_u128(300), OWNER, Id::from_u128(200));
+    let app = inspector(p, Id::from_u128(300));
+    let draft = app.draft.as_ref().unwrap();
+    let request = draft.reference_open(
+        app.project(),
+        "/baseline/semantic/facets/0/references/0/target",
+        Rectangle::default(),
+    );
+    assert!(draft.reference_catalog(app.project(), &request, 0).is_err());
+}
+
+#[test]
+fn reference_array_row_reorder_and_constructor_switch_invalidate_exact_old_field() {
+    let mut p = Project::empty();
+    for n in 0..3 {
+        element(
+            &mut p,
+            Id::from_u128(BASE + n),
+            Kind::ExchangeItem,
+            Layer::Oa,
+            "Signal item",
+            None,
+        );
+    }
+    element(&mut p, OWNER, Kind::Event, Layer::Oa, "Signal", None);
+    *p.elements.get_mut(&OWNER).unwrap().shared_mut().unwrap() = SharedBody::Event {
+        body: EventBody::Signal {
+            items: vec![Id::from_u128(BASE), Id::from_u128(BASE + 1)],
+        },
+    };
+    let mut app = inspector(p, OWNER);
+    let list = "/body/Oa/Shared/Event/body/Signal/items";
+    let path = format!("{list}/0");
+    open(&mut app, &Host::Inspector, &path);
+    let delayed = event(&app, Action::Choose(Id::from_u128(BASE + 2)));
+    let _ = app.update(Message::FieldArray(list.into(), Some(0), 1));
+    let expected = raw(&app);
+    assert_eq!(
+        app.draft.as_ref().unwrap().value.pointer(list),
+        Some(&json!([Id::from_u128(BASE + 1), Id::from_u128(BASE)]))
+    );
+    let _ = app.update(delayed);
+    assert_eq!(raw(&app), expected);
+    open(&mut app, &Host::Inspector, &path);
+    let delayed = event(&app, Action::Choose(Id::from_u128(BASE + 2)));
+    let _ = app.update(Message::FieldVariant(
+        "/body/Oa/Shared/Event/body".into(),
+        json!({"Change":{"expression":"unfinished"}}),
+    ));
+    let expected = raw(&app);
+    let _ = app.update(delayed);
+    assert_eq!(raw(&app), expected);
+    assert!(!app.document.can_undo());
+}
+
+#[test]
+fn review_reference_facets_groups_and_attachment_hosts_browse_without_replanning_and_reject_old_facet()
+ {
+    for mode in 0..3 {
+        let mut p = Project::empty();
+        p.id = Id::from_u128(1);
+        for (id, layer, parent) in [
+            (100, Layer::Oa, None),
+            (101, Layer::Sa, None),
+            (102, Layer::Sa, None),
+            (103, Layer::Oa, Some(Id::from_u128(100))),
+            (104, Layer::Sa, Some(Id::from_u128(101))),
+        ] {
+            element(
+                &mut p,
+                Id::from_u128(id),
+                if parent.is_some() {
+                    Kind::DataField
+                } else {
+                    Kind::DataType
+                },
+                layer,
+                "Record",
+                parent,
+            );
+        }
+        trace(
+            &mut p,
+            Id::from_u128(300),
+            Id::from_u128(100),
+            Id::from_u128(101),
+        );
+        let facet = match mode {
+            0 => FacetSelector::Data(DataFacet::RecordSupertype),
+            1 => FacetSelector::Data(DataFacet::Constructor),
+            _ => FacetSelector::Child(KeyPair {
+                oa: Some(Id::from_u128(103)),
+                sa: Some(Id::from_u128(104)),
+            }),
+        };
+        let path = if mode == 2 {
+            "/parent"
+        } else {
+            "/body/Sa/Shared/DataType/definition/Record/supertype"
+        };
+        let mut app = App::with_project(p.clone());
+        let _ = app.update(Message::StartSemanticReview(Id::from_u128(100)));
+        if mode == 2 {
+            // A paired attachment is a real catalog facet only after explicit
+            // correspondence; selecting an unstaged synthetic pair is rejected.
+            for (id, oa) in [(103, true), (104, false)] {
+                let choice = crate::app::Choice {
+                    id: Id::from_u128(id),
+                    label: format!("Record · @object_{id}"),
+                };
+                send_review(
+                    &mut app,
+                    if oa {
+                        RowEvent::ReferenceOa(choice)
+                    } else {
+                        RowEvent::ReferenceSa(choice)
+                    },
+                );
+            }
+            send_review(&mut app, RowEvent::AddReference);
+        }
+        send_review(&mut app, RowEvent::Select(facet.clone()));
+        send_review(
+            &mut app,
+            RowEvent::Decide(facet.clone(), Some(SemanticDecision::Candidate)),
+        );
+        let host = review_host(&app);
+        let record = if mode == 2 {
+            Id::from_u128(104)
+        } else {
+            Id::from_u128(101)
+        };
+        assert_eq!(
+            app.reference_draft(&host, path)
+                .unwrap_or_else(|| {
+                    panic!(
+                        "Reference fixture mode={mode}, facet={facet:?}, selected={:?}, decisions={:?}, error={:?}",
+                        review(&app).selected,
+                        review(&app).decisions,
+                        review(&app).error
+                    )
+                })
+                .original,
+            record
+        );
+        let before = review(&app).recovery_snapshot().unwrap();
+        let plan = serde_json::to_value(&review(&app).plan).unwrap();
+        let proposed = review(&app).proposed.clone();
+        let source = app.document.bundle().clone();
+        open(&mut app, &host, path);
+        search(&mut app, "@object_102 SA");
+        assert_eq!(
+            app.reference_authoring
+                .opened
+                .as_ref()
+                .unwrap()
+                .chooser
+                .count(),
+            1
+        );
+        assert_eq!(review(&app).recovery_snapshot().unwrap(), before);
+        assert_eq!(serde_json::to_value(&review(&app).plan).unwrap(), plan);
+        assert_eq!(review(&app).proposed, proposed);
+        assert_eq!(app.document.bundle(), &source);
+        let old = event(&app, Action::Choose(Id::from_u128(102)));
+        send_review(
+            &mut app,
+            RowEvent::Select(FacetSelector::Header(HeaderFacet::Name)),
+        );
+        let switched = review(&app).recovery_snapshot().unwrap();
+        let _ = app.update(old);
+        assert_eq!(review(&app).recovery_snapshot().unwrap(), switched);
+        send_review(&mut app, RowEvent::Select(facet));
+        open(&mut app, &host, path);
+        choose(&mut app, Id::from_u128(102));
+        let draft = app.reference_draft(&host, path).unwrap();
+        let mut expected_record = serde_json::to_value(&p.elements[&record]).unwrap();
+        *expected_record.pointer_mut(path).unwrap() = json!(Id::from_u128(102));
+        assert_eq!(draft.materialize().unwrap(), expected_record);
+        assert_eq!(app.document.bundle(), &source);
+        assert!(
+            !app.document.can_undo(),
+            "A choice only stages the active review candidate"
+        );
+    }
+}
+
+mod mounted;
+
+#[test]
+fn review_reference_cannot_reopen_or_write_a_banked_row_after_another_row_takes_focus() {
+    let mut p = Project::empty();
+    for (id, layer) in [
+        (100, Layer::Oa),
+        (101, Layer::Sa),
+        (102, Layer::Sa),
+        (110, Layer::Oa),
+        (111, Layer::Sa),
+    ] {
+        element(
+            &mut p,
+            Id::from_u128(id),
+            Kind::DataType,
+            layer,
+            "Record",
+            None,
+        );
+    }
+    trace(
+        &mut p,
+        Id::from_u128(300),
+        Id::from_u128(100),
+        Id::from_u128(101),
+    );
+    trace(
+        &mut p,
+        Id::from_u128(310),
+        Id::from_u128(110),
+        Id::from_u128(111),
+    );
+    let mut app = App::with_project(p);
+    let _ = app.update(Message::StartSemanticReview(Id::from_u128(300)));
+    let facet = FacetSelector::Data(DataFacet::RecordSupertype);
+    send_review(&mut app, RowEvent::Select(facet.clone()));
+    send_review(
+        &mut app,
+        RowEvent::Decide(facet, Some(SemanticDecision::Candidate)),
+    );
+    let host = review_host(&app);
+    let path = "/body/Sa/Shared/DataType/definition/Record/supertype";
+    let old_open = request(&app, &host, path);
+    open(&mut app, &host, path);
+    let old_choice = event(&app, Action::Choose(Id::from_u128(102)));
+    for event in [
+        semantic_review::Event::ChooseTrace(crate::app::Choice {
+            id: Id::from_u128(310),
+            label: "Second exact trace".into(),
+        }),
+        semantic_review::Event::OpenTrace,
+    ] {
+        let _ = app.update(Message::Workflow(workflow::Event::semantic(event)));
+    }
+    assert_eq!(review(&app).target(app.project()), Some(Id::from_u128(111)));
+    let expected = review(&app).recovery_snapshot().unwrap();
+    let source = app.document.bundle().clone();
+    let _ = app.update(old_choice);
+    let Host::Review { address, facet } = host else {
+        unreachable!()
+    };
+    let _ = app.update(Message::Workflow(workflow::Event::semantic(
+        semantic_review::Event::Row {
+            address,
+            facet: Some(facet),
+            event: RowEvent::ReferenceOpen(old_open),
+        },
+    )));
+    assert!(app.reference_authoring.opened.is_none());
+    assert_eq!(review(&app).recovery_snapshot().unwrap(), expected);
+    assert_eq!(app.document.bundle(), &source);
+    assert!(!app.document.can_undo());
+}

crates/oa-desktop/src/app/reference_authoring/tests/mounted.rs

@@ -0,0 +1,910 @@
+//! Real field + app-root overlay interaction. The null text renderer lets the
+//! same retained widget tree exercise focus and geometry without a GPU/window.
+use super::*;
+use iced::futures::StreamExt;
+use iced::{
+    Element, Event as Input, Point, Size, Theme, Vector,
+    advanced::{
+        Layout, Shell, layout,
+        widget::{Id as WidgetId, Operation, Tree, operation},
+    },
+    keyboard, mouse,
+    widget::{Space, column, container, opaque, scrollable, stack, text_input},
+};
+use oa_core::transitions::TransitionDirection;
+
+#[derive(Default)]
+struct Clipboard;
+impl iced::advanced::Clipboard for Clipboard {
+    fn read(&self, _: iced::advanced::clipboard::Kind) -> Option<String> {
+        None
+    }
+    fn write(&mut self, _: iced::advanced::clipboard::Kind, _: String) {}
+}
+#[derive(Default)]
+struct Fields {
+    values: Vec<(WidgetId, Rectangle, bool)>,
+    scrolls: Vec<(Rectangle, Vector)>,
+}
+impl Operation for Fields {
+    fn traverse(&mut self, visit: &mut dyn FnMut(&mut dyn Operation)) {
+        visit(self);
+    }
+    fn focusable(
+        &mut self,
+        id: Option<&WidgetId>,
+        bounds: Rectangle,
+        state: &mut dyn operation::Focusable,
+    ) {
+        if let Some(id) = id {
+            self.values.push((id.clone(), bounds, state.is_focused()));
+        }
+    }
+    fn scrollable(
+        &mut self,
+        _: Option<&WidgetId>,
+        bounds: Rectangle,
+        _: Rectangle,
+        translation: Vector,
+        _: &mut dyn operation::Scrollable,
+    ) {
+        self.scrolls.push((bounds, translation));
+    }
+}
+impl Fields {
+    fn field(&self, id: &WidgetId) -> (Rectangle, bool) {
+        self.values
+            .iter()
+            .find(|(actual, _, _)| actual == id)
+            .map(|(_, bounds, focused)| (*bounds, *focused))
+            .expect("Mounted field identity")
+    }
+}
+fn view(
+    app: &App,
+    scrolled: bool,
+    nested: bool,
+    show_review: bool,
+) -> Element<'_, Message, Theme, ()> {
+    let draft = app.draft.as_ref().unwrap();
+    let form = column![
+        text_input("Name", &draft.inputs["/name"].raw)
+            .id("before-reference")
+            .on_input(|raw| Message::Field("/name".into(), raw)),
+        adapter::field(draft, app.project(), PATH),
+        text_input("Description", &draft.inputs["/description"].raw)
+            .id("after-reference")
+            .on_input(|raw| Message::Field("/description".into(), raw)),
+    ]
+    .spacing(9);
+    let form = trigger::scope(form, draft.reference_session());
+    let base: Element<'_, Message, Theme, ()> = if scrolled {
+        container(
+            scrollable(column![Space::new().height(500), form])
+                .id("reference-scroll")
+                .height(180),
+        )
+        .width(300)
+        .into()
+    } else {
+        container(form).width(300).height(iced::Fill).into()
+    };
+    let base: Element<'_, Message, Theme, ()> = if nested {
+        scrollable(column![Space::new().height(400), base])
+            .id("outer-reference-scroll")
+            .height(180)
+            .width(300)
+            .into()
+    } else {
+        base
+    };
+    let base = if show_review {
+        let review: Element<'_, Message, Theme, ()> = match app.workflow.as_ref() {
+            Some(workflow::Workflow::Semantic(state)) => {
+                match state.reference_form(app.project()) {
+                    Some(draft) => {
+                        let mut content = column![];
+                        if let Some(raw) = &state.operation_omission {
+                            content = content.push(
+                                text_input("Required engineering rationale", raw)
+                                    .id("review-rationale")
+                                    .on_input(|raw| {
+                                        Message::Workflow(workflow::Event::semantic(
+                                            state.address_event(RowEvent::OperationRationale(raw)),
+                                        ))
+                                    }),
+                            );
+                        }
+                        content = content.push(trigger::scope(
+                            adapter::field(draft, app.project(), "/parent").map(|message| {
+                                match message {
+                                    Message::FieldReferenceOpen(request) => {
+                                        Message::Workflow(workflow::Event::semantic(
+                                            state.address_event(RowEvent::ReferenceOpen(request)),
+                                        ))
+                                    }
+                                    other => other,
+                                }
+                            }),
+                            draft.reference_session(),
+                        ));
+                        opaque(container(trigger::modal(content)).width(300).height(180))
+                    }
+                    None => Space::new().into(),
+                }
+            }
+            _ => Space::new().into(),
+        };
+        stack![base, review].into()
+    } else {
+        base
+    };
+    app.reference_overlay(base)
+}
+struct Mount {
+    tree: Option<Tree>,
+    size: Size,
+    scrolled: bool,
+    nested: bool,
+    show_review: bool,
+}
+impl Default for Mount {
+    fn default() -> Self {
+        Self {
+            tree: None,
+            size: Size::new(360., 320.),
+            scrolled: false,
+            nested: false,
+            show_review: false,
+        }
+    }
+}
+impl Mount {
+    fn frame(
+        &mut self,
+        app: &App,
+        events: &[(Input, Option<Point>)],
+    ) -> (Vec<Message>, Fields, Option<Rectangle>) {
+        let mut view = view(app, self.scrolled, self.nested, self.show_review);
+        let tree = self.tree.get_or_insert_with(|| Tree::new(view.as_widget()));
+        view.as_widget().diff(tree);
+        let node =
+            view.as_widget_mut()
+                .layout(tree, &(), &layout::Limits::new(Size::ZERO, self.size));
+        let viewport = Rectangle::with_size(self.size);
+        let overlay_node = view
+            .as_widget_mut()
+            .overlay(tree, Layout::new(&node), &(), &viewport, Vector::ZERO)
+            .map(|mut overlay| overlay.as_overlay_mut().layout(&(), self.size));
+        let mut messages = Vec::new();
+        for (input, point) in events {
+            let mut shell = Shell::new(&mut messages);
+            let cursor = point.map_or(mouse::Cursor::Unavailable, mouse::Cursor::Available);
+            if let Some(overlay_node) = &overlay_node {
+                let mut overlay = view
+                    .as_widget_mut()
+                    .overlay(tree, Layout::new(&node), &(), &viewport, Vector::ZERO)
+                    .unwrap();
+                overlay.as_overlay_mut().update(
+                    input,
+                    Layout::new(overlay_node),
+                    cursor,
+                    &(),
+                    &mut Clipboard,
+                    &mut shell,
+                );
+                assert!(shell.is_event_captured());
+            } else {
+                view.as_widget_mut().update(
+                    tree,
+                    input,
+                    Layout::new(&node),
+                    cursor,
+                    &(),
+                    &mut Clipboard,
+                    &mut shell,
+                    &viewport,
+                );
+            }
+        }
+        let mut fields = Fields::default();
+        view.as_widget_mut()
+            .operate(tree, Layout::new(&node), &(), &mut fields);
+        (
+            messages,
+            fields,
+            overlay_node.map(|node| node.children()[0].bounds()),
+        )
+    }
+    fn click(&mut self, app: &App, point: Point) -> Vec<Message> {
+        self.frame(
+            app,
+            &[
+                (
+                    Input::Mouse(mouse::Event::ButtonPressed(mouse::Button::Left)),
+                    Some(point),
+                ),
+                (
+                    Input::Mouse(mouse::Event::ButtonReleased(mouse::Button::Left)),
+                    Some(point),
+                ),
+            ],
+        )
+        .0
+    }
+    async fn perform(&mut self, app: &App, task: Task<Message>) {
+        let Some(mut stream) = iced_runtime::task::into_stream(task) else {
+            return;
+        };
+        while let Some(action) = stream.next().await {
+            let iced_runtime::Action::Widget(mut operation) = action else {
+                panic!("Chooser only requests scoped widget focus")
+            };
+            let mut view = view(app, self.scrolled, self.nested, self.show_review);
+            let tree = self.tree.get_or_insert_with(|| Tree::new(view.as_widget()));
+            view.as_widget().diff(tree);
+            let node =
+                view.as_widget_mut()
+                    .layout(tree, &(), &layout::Limits::new(Size::ZERO, self.size));
+            loop {
+                view.as_widget_mut()
+                    .operate(tree, Layout::new(&node), &(), operation.as_mut());
+                match operation.finish() {
+                    operation::Outcome::Chain(next) => operation = next,
+                    _ => break,
+                }
+            }
+        }
+    }
+    async fn dispatch(&mut self, app: &mut App, messages: Vec<Message>) {
+        for message in messages {
+            let task = app.update(message);
+            self.perform(app, task).await;
+        }
+    }
+}
+fn key(key: keyboard::key::Named, shift: bool) -> Input {
+    Input::Keyboard(keyboard::Event::KeyPressed {
+        key: keyboard::Key::Named(key),
+        modified_key: keyboard::Key::Named(key),
+        physical_key: keyboard::key::Physical::Code(keyboard::key::Code::Space),
+        location: keyboard::Location::Standard,
+        modifiers: if shift {
+            keyboard::Modifiers::SHIFT
+        } else {
+            keyboard::Modifiers::empty()
+        },
+        text: None,
+        repeat: false,
+    })
+}
+fn typing(raw: &str) -> Vec<(Input, Option<Point>)> {
+    raw.chars()
+        .map(|character| {
+            let raw = character.to_string();
+            (
+                Input::Keyboard(keyboard::Event::KeyPressed {
+                    key: keyboard::Key::Character(raw.clone().into()),
+                    modified_key: keyboard::Key::Character(raw.clone().into()),
+                    physical_key: keyboard::key::Physical::Code(keyboard::key::Code::KeyA),
+                    location: keyboard::Location::Standard,
+                    modifiers: keyboard::Modifiers::empty(),
+                    text: Some(raw.into()),
+                    repeat: false,
+                }),
+                None,
+            )
+        })
+        .collect()
+}
+
+#[tokio::test]
+async fn mounted_reference_trigger_tabs_to_root_popup_search_escape_and_exact_adjacent_fields() {
+    let mut app = inspector(catalog(), OWNER);
+    let accepted = app.document.bundle().clone();
+    let original = raw(&app);
+    let mut mount = Mount::default();
+    let fields = mount.frame(&app, &[]).1;
+    let messages = mount.click(
+        &app,
+        fields.field(&WidgetId::new("before-reference")).0.center(),
+    );
+    mount.dispatch(&mut app, messages).await;
+    let (_, fields, _) = mount.frame(&app, &[(key(keyboard::key::Named::Tab, false), None)]);
+    let id = trigger::field_id(app.draft.as_ref().unwrap().reference_generation(), PATH);
+    assert!(
+        fields.field(&id).1,
+        "Tab reaches the real reference trigger"
+    );
+    let messages = mount
+        .frame(&app, &[(key(keyboard::key::Named::Enter, false), None)])
+        .0;
+    assert_eq!(messages.len(), 1, "One keyboard activation opens one field");
+    mount.dispatch(&mut app, messages).await;
+    let popup = mount
+        .frame(&app, &[])
+        .2
+        .expect("App root overlay is mounted");
+    assert!(
+        popup.x >= 0.
+            && popup.y >= 0.
+            && popup.x + popup.width <= 360.
+            && popup.y + popup.height <= 320.
+    );
+    let mut inputs = typing("@controller_0720");
+    inputs.push((key(keyboard::key::Named::Escape, false), None));
+    let messages = mount.frame(&app, &inputs).0;
+    mount.dispatch(&mut app, messages).await;
+    let (_, fields, popup) = mount.frame(&app, &[]);
+    assert!(popup.is_none());
+    assert!(
+        fields.field(&id).1,
+        "Escape returns to its exact reference field"
+    );
+    assert_eq!(raw(&app), original);
+    assert_eq!(app.document.bundle(), &accepted);
+    for (backwards, expected) in [(false, "after-reference"), (true, "before-reference")] {
+        let messages = mount.click(&app, fields.field(&id).0.center());
+        mount.dispatch(&mut app, messages).await;
+        let messages = mount
+            .frame(&app, &[(key(keyboard::key::Named::Tab, backwards), None)])
+            .0;
+        mount.dispatch(&mut app, messages).await;
+        let (_, fields, popup) = mount.frame(&app, &[]);
+        assert!(popup.is_none());
+        assert!(
+            fields.field(&WidgetId::new(expected)).1,
+            "Chooser Tab stays within the originating form"
+        );
+    }
+    assert_eq!(app.document.bundle(), &accepted);
+}
+
+#[tokio::test]
+async fn mounted_reference_choice_stages_literal_identity_and_delayed_focus_cannot_hit_replacement_field()
+ {
+    let mut app = inspector(catalog(), OWNER);
+    let accepted = app.document.bundle().clone();
+    let mut mount = Mount::default();
+    let id = trigger::field_id(app.draft.as_ref().unwrap().reference_generation(), PATH);
+    let fields = mount.frame(&app, &[]).1;
+    let messages = mount.click(&app, fields.field(&id).0.center());
+    mount.dispatch(&mut app, messages).await;
+    let messages = mount.frame(&app, &typing("@controller_0720")).0;
+    mount.dispatch(&mut app, messages).await;
+    assert_eq!(
+        app.reference_authoring
+            .opened
+            .as_ref()
+            .unwrap()
+            .chooser
+            .count(),
+        1
+    );
+    let messages = mount
+        .frame(&app, &[(key(keyboard::key::Named::Enter, false), None)])
+        .0;
+    assert_eq!(messages.len(), 1);
+    let delayed_focus = app.update(messages.into_iter().next().unwrap());
+    assert_eq!(
+        app.draft.as_ref().unwrap().value.pointer(PATH),
+        Some(&json!(Id::from_u128(BASE + 720)))
+    );
+    assert_eq!(app.document.bundle(), &accepted);
+    // A structural edit occurs after Choose but before its asynchronous focus.
+    app.draft
+        .as_mut()
+        .unwrap()
+        .shape_scoped(PATH, Value::Null)
+        .unwrap();
+    let fields = mount.frame(&app, &[]).1;
+    let messages = mount.click(
+        &app,
+        fields.field(&WidgetId::new("after-reference")).0.center(),
+    );
+    mount.dispatch(&mut app, messages).await;
+    mount.perform(&app, delayed_focus).await;
+    let fields = mount.frame(&app, &[]).1;
+    assert!(
+        fields.field(&WidgetId::new("after-reference")).1,
+        "A missing old field target makes no focus changes"
+    );
+    assert!(
+        !fields
+            .field(&trigger::field_id(
+                app.draft.as_ref().unwrap().reference_generation(),
+                PATH
+            ))
+            .1
+    );
+    assert_eq!(app.document.bundle(), &accepted);
+}
+
+#[tokio::test]
+async fn mounted_scrolled_reference_anchor_uses_window_geometry_for_pointer_and_keyboard() {
+    let mut app = inspector(catalog(), OWNER);
+    let mut mount = Mount {
+        scrolled: true,
+        ..Default::default()
+    };
+    mount.frame(&app, &[]);
+    mount
+        .perform(
+            &app,
+            iced::widget::operation::snap_to("reference-scroll", scrollable::RelativeOffset::END),
+        )
+        .await;
+    let fields = mount.frame(&app, &[]).1;
+    let id = trigger::field_id(app.draft.as_ref().unwrap().reference_generation(), PATH);
+    let content = fields.field(&id).0;
+    let (viewport, offset) = fields.scrolls[0];
+    assert!(offset.y > 400., "Fixture is genuinely scrolled");
+    let expected = Rectangle {
+        x: content.x - offset.x,
+        y: content.y - offset.y,
+        ..content
+    }
+    .intersection(&viewport)
+    .unwrap();
+    let messages = mount.click(&app, expected.center());
+    let [Message::FieldReferenceOpen(request)] = messages.as_slice() else {
+        panic!("Scrolled field should emit one actual Open")
+    };
+    assert_eq!(request.anchor, expected);
+    mount.dispatch(&mut app, messages).await;
+    let close = app.update(Message::Escape);
+    mount.perform(&app, close).await;
+    let messages = mount
+        .frame(&app, &[(key(keyboard::key::Named::Enter, false), None)])
+        .0;
+    let [Message::FieldReferenceOpen(request)] = messages.as_slice() else {
+        panic!("Focused scrolled field opens without a pointer")
+    };
+    assert_eq!(request.anchor, expected);
+}
+
+#[tokio::test]
+async fn mounted_fresh_tab_reveals_offscreen_reference_and_return_reveals_it_again() {
+    for nested in [false, true] {
+        let mut app = inspector(catalog(), OWNER);
+        let original = raw(&app);
+        let source = app.document.bundle().clone();
+        let mut mount = Mount {
+            scrolled: true,
+            nested,
+            ..Default::default()
+        };
+        let fields = mount.frame(&app, &[]).1;
+        assert!(
+            fields
+                .scrolls
+                .iter()
+                .all(|(_, offset)| *offset == Vector::ZERO)
+        );
+        assert!(fields.field(&WidgetId::new("before-reference")).0.y > 180.);
+        let messages = mount
+            .frame(&app, &[(key(keyboard::key::Named::Tab, false), None)])
+            .0;
+        assert!(
+            messages.is_empty(),
+            "Keyboard reveal must not author any input"
+        );
+        let fields = mount.frame(&app, &[]).1;
+        assert!(fields.field(&WidgetId::new("before-reference")).1);
+        assert!(
+            fields.scrolls.iter().all(|(_, offset)| offset.y > 0.),
+            "Every enclosing viewport reveals fresh focus"
+        );
+        let id = trigger::field_id(app.draft.as_ref().unwrap().reference_generation(), PATH);
+        let offset: f32 = fields.scrolls.iter().map(|(_, offset)| offset.y).sum();
+        assert!(
+            fields.field(&id).0.y - offset >= 180.,
+            "The next reference starts below the fold"
+        );
+        let messages = mount
+            .frame(&app, &[(key(keyboard::key::Named::Tab, false), None)])
+            .0;
+        assert!(messages.is_empty());
+        let fields = mount.frame(&app, &[]).1;
+        let offset: f32 = fields.scrolls.iter().map(|(_, offset)| offset.y).sum();
+        let (bounds, focused) = fields.field(&id);
+        assert!(focused);
+        assert!(bounds.y - offset >= -0.01 && bounds.y + bounds.height - offset <= 180.01);
+        let messages = mount
+            .frame(&app, &[(key(keyboard::key::Named::Enter, false), None)])
+            .0;
+        assert_eq!(
+            messages.len(),
+            1,
+            "A newly revealed field opens through Enter"
+        );
+        mount.dispatch(&mut app, messages).await;
+        let return_focus = app.update(Message::Escape);
+        mount
+            .perform(
+                &app,
+                iced::widget::operation::snap_to(
+                    "reference-scroll",
+                    scrollable::RelativeOffset::START,
+                ),
+            )
+            .await;
+        if nested {
+            mount
+                .perform(
+                    &app,
+                    iced::widget::operation::snap_to(
+                        "outer-reference-scroll",
+                        scrollable::RelativeOffset::START,
+                    ),
+                )
+                .await;
+        }
+        assert!(
+            mount
+                .frame(&app, &[])
+                .1
+                .scrolls
+                .iter()
+                .all(|(_, offset)| *offset == Vector::ZERO)
+        );
+        mount.perform(&app, return_focus).await;
+        let fields = mount.frame(&app, &[]).1;
+        let offset: f32 = fields.scrolls.iter().map(|(_, offset)| offset.y).sum();
+        let (bounds, focused) = fields.field(&id);
+        assert!(
+            focused && bounds.y - offset >= -0.01 && bounds.y + bounds.height - offset <= 180.01
+        );
+        assert_eq!(raw(&app), original);
+        assert_eq!(app.document.bundle(), &source);
+    }
+}
+
+#[tokio::test]
+async fn mounted_form_tab_enters_in_both_directions_and_cycles_boundaries_without_losing_focus() {
+    for backwards in [false, true] {
+        let app = inspector(catalog(), OWNER);
+        let original = raw(&app);
+        let mut mount = Mount::default();
+        let reference = trigger::field_id(app.draft.as_ref().unwrap().reference_generation(), PATH);
+        let forward = [
+            WidgetId::new("before-reference"),
+            reference.clone(),
+            WidgetId::new("after-reference"),
+        ];
+        let reverse = [
+            WidgetId::new("after-reference"),
+            reference,
+            WidgetId::new("before-reference"),
+        ];
+        let expected = if backwards { &reverse } else { &forward };
+        for n in 0..7 {
+            let (messages, fields, popup) =
+                mount.frame(&app, &[(key(keyboard::key::Named::Tab, backwards), None)]);
+            assert!(messages.is_empty() && popup.is_none());
+            assert!(fields.field(&expected[n % 3]).1);
+            assert_eq!(
+                fields
+                    .values
+                    .iter()
+                    .filter(|(_, _, focused)| *focused)
+                    .count(),
+                1
+            );
+        }
+        assert_eq!(raw(&app), original);
+        assert!(!app.document.can_undo());
+    }
+}
+
+#[tokio::test]
+async fn mounted_delayed_return_cannot_focus_under_review_and_fresh_modal_tab_owns_its_form() {
+    let mut p = catalog();
+    trace(&mut p, Id::from_u128(300), OWNER, Id::from_u128(200));
+    let mut app = inspector(p, OWNER);
+    let source = app.document.bundle().clone();
+    let original = raw(&app);
+    let mut mount = Mount {
+        show_review: true,
+        ..Default::default()
+    };
+    let id = trigger::field_id(app.draft.as_ref().unwrap().reference_generation(), PATH);
+    let session = app.draft.as_ref().unwrap().reference_session();
+    let fields = mount.frame(&app, &[]).1;
+    let messages = mount.click(&app, fields.field(&id).0.center());
+    mount.dispatch(&mut app, messages).await;
+    let return_focus = app.update(Message::Escape);
+    let fields = mount.frame(&app, &[]).1;
+    let messages = mount.click(
+        &app,
+        fields.field(&WidgetId::new("after-reference")).0.center(),
+    );
+    mount.dispatch(&mut app, messages).await;
+    let _ = app.update(Message::StartSemanticReview(Id::from_u128(300)));
+    let facet = FacetSelector::Header(HeaderFacet::Parent);
+    send_review(&mut app, RowEvent::Select(facet.clone()));
+    send_review(
+        &mut app,
+        RowEvent::Decide(facet, Some(SemanticDecision::Candidate)),
+    );
+    assert_eq!(
+        app.draft.as_ref().unwrap().reference_session(),
+        session,
+        "Old Inspector really remains mounted"
+    );
+    assert_eq!(
+        trigger::field_id(app.draft.as_ref().unwrap().reference_generation(), PATH),
+        id
+    );
+    let review_before = review(&app).recovery_snapshot().unwrap();
+    let review_field = trigger::field_id(
+        review(&app)
+            .reference_form(app.project())
+            .unwrap()
+            .reference_generation(),
+        "/parent",
+    );
+    mount.perform(&app, return_focus).await;
+    let fields = mount.frame(&app, &[]).1;
+    assert!(
+        !fields.field(&id).1,
+        "A live old field underneath a modal cannot receive the stale focus task"
+    );
+    assert!(fields.field(&WidgetId::new("after-reference")).1);
+    assert!(!fields.field(&review_field).1);
+    let (messages, fields, _) = mount.frame(&app, &[(key(keyboard::key::Named::Tab, false), None)]);
+    assert!(messages.is_empty());
+    assert!(
+        fields.field(&review_field).1,
+        "Review entry ignores retained focus under its modal"
+    );
+    assert!(
+        !fields.field(&WidgetId::new("after-reference")).1,
+        "Modal focus acquisition deactivates background inputs"
+    );
+    let messages = mount.frame(&app, &typing("x")).0;
+    assert!(
+        messages.is_empty(),
+        "A character at the focused Review trigger cannot type into the Inspector below it"
+    );
+    let (messages, fields, _) = mount.frame(&app, &[(key(keyboard::key::Named::Tab, true), None)]);
+    assert!(messages.is_empty());
+    assert!(fields.field(&review_field).1);
+    assert!(!fields.field(&id).1);
+    assert_eq!(review(&app).recovery_snapshot().unwrap(), review_before);
+    assert_eq!(raw(&app), original);
+    assert_eq!(app.document.bundle(), &source);
+}
+
+#[tokio::test]
+async fn mounted_review_pointer_open_and_outside_dismissal_keep_background_input_inactive() {
+    let mut p = catalog();
+    trace(&mut p, Id::from_u128(300), OWNER, Id::from_u128(200));
+    let mut app = inspector(p, OWNER);
+    let original = raw(&app);
+    let source = app.document.bundle().clone();
+    let mut mount = Mount {
+        show_review: true,
+        ..Default::default()
+    };
+    let fields = mount.frame(&app, &[]).1;
+    let messages = mount.click(
+        &app,
+        fields.field(&WidgetId::new("after-reference")).0.center(),
+    );
+    mount.dispatch(&mut app, messages).await;
+    let _ = app.update(Message::StartSemanticReview(Id::from_u128(300)));
+    let facet = FacetSelector::Header(HeaderFacet::Parent);
+    send_review(&mut app, RowEvent::Select(facet.clone()));
+    send_review(
+        &mut app,
+        RowEvent::Decide(facet, Some(SemanticDecision::Candidate)),
+    );
+    let saved = review(&app).recovery_snapshot().unwrap();
+    let id = trigger::field_id(
+        review(&app)
+            .reference_form(app.project())
+            .unwrap()
+            .reference_generation(),
+        "/parent",
+    );
+    let fields = mount.frame(&app, &[]).1;
+    assert!(
+        fields.field(&WidgetId::new("after-reference")).1,
+        "Fixture retains Inspector focus before the modal receives input"
+    );
+    let messages = mount.click(&app, fields.field(&id).0.center());
+    mount.dispatch(&mut app, messages).await;
+    assert!(matches!(
+        &app.reference_authoring.opened.as_ref().unwrap().host,
+        Host::Review { .. }
+    ));
+    let fields = mount.frame(&app, &[]).1;
+    assert!(!fields.field(&WidgetId::new("after-reference")).1);
+    let messages = mount.click(&app, Point::new(359., 319.));
+    assert!(matches!(
+        messages.as_slice(),
+        [Message::Workflow(workflow::Event::Semantic(event))] if matches!(event.as_ref(),
+            semantic_review::Event::Row {
+                event: RowEvent::ReferenceEvent(chooser::Event {
+                    action: Action::Close(Close::Outside),
+                    ..
+                }),
+                ..
+            }
+        )
+    ));
+    for message in messages {
+        let task = app.update(message);
+        assert!(
+            iced_runtime::task::into_stream(task).is_none(),
+            "Outside dismissal must not request focus or apply"
+        );
+    }
+    let (messages, fields, popup) = mount.frame(&app, &typing("x"));
+    assert!(messages.is_empty() && popup.is_none());
+    assert!(!fields.field(&WidgetId::new("after-reference")).1);
+    assert_eq!(review(&app).recovery_snapshot().unwrap(), saved);
+    assert_eq!(raw(&app), original);
+    assert_eq!(app.document.bundle(), &source);
+}
+
+#[tokio::test]
+async fn mounted_reverse_review_required_rationale_remains_editable_beside_candidate_reference_form()
+ {
+    let mut p = persistence::decode(include_bytes!(concat!(
+        env!("CARGO_MANIFEST_DIR"),
+        "/../../harness/fixtures/interface-operation-probe/output/boundary-only.json"
+    )))
+    .unwrap();
+    let sa = p
+        .elements
+        .values()
+        .find(|element| element.alias == "operation_probe_43")
+        .unwrap()
+        .id;
+    let allocation = p
+        .relations
+        .values()
+        .find(|relation| relation.alias == "operation_probe_30")
+        .unwrap()
+        .id;
+    // The boundary fixture deliberately has no selected operation. Author one
+    // through the validated command path before testing reverse omission.
+    let mut message = p.elements[&sa].clone();
+    let Some(SharedBody::Occurrence {
+        body: OccurrenceBody::Exchange { operation, .. },
+        ..
+    }) = message.shared_mut()
+    else {
+        panic!("The operation fixture must contain an Exchange call")
+    };
+    *operation = Some(OperationUse {
+        allocation: Some(allocation),
+    });
+    p = execute_batch(&p, &[Command::EditElement(sa, message)]).unwrap();
+    assert!(matches!(
+        oa_core::operations::resolve(&p, sa).unwrap(),
+        oa_core::operations::OperationResolution::Selected(value)
+            if value.allocation == allocation
+    ));
+    let inspector_id = Id::new_v4();
+    element(
+        &mut p,
+        inspector_id,
+        Kind::DataType,
+        Layer::Oa,
+        "Inspector record",
+        None,
+    );
+    let scenario = p
+        .add_element(Kind::Scenario, Layer::Oa, "Operational counterpart", None)
+        .unwrap();
+    let oa = p
+        .add_element(
+            Kind::Occurrence,
+            Layer::Oa,
+            "Operational message",
+            Some(scenario),
+        )
+        .unwrap();
+    *p.elements.get_mut(&oa).unwrap().shared_mut().unwrap() = SharedBody::Occurrence {
+        body: OccurrenceBody::Exchange {
+            exchange: None,
+            sender: None,
+            receiver: None,
+            message_kind: MessageKind::Asynchronous,
+            reply_to: None,
+            values: vec![],
+            operation: None,
+        },
+        precondition: String::new(),
+        postcondition: String::new(),
+    };
+    p.elements
+        .get_mut(&scenario)
+        .unwrap()
+        .steps_mut()
+        .unwrap()
+        .push(oa);
+    let trace_id = Id::new_v4();
+    trace(&mut p, trace_id, oa, sa);
+    let mut app = inspector(p, inspector_id);
+    let source = app.document.bundle().clone();
+    let inspector_raw = raw(&app);
+    let _ = app.update(Message::StartSemanticReview(trace_id));
+    let _ = app.update(Message::Workflow(workflow::Event::semantic(
+        semantic_review::Event::Direction(TransitionDirection::SaToOa),
+    )));
+    let facet = FacetSelector::Header(HeaderFacet::Parent);
+    send_review(&mut app, RowEvent::Select(facet.clone()));
+    send_review(
+        &mut app,
+        RowEvent::Decide(facet, Some(SemanticDecision::Candidate)),
+    );
+    send_review(&mut app, RowEvent::OperationOmission(true));
+    assert_eq!(review(&app).direction, TransitionDirection::SaToOa);
+    assert_eq!(review(&app).operation_omission.as_deref(), Some(""));
+    let candidate = serde_json::to_value(
+        review(&app)
+            .reference_form(app.project())
+            .unwrap_or_else(|| {
+                panic!(
+                    "Reverse review candidate: selected={:?}, decisions={:?}, error={:?}",
+                    review(&app).selected,
+                    review(&app).decisions,
+                    review(&app).error
+                )
+            })
+            .recovery_snapshot(),
+    )
+    .unwrap();
+    let mut mount = Mount {
+        show_review: true,
+        ..Default::default()
+    };
+    let fields = mount.frame(&app, &[]).1;
+    let messages = mount.click(
+        &app,
+        fields.field(&WidgetId::new("review-rationale")).0.center(),
+    );
+    mount.dispatch(&mut app, messages).await;
+    let messages = mount.frame(&app, &typing("Engineering reason")).0;
+    assert_eq!(
+        messages.len(),
+        "Engineering reason".chars().count(),
+        "Every key reaches the legitimate sibling inside Review"
+    );
+    assert!(messages.iter().all(|message| matches!(
+        message,
+        Message::Workflow(workflow::Event::Semantic(event)) if matches!(event.as_ref(), semantic_review::Event::Row {
+            event: RowEvent::OperationRationale(_),
+            ..
+        })
+    )));
+    mount.dispatch(&mut app, messages).await;
+    assert_eq!(
+        review(&app).operation_omission.as_deref(),
+        Some("Engineering reason")
+    );
+    assert!(
+        mount
+            .frame(&app, &[])
+            .1
+            .field(&WidgetId::new("review-rationale"))
+            .1
+    );
+    assert_eq!(
+        serde_json::to_value(
+            review(&app)
+                .reference_form(app.project())
+                .unwrap()
+                .recovery_snapshot()
+        )
+        .unwrap(),
+        candidate
+    );
+    assert_eq!(raw(&app), inspector_raw);
+    assert_eq!(app.document.bundle(), &source);
+    assert!(!app.document.can_undo());
+}

crates/oa-desktop/src/app/repair_save_state_tests.rs

@@ -0,0 +1,263 @@
+use super::*;
+
+const VALID: &str = concat!(
+    "arcadia 7;\r\n",
+    "project repair \"Repair 救援\" id \"9e8f0000-0000-4000-8000-000000000001\" {\r\n",
+    "    oa_activity assess \"Assess\" id \"9e8f0000-0000-4000-8000-000000000002\" {}\r\n",
+    "}\r\n",
+);
+
+fn open(app: &mut App, path: &std::path::Path) {
+    let _ = app.update(Message::Loaded(Ok(Some(
+        read_snapshot(path.to_owned()).unwrap(),
+    ))));
+}
+
+fn edit(app: &mut App, text: &str) {
+    let _ = app.update(Message::SourceEdit(text_editor::Action::SelectAll));
+    let _ = app.update(Message::SourceEdit(text_editor::Action::Edit(
+        text_editor::Edit::Paste(Arc::new(text.into())),
+    )));
+}
+
+fn save(app: &mut App, path: &std::path::Path) {
+    let receipt = write_snapshot(
+        app.canvas_document,
+        app.document.revision(),
+        app.document.snapshot(),
+        path.to_owned(),
+        app.disk_project.clone(),
+    )
+    .unwrap();
+    let _ = app.update(Message::Saved(Ok(Some(receipt))));
+}
+
+#[test]
+fn repair_to_previous_saved_bytes_requires_save_at_new_destination_and_guards_close() {
+    for extra in [
+        "    include \"missing.arcadia\";\r\n",
+        "    oa_activity assess \"Duplicate\" id \"9e8f0000-0000-4000-8000-000000000003\" {}\r\n",
+    ] {
+        let first = tempfile::tempdir().unwrap();
+        let second = tempfile::tempdir().unwrap();
+        let first_path = first.path().canonicalize().unwrap().join("project.arcadia");
+        let second_path = second
+            .path()
+            .canonicalize()
+            .unwrap()
+            .join("project.arcadia");
+        let invalid = VALID.strip_suffix("}\r\n").unwrap().to_owned() + extra + "}\r\n";
+        std::fs::write(&first_path, VALID).unwrap();
+        std::fs::write(&second_path, &invalid).unwrap();
+        let mut app = App::with_project(Project::empty());
+        open(&mut app, &first_path);
+        assert!(!app.dirty());
+        let before = app.document.snapshot();
+        let revision = app.document.revision();
+        open(&mut app, &second_path);
+        assert!(!app.source_workspace.applied);
+        assert!(Arc::ptr_eq(&before, &app.document.snapshot()));
+        edit(&mut app, VALID);
+        assert!(app.apply_source(), "{}", app.status);
+        assert!(app.source_workspace.applied);
+        assert!(!app.source_dirty());
+        assert_eq!(app.document.bundle(), &before.bundle);
+        assert_eq!(app.project(), &before.decoded.project);
+        assert_eq!(app.document.revision(), revision);
+        assert!(
+            !app.document.can_undo(),
+            "Equal content creates no history step"
+        );
+        assert!(app.document.dirty());
+        assert_eq!(app.hosted_label(), "Unsaved changes");
+        assert_eq!(std::fs::read(&second_path).unwrap(), invalid.as_bytes());
+        assert_eq!(std::fs::read(&first_path).unwrap(), VALID.as_bytes());
+        let close = window::Id::unique();
+        let task = app.update(Message::Request(Pending::Close(close)));
+        assert!(iced_runtime::task::into_stream(task).is_none());
+        assert!(matches!(app.pending, Some(Pending::Close(id)) if id == close));
+        let _ = app.update(Message::Cancel);
+        save(&mut app, &second_path);
+        assert!(!app.dirty());
+        assert_eq!(app.hosted_label(), "All changes saved");
+        assert_eq!(std::fs::read(&second_path).unwrap(), VALID.as_bytes());
+        assert_eq!(std::fs::read(&first_path).unwrap(), VALID.as_bytes());
+    }
+}
+
+#[test]
+fn repair_history_compares_to_new_disk_baseline_and_then_successful_save() {
+    let directory = tempfile::tempdir().unwrap();
+    let path = directory
+        .path()
+        .canonicalize()
+        .unwrap()
+        .join("project.arcadia");
+    std::fs::write(&path, VALID).unwrap();
+    let mut app = App::with_project(Project::empty());
+    open(&mut app, &path);
+    let before = app.document.snapshot();
+    let invalid = format!("{VALID} unfinished {{");
+    std::fs::write(&path, &invalid).unwrap();
+    open(&mut app, &path);
+    let repaired = format!("{VALID}// Repaired rationale\r\n");
+    edit(&mut app, &repaired);
+    assert!(app.apply_source());
+    assert!(app.dirty());
+    let _ = app.update(Message::Undo);
+    assert_eq!(app.document.bundle(), &before.bundle);
+    assert!(
+        app.dirty(),
+        "Old saved bytes are not saved at the repair destination"
+    );
+    let _ = app.update(Message::Redo);
+    assert!(app.dirty());
+    assert_eq!(std::fs::read(&path).unwrap(), invalid.as_bytes());
+
+    std::fs::write(&path, "external edit").unwrap();
+    let failed = write_snapshot(
+        app.canvas_document,
+        app.document.revision(),
+        app.document.snapshot(),
+        path.clone(),
+        app.disk_project.clone(),
+    )
+    .unwrap_err();
+    let _ = app.update(Message::Saved(Err(failed)));
+    assert!(app.dirty());
+    assert_eq!(std::fs::read(&path).unwrap(), b"external edit");
+    std::fs::write(&path, &invalid).unwrap();
+    save(&mut app, &path);
+    assert!(!app.dirty());
+    let _ = app.update(Message::Undo);
+    assert!(app.dirty());
+    assert_eq!(app.document.bundle(), &before.bundle);
+    let _ = app.update(Message::Redo);
+    assert!(!app.dirty(), "Redo to the new saved snapshot is clean");
+    assert_eq!(std::fs::read(&path).unwrap(), repaired.as_bytes());
+}
+
+#[test]
+fn valid_equal_content_at_distinct_destinations_stays_clean() {
+    let first = tempfile::tempdir().unwrap();
+    let second = tempfile::tempdir().unwrap();
+    let first_path = first.path().canonicalize().unwrap().join("project.arcadia");
+    let second_path = second
+        .path()
+        .canonicalize()
+        .unwrap()
+        .join("project.arcadia");
+    std::fs::write(&first_path, VALID).unwrap();
+    std::fs::write(&second_path, VALID).unwrap();
+    let mut app = App::with_project(Project::empty());
+    open(&mut app, &first_path);
+    let before = app.document.bundle().clone();
+    open(&mut app, &second_path);
+    assert_eq!(app.document.bundle(), &before);
+    assert_eq!(app.path.as_ref(), Some(&second_path));
+    assert!(!app.dirty());
+    assert_eq!(app.hosted_label(), "All changes saved");
+}
+
+#[test]
+fn recovering_applied_repair_rebinds_rolled_back_disk_bytes_without_changing_model() {
+    let first = tempfile::tempdir().unwrap();
+    let second = tempfile::tempdir().unwrap();
+    let first_path = first.path().canonicalize().unwrap().join("project.arcadia");
+    let root = second.path().canonicalize().unwrap();
+    let path = root.join("project.arcadia");
+    let before = VALID.replace("Repair 救援", "Before 救援");
+    std::fs::write(&first_path, VALID).unwrap();
+    std::fs::write(&path, VALID).unwrap();
+    let journal = root.join(".arcadia-save-project.arcadia.journal");
+    std::fs::create_dir(&journal).unwrap();
+    std::fs::write(
+        journal.join("journal.json"),
+        br#"{"version":1,"entry":"project.arcadia","files":[{"path":"project.arcadia","before":true,"write":true}]}"#,
+    )
+    .unwrap();
+    std::fs::write(journal.join("0.before"), &before).unwrap();
+    std::fs::write(journal.join("0.after"), VALID).unwrap();
+    let mut app = App::with_project(Project::empty());
+    open(&mut app, &first_path);
+    let accepted = app.document.snapshot();
+    open(&mut app, &path);
+    assert_eq!(app.pending_recovery.as_ref(), Some(&path));
+    assert!(!app.source_workspace.applied);
+    assert!(app.apply_source());
+    assert!(
+        !app.dirty(),
+        "Current bytes still match disk before rollback"
+    );
+    let _ = app.update(Message::SourceRecovered(recover_snapshot(path.clone())));
+    assert!(app.pending_recovery.is_none());
+    assert!(!journal.exists());
+    assert_eq!(std::fs::read(&path).unwrap(), before.as_bytes());
+    assert!(Arc::ptr_eq(&accepted, &app.document.snapshot()));
+    assert!(!app.source_dirty());
+    assert!(app.dirty(), "Recovery changed disk, not the accepted model");
+    assert_eq!(app.hosted_label(), "Unsaved changes");
+    save(&mut app, &path);
+    assert!(!app.dirty());
+    assert_eq!(std::fs::read(&path).unwrap(), VALID.as_bytes());
+}
+
+#[test]
+fn recovery_missing_entry_or_failed_reload_preserves_current_destination_save_authority() {
+    for (current_destination, failed_reload) in
+        [(true, false), (false, false), (true, true), (false, true)]
+    {
+        let directory = tempfile::tempdir().unwrap();
+        let root = directory.path().canonicalize().unwrap();
+        let path = root.join("project.arcadia");
+        std::fs::write(&path, VALID).unwrap();
+        let mut app = App::with_project(Project::empty());
+        open(&mut app, &path);
+        let accepted = app.document.snapshot();
+        let journal = root.join(".arcadia-save-project.arcadia.journal");
+        std::fs::create_dir(&journal).unwrap();
+        std::fs::write(
+            journal.join("journal.json"),
+            br#"{"version":1,"entry":"project.arcadia","files":[{"path":"project.arcadia","before":false,"write":true}]}"#,
+        )
+        .unwrap();
+        std::fs::write(journal.join("0.after"), VALID).unwrap();
+        open(&mut app, &path);
+        assert!(app.apply_source());
+        assert!(!app.dirty());
+        let destination = tempfile::tempdir().unwrap();
+        let saved_elsewhere = destination
+            .path()
+            .canonicalize()
+            .unwrap()
+            .join("project.arcadia");
+        if !current_destination {
+            save(&mut app, &saved_elsewhere);
+            assert_eq!(app.path.as_ref(), Some(&saved_elsewhere));
+            assert_eq!(app.pending_recovery.as_ref(), Some(&path));
+        }
+        let mut receipt = recover_snapshot(path.clone()).unwrap();
+        assert!(
+            receipt.disk.as_ref().unwrap().bundle.files.is_empty(),
+            "Missing entry reloads as an empty repair workspace"
+        );
+        if failed_reload {
+            // Separately exercise the adapter's successful-recovery/failed-read
+            // boundary; first-save rollback itself does not cause a read error.
+            receipt.disk = Err("Injected post-recovery reload failure".into());
+        }
+        let _ = app.update(Message::SourceRecovered(Ok(receipt)));
+        assert!(!path.exists());
+        assert!(!journal.exists());
+        assert!(app.pending_recovery.is_none());
+        assert!(Arc::ptr_eq(&accepted, &app.document.snapshot()));
+        assert_eq!(app.dirty(), current_destination);
+        if current_destination {
+            let _ = app.update(Message::Request(Pending::New));
+            assert!(matches!(app.pending, Some(Pending::New)));
+        } else {
+            assert_eq!(app.path.as_ref(), Some(&saved_elsewhere));
+            assert_eq!(std::fs::read(&saved_elsewhere).unwrap(), VALID.as_bytes());
+        }
+    }
+}

crates/oa-desktop/src/app/review_navigation_tests.rs

@@ -16,7 +16,7 @@ fn state(app: &App) -> &State {
 }
 fn row_event(app: &mut App, event: RowEvent) {
     let event = state(app).address_event(event);
-    send(app, Message::Workflow(Event::Semantic(event)));
+    send(app, Message::Workflow(Event::semantic(event)));
 }
 fn fixture(reverse: bool, destination_view: bool) -> (App, Id, Id, Id, Option<Id>) {
     let mut p = Project::empty();

crates/oa-desktop/src/app/scenario_details_tests.rs

@@ -0,0 +1,279 @@
+//! Actual arrangement selection and current-record Details admission.
+use super::*;
+use crate::behavior::canvas_workspace::tests::Mounted;
+use crate::behavior::scenario::{CanvasEvent, Context, Shelf};
+use crate::behavior::scenario_layout::Representation;
+use iced::{Point, Size, advanced::widget};
+
+const FIXTURE: &str = include_str!("diagram_usages/tests/saved_scenario.arcadia");
+
+fn id(app: &App, alias: &str) -> Id {
+    app.project()
+        .identities()
+        .into_iter()
+        .find(|(_, name)| *name == alias)
+        .unwrap()
+        .0
+}
+fn setup() -> (App, Id, Id, Id) {
+    let mut app = App::with_project(oa_core::language::parse(FIXTURE).unwrap());
+    let a = id(&app, "incident_readable");
+    let b = id(&app, "incident_wide");
+    let owner = id(&app, "incident_response");
+    let _ = app.update(Message::Select(owner));
+    let _ = app.update(Message::Page(Page::Behavior));
+    choose(&mut app, Representation::Saved { diagram: a });
+    let _ = app.update(Message::Select(a));
+    app.window_size = Size::new(1440., 1000.);
+    (app, a, b, owner)
+}
+fn send(app: &mut App, event: impl FnOnce(Context) -> CanvasEvent) {
+    let context = app.scenario_context().unwrap();
+    let _ = app.update(Message::ScenarioCanvas(event(context)));
+}
+fn choose(app: &mut App, representation: Representation) {
+    send(app, |context| {
+        CanvasEvent::Representation(context, representation)
+    });
+}
+fn model_state(app: &App) -> (u64, bool, bool, bool) {
+    (
+        app.document.revision(),
+        app.document.dirty(),
+        app.document.can_undo(),
+        app.document.can_redo(),
+    )
+}
+
+#[tokio::test]
+async fn actual_arrangement_picker_follows_selected_saved_record_and_opens_b_properties() {
+    let (mut app, a, b, _) = setup();
+    let mut mounted = Mounted::new(&mut app).await;
+    let snapshot = app.document.snapshot();
+    let before = model_state(&app);
+    let captured = app.scenario_context().unwrap();
+    let picker = mounted.geometry(&app).bounds("scenario-arrangement-picker");
+    assert!(
+        app.window_size.height - (picker.y + picker.height) > picker.y,
+        "fixture has room for Iced's menu below the actual picker"
+    );
+    assert_eq!(app.selected, a);
+    mounted.click(&mut app, picker.center()).await;
+    // iced_widget 0.14.2 overlay/menu.rs uses default line height plus
+    // vertical padding for each row. The real workspace orders Automatic,
+    // then the fixture's A/B/C Diagram IDs. Select B from the actual overlay.
+    let row_height =
+        f32::from(iced::advanced::text::LineHeight::default().to_absolute(12.into())) + 10.;
+    let b_row = Point::new(
+        picker.center_x(),
+        picker.y + picker.height + row_height * 2.5,
+    );
+    assert!(b_row.y < app.window_size.height);
+    let events = mounted.click(&mut app, b_row).await;
+    assert!(events.iter().any(|event| matches!(event,
+        Message::ScenarioCanvas(CanvasEvent::Representation(context, Representation::Saved { diagram }))
+        if *context == captured && *diagram == b)), "must exercise the actual arrangement callback");
+    assert_eq!(app.selected, b);
+    assert_eq!(app.draft.as_ref().unwrap().original, b);
+    assert_eq!(
+        app.draft.as_ref().unwrap().value["name"],
+        "B - Incident review negative and far"
+    );
+    assert_eq!(app.active_diagram, Some(b));
+    assert_eq!(
+        app.scenario_context().unwrap().representation,
+        Representation::Saved { diagram: b }
+    );
+    assert_ne!(app.scenario_context().unwrap().visit, captured.visit);
+
+    send(&mut app, |context| {
+        CanvasEvent::Shelf(context, Shelf::Selection)
+    });
+    mounted.settle(&mut app).await;
+    let geometry = mounted.geometry(&app);
+    let (details, offset) = geometry.scrolls[&widget::Id::new("scenario-details")];
+    let point = geometry.bounds("scenario-properties").center() - offset;
+    assert!(details.contains(point));
+    let events = mounted.click(&mut app, point).await;
+    assert!(events.iter().any(|event| matches!(event,
+        Message::ScenarioCanvas(CanvasEvent::Properties(_, selected)) if *selected == b)));
+    mounted.settle(&mut app).await;
+    let geometry = mounted.geometry(&app);
+    let (inspector, offset) = geometry.scrolls[&widget::Id::new("inspector")];
+    assert!(
+        geometry
+            .text_inputs
+            .iter()
+            .any(|bounds| inspector.contains(bounds.center() - offset)),
+        "current B Properties must expose an actual editable field"
+    );
+    assert!(
+        !geometry
+            .scrolls
+            .contains_key(&widget::Id::new("scenario-details"))
+    );
+    assert_eq!(
+        app.inspector_tab,
+        crate::navigation::InspectorTab::Properties
+    );
+    assert_eq!(app.selected, b);
+    assert_eq!(app.draft.as_ref().unwrap().original, b);
+    assert!(Arc::ptr_eq(&snapshot, &app.document.snapshot()));
+    assert_eq!(app.project(), &snapshot.decoded.project);
+    assert_eq!(app.document.bundle(), &snapshot.bundle);
+    assert_eq!(model_state(&app), before);
+}
+
+#[test]
+fn arrangement_change_preserves_independent_semantic_and_foreign_view_selection() {
+    for alias in [
+        "initial_report",
+        "reporter",
+        "incident_response",
+        "incident_repair",
+    ] {
+        let (mut app, _, b, _) = setup();
+        let selected = id(&app, alias);
+        let _ = app.update(Message::Select(selected));
+        let snapshot = app.document.snapshot();
+        let before = model_state(&app);
+        choose(&mut app, Representation::Saved { diagram: b });
+        assert_eq!(app.selected, selected, "independent selection {alias}");
+        assert_eq!(app.draft.as_ref().unwrap().original, selected);
+        assert_eq!(app.active_diagram, Some(b));
+        assert!(Arc::ptr_eq(&snapshot, &app.document.snapshot()));
+        assert_eq!(app.document.bundle(), &snapshot.bundle);
+        assert_eq!(model_state(&app), before);
+        if alias == "incident_repair" {
+            assert!(!behavior::scenario::properties_target(
+                app.project(),
+                app.scenario_context().unwrap(),
+                selected
+            ));
+        }
+    }
+}
+
+#[test]
+fn arrangement_follows_view_record_to_automatic_owner_but_not_owner_back_to_saved() {
+    let (mut app, _, b, owner) = setup();
+    let snapshot = app.document.snapshot();
+    let before = model_state(&app);
+    choose(&mut app, Representation::Derived { owner });
+    assert_eq!(app.selected, owner);
+    assert_eq!(app.draft.as_ref().unwrap().original, owner);
+    assert_eq!(app.active_diagram, None);
+    assert!(behavior::scenario::properties_target(
+        app.project(),
+        app.scenario_context().unwrap(),
+        owner
+    ));
+    choose(&mut app, Representation::Saved { diagram: b });
+    assert_eq!(
+        app.selected, owner,
+        "Scenario owner is now independent semantic selection"
+    );
+    assert_eq!(app.draft.as_ref().unwrap().original, owner);
+    assert_eq!(app.active_diagram, Some(b));
+    assert!(Arc::ptr_eq(&snapshot, &app.document.snapshot()));
+    assert_eq!(app.document.bundle(), &snapshot.bundle);
+    assert_eq!(model_state(&app), before);
+}
+
+#[test]
+fn arrangement_applies_only_the_old_view_draft_then_follows_b_with_one_undo() {
+    let (mut app, a, b, _) = setup();
+    let snapshot = app.document.snapshot();
+    let mut expected = app.project().clone();
+    expected.diagrams.get_mut(&a).unwrap().name = "Reviewed A".into();
+    let revision = app.document.revision();
+    let _ = app.update(Message::Field("/name".into(), "Reviewed A".into()));
+    choose(&mut app, Representation::Saved { diagram: b });
+    assert_eq!(app.project(), &expected);
+    assert_eq!(app.selected, b);
+    assert_eq!(app.draft.as_ref().unwrap().original, b);
+    assert!(!app.draft_dirty());
+    assert_eq!(app.document.revision(), revision + 1);
+    let accepted = app.document.snapshot();
+    let _ = app.update(Message::Undo);
+    assert_eq!(app.project(), &snapshot.decoded.project);
+    assert_eq!(app.document.bundle(), &snapshot.bundle);
+    assert!(!app.document.can_undo() && app.document.can_redo());
+    let _ = app.update(Message::Redo);
+    assert_eq!(app.project(), &expected);
+    assert_eq!(app.document.bundle(), &accepted.bundle);
+    assert!(app.document.can_undo() && !app.document.can_redo());
+}
+
+#[test]
+fn same_arrangement_uuid_edit_follows_the_reidentified_record_and_round_trips_source() {
+    let (mut app, a, _, _) = setup();
+    let snapshot = app.document.snapshot();
+    let replacement = Id::parse_str("70200000-0000-4000-8000-000000000099").unwrap();
+    let mut expected = app.project().clone();
+    let mut diagram = expected.diagrams.remove(&a).unwrap();
+    diagram.id = replacement;
+    expected.diagrams.insert(replacement, diagram);
+    let _ = app.update(Message::Field("/id".into(), replacement.to_string()));
+    choose(&mut app, Representation::Saved { diagram: a });
+    assert_eq!(app.project(), &expected);
+    assert_eq!(app.selected, replacement);
+    assert_eq!(app.draft.as_ref().unwrap().original, replacement);
+    assert_eq!(app.active_diagram, Some(replacement));
+    assert_eq!(
+        app.scenario_context().unwrap().representation,
+        Representation::Saved {
+            diagram: replacement
+        }
+    );
+    let accepted = app.document.snapshot();
+    let _ = app.update(Message::Undo);
+    assert_eq!(app.project(), &snapshot.decoded.project);
+    assert_eq!(app.document.bundle(), &snapshot.bundle);
+    assert!(!app.document.can_undo() && app.document.can_redo());
+    let _ = app.update(Message::Redo);
+    assert_eq!(app.project(), &expected);
+    assert_eq!(app.document.bundle(), &accepted.bundle);
+    assert!(!app.document.can_redo());
+}
+
+#[test]
+fn invalid_draft_and_stale_arrangement_preserve_selection_inputs_and_accepted_state() {
+    let (mut app, a, b, _) = setup();
+    let old = app.scenario_context().unwrap();
+    let snapshot = app.document.snapshot();
+    let before = model_state(&app);
+    let _ = app.update(Message::Field("/id".into(), "not-a-uuid".into()));
+    let draft_value = app.draft.as_ref().unwrap().value.clone();
+    choose(&mut app, Representation::Saved { diagram: b });
+    assert_eq!(app.selected, a);
+    assert_eq!(app.active_diagram, Some(a));
+    assert_eq!(
+        app.scenario_context().unwrap().representation,
+        old.representation
+    );
+    assert_eq!(app.draft.as_ref().unwrap().value, draft_value);
+    assert_eq!(app.draft.as_ref().unwrap().inputs["/id"].raw, "not-a-uuid");
+    assert!(app.draft_dirty());
+    assert!(Arc::ptr_eq(&snapshot, &app.document.snapshot()));
+    assert_eq!(model_state(&app), before);
+    let _ = app.update(Message::RevertProperties);
+    choose(&mut app, Representation::Saved { diagram: b });
+    let current = app.scenario_context().unwrap();
+    let _ = app.update(Message::Field("/name".into(), "Retained B input".into()));
+    let selected = app.selected;
+    let _ = app.update(Message::ScenarioCanvas(CanvasEvent::Representation(
+        old,
+        Representation::Saved { diagram: a },
+    )));
+    assert_eq!(app.selected, selected);
+    assert_eq!(app.active_diagram, Some(b));
+    assert_eq!(app.scenario_context().unwrap().visit, current.visit);
+    assert_eq!(
+        app.draft.as_ref().unwrap().inputs["/name"].raw,
+        "Retained B input"
+    );
+    assert!(Arc::ptr_eq(&snapshot, &app.document.snapshot()));
+    assert_eq!(app.document.bundle(), &snapshot.bundle);
+    assert_eq!(model_state(&app), before);
+}

crates/oa-desktop/src/app/scenario_diagram.rs

@@ -0,0 +1,96 @@
+//! Saved Scenario navigation is presentation state, never a document edit.
+use super::*;
+use crate::behavior::scenario_layout::{Representation, presentation::checked_owner};
+
+impl App {
+    pub(super) fn enter_scenario_representation(&mut self, representation: Representation) -> bool {
+        let Some(owner) = checked_owner(self.project(), representation) else {
+            self.status =
+                "This Scenario view is no longer available or has an incompatible owner.".into();
+            return false;
+        };
+        self.layer = self.project().elements[&owner].layer();
+        self.page = Page::Behavior;
+        self.behavior.active_owner = Some(owner);
+        match representation {
+            Representation::Saved { diagram } => self.active_diagram = Some(diagram),
+            Representation::Derived { .. } => {
+                if self
+                    .active_diagram
+                    .is_some_and(|id| self.saved_scenario_diagram(id))
+                {
+                    self.active_diagram = None;
+                }
+            }
+        }
+        self.selected_node = None;
+        if self
+            .behavior
+            .scenario
+            .enter_representation(self.canvas_document, owner, representation)
+        {
+            self.canvas_epoch = self.canvas_epoch.wrapping_add(1);
+        }
+        true
+    }
+
+    /// Reconcile after navigation/adoption without selecting or applying a draft.
+    /// A retained invalid Saved identity remains unavailable; it must not silently
+    /// turn into a different automatic Scenario or another saved arrangement.
+    pub(super) fn reconcile_scenario_workspace(&mut self) {
+        if self.page == Page::Diagram
+            && !self.behavior.has_pending()
+            && let Some(diagram) = self
+                .active_diagram
+                .filter(|id| self.saved_scenario_diagram(*id))
+        {
+            self.enter_scenario_representation(Representation::Saved { diagram });
+        }
+        if self.page != Page::Behavior {
+            self.behavior.scenario.leave();
+            return;
+        }
+        if let Some(rep @ Representation::Saved { diagram }) =
+            self.behavior.scenario.representation()
+        {
+            // The requested view is authoritative until explicit navigation
+            // retires it. This also recovers the same view when Undo restores it.
+            if let Some(owner) = checked_owner(self.project(), rep) {
+                self.active_diagram = Some(diagram);
+                self.layer = self.project().elements[&owner].layer();
+                self.behavior.active_owner = Some(owner);
+                self.behavior
+                    .scenario
+                    .enter_representation(self.canvas_document, owner, rep);
+            } else if let Some(owner) = self.behavior.scenario.owner() {
+                self.behavior
+                    .scenario
+                    .enter_representation(self.canvas_document, owner, rep);
+            }
+            return;
+        }
+        let Some(owner) = behavior::selected_owner(self) else {
+            self.behavior.scenario.leave();
+            return;
+        };
+        if self
+            .project()
+            .elements
+            .get(&owner)
+            .is_some_and(|e| e.kind() == Kind::Scenario)
+        {
+            self.behavior.scenario.enter(self.canvas_document, owner);
+        } else {
+            self.behavior.scenario.leave();
+        }
+    }
+}
+
+#[cfg(test)]
+mod tests;
+
+#[cfg(test)]
+mod adoption_tests;
+
+#[cfg(test)]
+mod owner_navigation_tests;

crates/oa-desktop/src/app/scenario_diagram/adoption_tests.rs

@@ -0,0 +1,264 @@
+//! Independent adoption oracles: expected Projects are edited directly in the
+//! fixture, then admitted through the actual source editor/Document transaction.
+//! Navigation is checked separately from the expected authored mutation.
+use super::*;
+use crate::behavior::canvas_workspace::tests::Mounted;
+use iced::advanced::widget;
+use iced::widget::text_editor;
+use oa_core::language;
+use std::sync::Arc;
+
+struct Fixture {
+    app: App,
+    owner: Id,
+    same_layer: Id,
+    other_layer: Id,
+    view: Id,
+    spare_view: Id,
+}
+
+fn fixture() -> Fixture {
+    let mut project = Project::empty();
+    let owner = project
+        .add_element(Kind::Scenario, Layer::Oa, "Original owner", None)
+        .unwrap();
+    let same_layer = project
+        .add_element(Kind::Scenario, Layer::Oa, "Other OA owner", None)
+        .unwrap();
+    let other_layer = project
+        .add_element(Kind::Scenario, Layer::Sa, "SA owner", None)
+        .unwrap();
+    // A remaining topology makes silent fallback observably different from the
+    // required unavailable Saved view after its owner is deleted.
+    project
+        .add_element(Kind::Process, Layer::Oa, "Remaining process", None)
+        .unwrap();
+    let mut make_view = |alias: &str, name: &str, owner| {
+        let id = Id::new_v4();
+        project.diagrams.insert(
+            id,
+            Diagram {
+                id,
+                alias: alias.into(),
+                name: name.into(),
+                description: String::new(),
+                layer: Layer::Oa,
+                projection: ProjectionKind::Scenario { scenario: owner },
+                layout: None,
+                nodes: Default::default(),
+                routes: vec![],
+                view_options: Default::default(),
+            },
+        );
+        id
+    };
+    let view = make_view("retained_view", "Retained arrangement", owner);
+    let spare_view = make_view("spare_view", "Spare arrangement", same_layer);
+    let mut app = App::with_project(project);
+    let _ = app.update(Message::Select(owner));
+    choose(&mut app, view);
+    assert_saved(&app, view, owner, Layer::Oa);
+    assert!(!app.document.can_undo());
+    Fixture {
+        app,
+        owner,
+        same_layer,
+        other_layer,
+        view,
+        spare_view,
+    }
+}
+
+fn choose(app: &mut App, id: Id) {
+    let _ = app.update(Message::Diagram(Choice {
+        id,
+        label: "Previously captured picker item".into(),
+    }));
+}
+
+fn assert_saved(app: &App, view: Id, owner: Id, layer: Layer) {
+    assert_eq!(app.page, Page::Behavior);
+    assert_eq!(app.layer, layer);
+    assert_eq!(app.active_diagram, Some(view));
+    let context = app
+        .scenario_context()
+        .expect("saved owner remains the visible context");
+    assert_eq!(context.scenario, owner);
+    assert_eq!(
+        context.representation,
+        Representation::Saved { diagram: view }
+    );
+    assert!(!context.visit.is_nil());
+}
+
+fn adopt_from_source(app: &mut App, expected: &Project) {
+    let text = language::format(expected);
+    // Parser equality is a fixture precondition, not the navigation oracle.
+    assert_eq!(language::parse(&text).unwrap(), *expected);
+    let _ = app.update(Message::Page(Page::Text));
+    let _ = app.update(Message::SourceEdit(text_editor::Action::SelectAll));
+    let _ = app.update(Message::SourceEdit(text_editor::Action::Edit(
+        text_editor::Edit::Paste(Arc::new(text)),
+    )));
+    assert!(app.source_dirty());
+    let _ = app.update(Message::ApplySource);
+    assert!(!app.source_dirty(), "{}", app.status);
+    assert_eq!(
+        app.project(),
+        expected,
+        "actual source transaction must adopt exactly the fixture change"
+    );
+    let _ = app.update(Message::Page(Page::Behavior));
+}
+
+fn retarget(cross_layer: bool) {
+    let mut f = fixture();
+    let before = f.app.document.snapshot();
+    let old_context = f.app.scenario_context().unwrap();
+    let revision = f.app.document.revision();
+    let target = if cross_layer {
+        f.other_layer
+    } else {
+        f.same_layer
+    };
+    let layer = if cross_layer { Layer::Sa } else { Layer::Oa };
+    let mut expected = before.decoded.project.clone();
+    let view = expected.diagrams.get_mut(&f.view).unwrap();
+    view.projection = ProjectionKind::Scenario { scenario: target };
+    view.layer = layer;
+
+    adopt_from_source(&mut f.app, &expected);
+    assert_saved(&f.app, f.view, target, layer);
+    assert_ne!(f.app.scenario_context().unwrap().visit, old_context.visit);
+    assert_eq!(
+        f.app.document.revision(),
+        revision + 1,
+        "routing must not create a second transaction"
+    );
+    assert_eq!(
+        f.app.project().diagrams[&f.spare_view],
+        before.decoded.project.diagrams[&f.spare_view]
+    );
+    let adopted_bundle = f.app.document.bundle().clone();
+
+    let _ = f.app.update(Message::Undo);
+    assert_saved(&f.app, f.view, f.owner, Layer::Oa);
+    assert_eq!(f.app.project(), &before.decoded.project);
+    assert_eq!(f.app.document.bundle(), &before.bundle);
+    assert!(
+        !f.app.document.can_undo(),
+        "exactly one authored adoption must be undone"
+    );
+    let _ = f.app.update(Message::Redo);
+    assert_saved(&f.app, f.view, target, layer);
+    assert_eq!(f.app.project(), &expected);
+    assert_eq!(f.app.document.bundle(), &adopted_bundle);
+    assert!(!f.app.document.can_redo());
+}
+
+#[test]
+fn source_same_layer_owner_retarget_undo_redo_keeps_requested_saved_uuid() {
+    retarget(false);
+}
+
+#[test]
+fn source_cross_layer_owner_retarget_undo_redo_keeps_requested_saved_uuid() {
+    retarget(true);
+}
+
+#[tokio::test]
+async fn source_deleted_owner_and_saved_view_mount_unavailable_instead_of_another_behavior() {
+    let mut f = fixture();
+    let before = f.app.document.snapshot();
+    let mut expected = before.decoded.project.clone();
+    assert!(expected.elements.remove(&f.owner).is_some());
+    assert!(expected.diagrams.remove(&f.view).is_some());
+    assert!(expected.elements.contains_key(&f.same_layer));
+    assert!(
+        expected
+            .elements
+            .values()
+            .any(|e| e.kind() == Kind::Process)
+    );
+    adopt_from_source(&mut f.app, &expected);
+    assert_eq!(
+        f.app.behavior.scenario.representation(),
+        Some(Representation::Saved { diagram: f.view })
+    );
+    let adopted = f.app.document.snapshot();
+    let revision = f.app.document.revision();
+    let mut mounted = Mounted::new(&mut f.app).await;
+    let geometry = mounted.geometry(&f.app);
+    assert!(
+        geometry
+            .containers
+            .contains_key(&widget::Id::from("scenario-viewport-unavailable"))
+    );
+    assert!(
+        !geometry
+            .containers
+            .contains_key(&widget::Id::from("scenario-viewport"))
+    );
+    assert_eq!(f.app.project(), &expected);
+    assert_eq!(f.app.document.bundle(), &adopted.bundle);
+    assert_eq!(
+        f.app.document.revision(),
+        revision,
+        "mounting unavailable must remain passive"
+    );
+
+    let _ = f.app.update(Message::Undo);
+    assert_saved(&f.app, f.view, f.owner, Layer::Oa);
+    assert_eq!(f.app.document.bundle(), &before.bundle);
+    let _ = f.app.update(Message::Redo);
+    assert_eq!(
+        f.app.behavior.scenario.representation(),
+        Some(Representation::Saved { diagram: f.view })
+    );
+    mounted.settle(&mut f.app).await;
+    assert!(
+        mounted
+            .geometry(&f.app)
+            .containers
+            .contains_key(&widget::Id::from("scenario-viewport-unavailable"))
+    );
+    assert_eq!(f.app.project(), &expected);
+    assert_eq!(f.app.document.bundle(), &adopted.bundle);
+}
+
+#[test]
+fn missing_and_deleted_picker_ids_cannot_apply_an_unrelated_valid_property_draft() {
+    let mut f = fixture();
+    let mut expected = f.app.project().clone();
+    expected.diagrams.remove(&f.spare_view).unwrap();
+    adopt_from_source(&mut f.app, &expected);
+    let _ = f.app.update(Message::Select(f.owner));
+    let _ = f.app.update(Message::Field(
+        "/name".into(),
+        "Pending valid owner rename".into(),
+    ));
+    assert!(f.app.draft_dirty());
+    let before = f.app.document.snapshot();
+    let revision = f.app.document.revision();
+    let selected = f.app.selected;
+    for invalid in [Id::nil(), f.spare_view] {
+        choose(&mut f.app, invalid);
+        assert_saved(&f.app, f.view, f.owner, Layer::Oa);
+        assert_eq!(f.app.selected, selected);
+        assert!(f.app.draft_dirty());
+        assert_eq!(f.app.project(), &before.decoded.project);
+        assert_eq!(f.app.document.bundle(), &before.bundle);
+        assert_eq!(f.app.document.revision(), revision);
+    }
+    // Establish that the retained draft really was valid, not merely refused by
+    // the property validator: explicit Apply commits it in exactly one step.
+    assert!(f.app.apply(), "{}", f.app.status);
+    assert_eq!(
+        f.app.project().elements[&f.owner].name,
+        "Pending valid owner rename"
+    );
+    assert_eq!(f.app.document.revision(), revision + 1);
+    let _ = f.app.update(Message::Undo);
+    assert_eq!(f.app.project(), &before.decoded.project);
+    assert_eq!(f.app.document.bundle(), &before.bundle);
+}

crates/oa-desktop/src/app/scenario_diagram/owner_navigation_tests.rs

@@ -0,0 +1,116 @@
+//! Explicit owner navigation must retire a retained Saved Scenario, including
+//! when selection was made on a different page. These are real App events.
+use super::*;
+use crate::behavior::scenario::CanvasEvent;
+
+fn setup(kind: Kind) -> (App, Id, Id) {
+    let mut project = Project::empty();
+    let scenario = project
+        .add_element(Kind::Scenario, Layer::Oa, "Incident review", None)
+        .unwrap();
+    let target = project
+        .add_element(kind, Layer::Oa, "Explicit destination", None)
+        .unwrap();
+    let view = Id::new_v4();
+    project.diagrams.insert(
+        view,
+        Diagram {
+            id: view,
+            alias: "incident_saved".into(),
+            name: "Incident saved arrangement".into(),
+            description: String::new(),
+            layer: Layer::Oa,
+            projection: ProjectionKind::Scenario { scenario },
+            layout: None,
+            nodes: Default::default(),
+            routes: vec![],
+            view_options: Default::default(),
+        },
+    );
+    let errors: Vec<_> = oa_core::validation::validate(&project)
+        .into_iter()
+        .filter(|issue| issue.severity == oa_core::validation::Severity::Error)
+        .collect();
+    assert!(errors.is_empty(), "{errors:?}");
+    let mut app = App::with_project(project);
+    let _ = app.update(Message::Select(scenario));
+    let _ = app.update(Message::Diagram(Choice {
+        id: view,
+        label: "Incident saved arrangement".into(),
+    }));
+    assert_eq!(app.page, Page::Behavior);
+    assert_eq!(
+        app.scenario_context().unwrap().representation,
+        Representation::Saved { diagram: view }
+    );
+    assert_eq!(app.selected, scenario);
+    (app, scenario, target)
+}
+
+fn assert_destination(app: &App, target: Id) {
+    assert_eq!(app.page, Page::Behavior);
+    assert_eq!(app.selected, target);
+    assert_eq!(app.behavior.active_owner, Some(target));
+    assert_eq!(behavior::selected_owner(app), Some(target));
+    assert_eq!(
+        app.behavior.scenario.representation(),
+        None,
+        "explicit non-Scenario destination must not retain an overriding Saved request"
+    );
+    assert!(app.scenario_context().is_none());
+}
+
+fn exercise(via_guide: bool) {
+    for kind in [Kind::Process, Kind::StateMachine] {
+        let (mut app, scenario, target) = setup(kind);
+        assert_ne!(scenario, target);
+        let held = app.scenario_context().unwrap();
+        let accepted = app.document.snapshot();
+        let drafts = app.source_workspace.bundle();
+        let revision = app.document.revision();
+        let dirty = (app.document.dirty(), app.dirty(), app.source_dirty());
+        assert!(!app.document.can_undo() && !app.document.can_redo());
+        if via_guide {
+            let _ = app.update(Message::Page(Page::Guide));
+            assert_eq!(app.page, Page::Guide);
+            assert!(app.scenario_context().is_none());
+        }
+        let _ = app.update(Message::Select(target));
+        if via_guide {
+            assert_eq!(
+                app.page,
+                Page::Guide,
+                "explorer selection must not itself switch the page"
+            );
+            let _ = app.update(Message::Page(Page::Behavior));
+        }
+        assert_destination(&app, target);
+        let camera = app.camera_boundary();
+        // The prior saved canvas cannot open its outline after either owner route.
+        let _ = app.update(Message::ScenarioCanvas(CanvasEvent::Shelf(
+            held,
+            crate::behavior::scenario::Shelf::Selection,
+        )));
+        assert_destination(&app, target);
+        assert!(app.camera_boundary() == camera);
+        assert_eq!(app.project(), &accepted.decoded.project);
+        assert_eq!(app.document.bundle(), &accepted.bundle);
+        assert_eq!(app.source_workspace.bundle(), drafts);
+        assert_eq!(app.document.revision(), revision);
+        assert_eq!(
+            (app.document.dirty(), app.dirty(), app.source_dirty()),
+            dirty
+        );
+        assert!(!app.document.can_undo() && !app.document.can_redo());
+    }
+}
+
+#[test]
+fn saved_scenario_guide_selection_returns_to_explicit_process_or_state_owner() {
+    exercise(true);
+}
+
+#[test]
+fn saved_scenario_direct_behavior_selection_enters_explicit_process_or_state_owner() {
+    exercise(false);
+}

crates/oa-desktop/src/app/scenario_diagram/tests.rs

@@ -0,0 +1,205 @@
+use super::*;
+use crate::behavior::scenario::{CanvasEvent, ScrollArea};
+
+fn saved(p: &mut Project, owner: Id, name: &str) -> Id {
+    let id = Id::new_v4();
+    p.diagrams.insert(
+        id,
+        Diagram {
+            id,
+            alias: format!("view_{}", p.diagrams.len()),
+            name: name.into(),
+            description: String::new(),
+            layer: Layer::Oa,
+            projection: ProjectionKind::Scenario { scenario: owner },
+            layout: None,
+            routes: vec![],
+            nodes: Default::default(),
+            view_options: Default::default(),
+        },
+    );
+    id
+}
+fn setup() -> (App, Id, Id, Id, Id) {
+    let (mut p, [owner, callee, _], [reference, _, _]) =
+        behavior::scenario::direct_tests::navigation_fixture();
+    let a = saved(&mut p, owner, "Review A");
+    let b = saved(&mut p, owner, "Review B");
+    let mut app = App::with_project(p);
+    app.select(owner);
+    (app, a, b, reference, callee)
+}
+fn choose(app: &mut App, diagram: Id) {
+    let _ = app.update(Message::Diagram(Choice {
+        id: diagram,
+        label: "Captured view".into(),
+    }));
+}
+fn event(app: &mut App, f: impl FnOnce(behavior::scenario::Context) -> CanvasEvent) {
+    let context = app.scenario_context().unwrap();
+    let _ = app.update(Message::ScenarioCanvas(f(context)));
+}
+#[test]
+fn saved_view_switches_are_distinct_passive_visits_and_preserve_actual_history() {
+    let (mut app, a, b, _, _) = setup();
+    let original = app.document.snapshot();
+    let owner = app.selected;
+    assert!(app.execute(Command::Rename(owner, "Previously edited caller".into())));
+    let edited = app.document.snapshot();
+    let edited_revision = app.document.revision();
+    choose(&mut app, a);
+    let first = app.scenario_context().unwrap();
+    choose(&mut app, b);
+    let second = app.scenario_context().unwrap();
+    choose(&mut app, a);
+    let third = app.scenario_context().unwrap();
+    assert_eq!(first.scenario, owner);
+    assert_eq!(first.representation, Representation::Saved { diagram: a });
+    assert_eq!(second.representation, Representation::Saved { diagram: b });
+    assert_ne!(first.visit, second.visit);
+    assert_ne!(first.visit, third.visit);
+    assert_eq!(app.page, Page::Behavior);
+    assert_eq!(app.selected, owner);
+    assert_eq!(app.document.bundle(), &edited.bundle);
+    assert_eq!(app.project(), &edited.decoded.project);
+    assert_eq!(app.document.revision(), edited_revision);
+    let _ = app.update(Message::Undo);
+    assert_eq!(app.document.bundle(), &original.bundle);
+    assert_eq!(app.project(), &original.decoded.project);
+    let _ = app.update(Message::Redo);
+    assert_eq!(app.document.bundle(), &edited.bundle);
+    assert_eq!(app.project(), &edited.decoded.project);
+}
+#[test]
+fn saved_view_return_rejects_old_passive_events_without_an_intermediate_frame() {
+    let (mut app, a, b, _, _) = setup();
+    choose(&mut app, a);
+    let old = app.scenario_context().unwrap();
+    choose(&mut app, b);
+    choose(&mut app, a);
+    let current = app.scenario_context().unwrap();
+    let camera = app.behavior.scenario.camera_boundary();
+    let before = app.document.snapshot();
+    for stale in [
+        CanvasEvent::Viewport(old, iced::Size::new(432., 321.)),
+        CanvasEvent::Scrolled(old, ScrollArea::Page, iced::Vector::new(0., 800.)),
+        CanvasEvent::FormShown(old, Id::new_v4()),
+        CanvasEvent::Restored(
+            old,
+            Id::new_v4(),
+            ScrollArea::Page,
+            iced::Vector::new(0., 800.),
+        ),
+        CanvasEvent::Camera(
+            old,
+            app.camera_epoch,
+            behavior::canvas_workspace::Event::Pan(iced::Vector::new(90., 80.)),
+        ),
+    ] {
+        let _ = app.update(Message::ScenarioCanvas(stale));
+        assert_eq!(app.scenario_context(), Some(current));
+        assert!(app.behavior.scenario.camera_boundary() == camera);
+        assert_eq!(app.document.bundle(), &before.bundle);
+    }
+}
+#[test]
+fn saved_reference_back_restores_exact_view_with_a_fresh_visit() {
+    let (mut app, a, _, reference, callee) = setup();
+    choose(&mut app, a);
+    let caller = app.scenario_context().unwrap();
+    let before = app.document.snapshot();
+    event(&mut app, |ctx| CanvasEvent::OpenUse(ctx, reference));
+    let target = app.scenario_context().unwrap();
+    assert_eq!(target.scenario, callee);
+    assert_eq!(
+        target.representation,
+        Representation::Derived { owner: callee }
+    );
+    assert_eq!(app.active_diagram, None);
+    event(&mut app, CanvasEvent::Back);
+    let returned = app.scenario_context().unwrap();
+    assert_eq!(returned.representation, caller.representation);
+    assert_eq!(app.active_diagram, Some(a));
+    assert_eq!(app.selected, reference);
+    assert_ne!(returned.visit, caller.visit);
+    assert_eq!(app.document.bundle(), &before.bundle);
+    assert_eq!(app.project(), &before.decoded.project);
+    assert!(!app.document.can_undo());
+}
+#[test]
+fn saved_picker_applies_valid_old_draft_and_uuid_edit_follows_that_same_view() {
+    let (mut app, a, b, _, _) = setup();
+    choose(&mut app, a);
+    let _ = app.update(Message::Select(a));
+    let before = app.document.snapshot();
+    let _ = app.update(Message::Field("/name".into(), "Renamed A".into()));
+    choose(&mut app, b);
+    assert_eq!(app.project().diagrams[&a].name, "Renamed A");
+    assert_eq!(app.selected, b);
+    assert_eq!(
+        app.scenario_context().unwrap().representation,
+        Representation::Saved { diagram: b }
+    );
+    let _ = app.update(Message::Undo);
+    assert_eq!(app.document.bundle(), &before.bundle);
+    choose(&mut app, a);
+    let replacement = Id::new_v4();
+    let _ = app.update(Message::Field("/id".into(), replacement.to_string()));
+    choose(&mut app, a);
+    assert!(!app.project().diagrams.contains_key(&a));
+    assert_eq!(app.active_diagram, Some(replacement));
+    assert_eq!(app.selected, replacement);
+    assert_eq!(
+        app.scenario_context().unwrap().representation,
+        Representation::Saved {
+            diagram: replacement
+        }
+    );
+}
+#[test]
+fn leaving_and_reentering_saved_view_preserves_source_and_retires_passive_visit() {
+    let (mut app, a, _, _, _) = setup();
+    choose(&mut app, a);
+    let old = app.scenario_context().unwrap();
+    let before = app.document.snapshot();
+    let _ = app.update(Message::Page(Page::Guide));
+    assert!(app.scenario_context().is_none());
+    let _ = app.update(Message::Page(Page::Behavior));
+    let fresh = app.scenario_context().unwrap();
+    assert_eq!(fresh.representation, old.representation);
+    assert_ne!(fresh.visit, old.visit);
+    assert_eq!(app.document.bundle(), &before.bundle);
+}
+
+#[test]
+fn arrangement_picker_rejects_previous_visit_and_switches_automatic_without_model_changes() {
+    let (mut app, a, b, _, _) = setup();
+    choose(&mut app, a);
+    let stale = app.scenario_context().unwrap();
+    choose(&mut app, b);
+    let current = app.scenario_context().unwrap();
+    let before = app.document.snapshot();
+    let _ = app.update(Message::ScenarioCanvas(CanvasEvent::Representation(
+        stale,
+        Representation::Saved { diagram: a },
+    )));
+    assert_eq!(app.scenario_context(), Some(current));
+    event(&mut app, |context| {
+        CanvasEvent::Representation(
+            context,
+            Representation::Derived {
+                owner: context.scenario,
+            },
+        )
+    });
+    assert_eq!(
+        app.scenario_context().unwrap().representation,
+        Representation::Derived {
+            owner: current.scenario
+        }
+    );
+    assert_eq!(app.active_diagram, None);
+    assert_eq!(app.document.bundle(), &before.bundle);
+    assert_eq!(app.project(), &before.decoded.project);
+    assert!(!app.document.can_undo());
+}

crates/oa-desktop/src/app/scenario_spacing.rs

@@ -0,0 +1,88 @@
+//! Admit spacing packets before ordinary navigation can retire a newer reveal.
+use super::*;
+use behavior::scenario::spacing::{Event, controller::Finish};
+
+#[cfg(test)]
+mod tests;
+
+impl App {
+    pub(super) fn spacing_enabled(&self) -> bool {
+        self.pending_diagram_reveal.is_none()
+            && !self.behavior.has_pending()
+            && !self.draft_dirty()
+            && !self.source_dirty()
+            && !self.source_rename.open()
+            && behavior::canvas_workspace::keyboard_enabled(self)
+    }
+
+    pub(super) fn scenario_spacing(&mut self, event: Event) -> Task<Message> {
+        let stamp = event.stamp();
+        if self.scenario_context() != Some(stamp.context) || self.camera_epoch != stamp.camera_epoch
+        {
+            return Task::none();
+        }
+        let state = &self.behavior.scenario;
+        let matches =
+            state.spacing_token() == Some(event.token()) && state.spacing_stamp() == Some(stamp);
+        if match event {
+            Event::Begin { token, .. } => token.is_nil() || state.spacing_token().is_some(),
+            _ => !matches,
+        } {
+            return Task::none();
+        }
+        if matches!(event, Event::Cancel { .. }) || !self.spacing_enabled() {
+            if self.behavior.scenario.cancel_spacing() {
+                self.canvas_epoch = self.canvas_epoch.wrapping_add(1);
+            }
+            return Task::none();
+        }
+        match event {
+            Event::Begin { .. } => {
+                let mut state = std::mem::take(&mut self.behavior.scenario);
+                let result = state.begin_spacing(self.project(), event);
+                self.behavior.scenario = state;
+                if result.is_err() {
+                    self.status = "The drag could not start in this view. Try again.".into();
+                }
+            }
+            Event::Move { screen, .. } => self.behavior.scenario.move_spacing(screen),
+            Event::Finish { screen, .. } => {
+                let finished = self.behavior.scenario.finish_spacing(screen);
+                // Retire queued packets even for zero motion or a refused finish.
+                self.canvas_epoch = self.canvas_epoch.wrapping_add(1);
+                match finished {
+                    Ok(Finish::Click(target)) => self.select(target),
+                    Ok(Finish::Noop) => {}
+                    Ok(Finish::Commit {
+                        command,
+                        selected,
+                        scale,
+                        pan,
+                    }) => {
+                        // Document prepares and writes the source candidate before
+                        // committing its snapshot. Failure leaves camera/selection
+                        // and source/history at their accepted values.
+                        match self.document.execute(*command) {
+                            Ok(_) => {
+                                self.selected = selected;
+                                self.selected_node = None;
+                                self.diagram_navigation_focus = None;
+                                self.behavior.scenario.accept_spacing_camera(scale, pan);
+                                self.sync();
+                                self.status = "Scenario spacing updated.".into();
+                            }
+                            Err(error) => self.status = format!("Spacing was not applied: {error}"),
+                        }
+                    }
+                    Err(_) => {
+                        self.status =
+                            "That position cannot be applied. The saved arrangement is unchanged."
+                                .into()
+                    }
+                }
+            }
+            Event::Cancel { .. } => unreachable!(),
+        }
+        Task::none()
+    }
+}

crates/oa-desktop/src/app/scenario_spacing/tests.rs

@@ -0,0 +1,393 @@
+use super::*;
+use behavior::scenario::{
+    CanvasEvent,
+    spacing::{
+        Target,
+        controller::tests::{fixture, packet},
+    },
+};
+use iced::{Point, Size, Vector};
+
+fn setup() -> (App, Id, Id) {
+    let (document, owner, diagram, lane, message) = fixture();
+    let mut app = App::with_project(document.project().clone());
+    let _ = app.update(Message::Select(owner));
+    let _ = app.update(Message::Diagram(Choice {
+        id: diagram,
+        label: "Saved".into(),
+    }));
+    let c = app.scenario_context().unwrap();
+    let _ = app.update(Message::ScenarioCanvas(CanvasEvent::Viewport(
+        c,
+        Size::new(900., 600.),
+    )));
+    assert!(app.spacing_enabled());
+    (app, lane, message)
+}
+
+#[test]
+fn stale_text_and_scenario_messages_do_not_retire_a_new_saved_spacing_gesture() {
+    let (mut app, lane, _) = setup();
+    let previous = app.scenario_context().unwrap();
+    let diagram = match previous.representation {
+        behavior::scenario_layout::Representation::Saved { diagram } => diagram,
+        _ => unreachable!(),
+    };
+    let _ = app.update(Message::Page(Page::Text));
+    let old_indent = Message::SourceIndent(app.source_symbol_context(), false);
+    let old_drawer = Message::TextWorkspace(text_workspace::Event::ShowDrawer(
+        app.text_drawer_context(),
+        text_workspace::DrawerTab::Problems,
+    ));
+    let old_command = app.text_command_message(text_workspace::Command::ShowStatus);
+    let _ = app.update(Message::Diagram(Choice {
+        id: diagram,
+        label: "Saved".into(),
+    }));
+    let context = app.scenario_context().unwrap();
+    assert_ne!(context.visit, previous.visit);
+    let _ = app.update(Message::ScenarioCanvas(CanvasEvent::Viewport(
+        context,
+        Size::new(900., 600.),
+    )));
+    let context = app.scenario_context().unwrap();
+    let (event, start, _) = begin(&mut app, Target::Lane(lane));
+    move_to(&mut app, event, start + Vector::new(24., 0.));
+    let accepted = app.document.snapshot();
+    let source = app.source_workspace.bundle();
+    let source_version = app.source_version;
+    let camera = app.camera_boundary();
+    let selected = app.selected;
+    let events = [
+        old_indent,
+        old_drawer,
+        old_command,
+        Message::ScenarioCanvas(CanvasEvent::Shelf(
+            previous,
+            behavior::scenario::Shelf::Selection,
+        )),
+        Message::ScenarioCanvas(CanvasEvent::Properties(previous, lane)),
+    ];
+    for rejected in events {
+        let _ = app.update(rejected);
+        assert_eq!(app.scenario_context(), Some(context));
+        assert_eq!(app.behavior.scenario.spacing_token(), Some(event.token()));
+        assert_eq!(app.behavior.scenario.spacing_stamp(), Some(event.stamp()));
+        assert!(app.camera_boundary() == camera);
+        assert_eq!(app.selected, selected);
+        assert_eq!(app.source_version, source_version);
+        assert_eq!(app.source_workspace.bundle(), source);
+        assert_eq!(app.document.bundle(), &accepted.bundle);
+        assert_eq!(app.project(), &accepted.decoded.project);
+        assert!(app.text_workspace.drawer().is_none());
+        assert!(!app.document.can_undo() && !app.document.can_redo());
+    }
+    finish(&mut app, event, start + Vector::new(24., 0.));
+    assert!(
+        app.document.can_undo(),
+        "the current gesture remains usable"
+    );
+}
+fn begin(app: &mut App, target: Target) -> (Event, Point, f32) {
+    let event = packet(
+        app.project(),
+        &app.behavior.scenario,
+        app.scenario_context().unwrap(),
+        app.camera_epoch,
+        target,
+    );
+    let Event::Begin {
+        press_screen,
+        scale,
+        ..
+    } = event
+    else {
+        unreachable!()
+    };
+    let _ = app.update(Message::ScenarioCanvas(CanvasEvent::Spacing(event)));
+    assert_eq!(app.behavior.scenario.spacing_token(), Some(event.token()));
+    (event, press_screen, scale)
+}
+fn send(app: &mut App, event: Event) {
+    let _ = app.update(Message::ScenarioCanvas(CanvasEvent::Spacing(event)));
+}
+fn move_to(app: &mut App, begin: Event, screen: Point) {
+    send(
+        app,
+        Event::Move {
+            stamp: begin.stamp(),
+            token: begin.token(),
+            screen,
+        },
+    );
+}
+fn finish(app: &mut App, begin: Event, screen: Point) {
+    send(
+        app,
+        Event::Finish {
+            stamp: begin.stamp(),
+            token: begin.token(),
+            screen,
+        },
+    );
+}
+
+#[test]
+fn same_batch_preview_is_immutable_and_one_commit_undo_redo_has_exact_source_parity() {
+    let (mut app, lane, _) = setup();
+    let original = app.document.snapshot();
+    let source = app.source_workspace.bundle();
+    let selected = app.selected;
+    let epoch = app.canvas_epoch;
+    let (event, start, scale) = begin(&mut app, Target::Lane(lane));
+    move_to(&mut app, event, start + Vector::new(40., 300.));
+    assert_eq!(app.selected, selected);
+    assert_eq!(app.canvas_epoch, epoch);
+    assert_eq!(app.project(), &original.decoded.project);
+    assert_eq!(app.source_workspace.bundle(), source);
+    assert!(!app.document.can_undo() && !app.document.can_redo());
+    finish(&mut app, event, start + Vector::new(40., 300.));
+    assert_eq!(app.selected, lane);
+    assert!(app.document.can_undo() && !app.document.can_redo());
+    let accepted = app.document.snapshot();
+    assert_ne!(accepted.bundle, original.bundle);
+    let expected = behavior::scenario::spacing::controller::tests::expected(
+        &original.decoded.project,
+        match event.stamp().context.representation {
+            behavior::scenario_layout::Representation::Saved { diagram } => diagram,
+            _ => unreachable!(),
+        },
+        Target::Lane(lane),
+        40. / scale,
+    );
+    assert_eq!(app.project(), &expected);
+    let _ = app.update(Message::ShortcutUndo(false));
+    assert_eq!(app.project(), &original.decoded.project);
+    assert_eq!(app.document.bundle(), &original.bundle);
+    assert!(!app.document.can_undo() && app.document.can_redo());
+    let _ = app.update(Message::ShortcutUndo(true));
+    assert_eq!(app.project(), &accepted.decoded.project);
+    assert_eq!(app.document.bundle(), &accepted.bundle);
+}
+
+#[test]
+fn click_selects_but_crossed_return_and_cancel_preserve_selection_camera_and_history() {
+    let (mut app, lane, message) = setup();
+    let original = app.document.snapshot();
+    let camera = app.behavior.scenario.camera_boundary();
+    let (event, start, _) = begin(&mut app, Target::Message(message));
+    finish(&mut app, event, start + Vector::new(30., 2.));
+    assert_eq!(app.selected, message);
+    assert!(camera == app.behavior.scenario.camera_boundary());
+    for cancel in [false, true] {
+        let (event, start, _) = begin(&mut app, Target::Lane(lane));
+        move_to(&mut app, event, start + Vector::new(30., 0.));
+        if cancel {
+            send(
+                &mut app,
+                Event::Cancel {
+                    stamp: event.stamp(),
+                    token: event.token(),
+                },
+            );
+        } else {
+            finish(&mut app, event, start);
+        }
+        assert_eq!(app.selected, message);
+        assert!(camera == app.behavior.scenario.camera_boundary());
+        assert_eq!(app.document.bundle(), &original.bundle);
+        assert_eq!(app.project(), &original.decoded.project);
+        assert!(!app.document.can_undo() && !app.document.can_redo());
+    }
+}
+
+#[test]
+fn stale_finish_after_new_view_and_forged_token_are_inert_before_reveal_reconciliation() {
+    let (mut app, lane, _) = setup();
+    let (event, start, _) = begin(&mut app, Target::Lane(lane));
+    let held_epoch = app.canvas_epoch;
+    send(
+        &mut app,
+        Event::Finish {
+            stamp: event.stamp(),
+            token: Id::new_v4(),
+            screen: start + Vector::new(30., 0.),
+        },
+    );
+    assert_eq!(app.canvas_epoch, held_epoch);
+    assert_eq!(app.behavior.scenario.spacing_token(), Some(event.token()));
+    let owner = event.stamp().context.scenario;
+    let _ = app.update(Message::ScenarioCanvas(CanvasEvent::Representation(
+        event.stamp().context,
+        behavior::scenario_layout::Representation::Derived { owner },
+    )));
+    let current = app.scenario_context();
+    let epoch = app.canvas_epoch;
+    let original = app.document.snapshot();
+    finish(&mut app, event, start + Vector::new(50., 0.));
+    assert_eq!(app.scenario_context(), current);
+    assert_eq!(app.canvas_epoch, epoch);
+    assert!(app.behavior.scenario.spacing_token().is_none());
+    assert_eq!(app.document.bundle(), &original.bundle);
+}
+
+#[test]
+fn source_write_failure_cannot_commit_candidate_or_materialize_camera() {
+    let (mut app, lane, _) = setup();
+    let bundle = app.document.bundle().clone();
+    let mut limits = oa_core::source_project::ProjectLimits::default();
+    limits.model.max_source_bytes = bundle.files.values().map(String::len).sum();
+    app.document = Document::from_bundle(bundle, limits).unwrap();
+    app.sync();
+    let original = app.document.snapshot();
+    let selected = app.selected;
+    let camera = app.behavior.scenario.camera_boundary();
+    let (event, start, _) = begin(&mut app, Target::Lane(lane));
+    move_to(&mut app, event, start + Vector::new(40., 0.));
+    finish(&mut app, event, start + Vector::new(40., 0.));
+    assert!(
+        app.status.starts_with("Spacing was not applied:"),
+        "{}",
+        app.status
+    );
+    assert_eq!(app.selected, selected);
+    assert!(camera == app.behavior.scenario.camera_boundary());
+    assert_eq!(app.project(), &original.decoded.project);
+    assert_eq!(app.document.bundle(), &original.bundle);
+    assert!(!app.document.can_undo() && !app.document.can_redo());
+    assert!(app.behavior.scenario.spacing_token().is_none());
+}
+
+#[test]
+fn pending_semantic_draft_and_source_edit_cancel_and_reject_held_finish() {
+    for source in [false, true] {
+        let (mut app, lane, _) = setup();
+        let original = app.document.snapshot();
+        let selected = app.selected;
+        let (event, start, _) = begin(&mut app, Target::Lane(lane));
+        move_to(&mut app, event, start + Vector::new(30., 0.));
+        if source {
+            let _ = app.update(Message::SourceEdit(text_editor::Action::Edit(
+                text_editor::Edit::Insert(' '),
+            )));
+            assert!(app.source_dirty());
+        } else {
+            let _ = app.update(Message::Behavior(behavior::Event::Scenario(
+                behavior::scenario::Event::Start(
+                    event.stamp().context.scenario,
+                    behavior::scenario::Tool::Lifeline,
+                ),
+            )));
+            assert!(app.behavior.has_pending());
+        }
+        let draft = app.source_workspace.bundle();
+        assert!(app.behavior.scenario.spacing_token().is_none());
+        finish(&mut app, event, start + Vector::new(30., 0.));
+        assert_eq!(app.project(), &original.decoded.project);
+        assert_eq!(app.document.bundle(), &original.bundle);
+        assert_eq!(app.source_workspace.bundle(), draft);
+        assert_eq!(app.selected, selected);
+        assert!(!app.document.can_undo());
+    }
+}
+
+#[test]
+fn stale_finish_cannot_remove_new_same_view_deferred_reveal() {
+    let (mut app, lane, message) = setup();
+    let (event, start, _) = begin(&mut app, Target::Lane(lane));
+    let behavior::scenario_layout::Representation::Saved { diagram } =
+        event.stamp().context.representation
+    else {
+        unreachable!()
+    };
+    let _ = app.update(Message::RevealInDiagram(diagram, message));
+    assert!(app.pending_diagram_reveal.is_some());
+    let epoch = app.canvas_epoch;
+    let selected = app.selected;
+    let visit = app.pending_scenario_reveal_visit;
+    let original = app.document.snapshot();
+    finish(&mut app, event, start + Vector::new(50., 0.));
+    assert_eq!(app.canvas_epoch, epoch);
+    assert_eq!(app.pending_scenario_reveal_visit, visit);
+    assert!(app.pending_diagram_reveal.is_some());
+    assert_eq!(app.selected, selected);
+    assert_eq!(app.document.bundle(), &original.bundle);
+    assert!(!app.document.can_undo());
+}
+
+#[test]
+fn stale_active_actions_cannot_remove_new_same_visit_deferred_reveal() {
+    let (mut app, lane, message) = setup();
+    let old = app.scenario_context().unwrap();
+    let behavior::scenario_layout::Representation::Saved { diagram } = old.representation else {
+        unreachable!()
+    };
+    let accepted = app.document.snapshot();
+    let source = app.source_workspace.bundle();
+    let _ = app.update(Message::RevealInDiagram(diagram, message));
+    let current = app.scenario_context().unwrap();
+    assert_eq!(current.visit, old.visit);
+    assert_eq!(current.representation, old.representation);
+    assert_eq!(current.revision, old.revision);
+    assert_ne!(current.epoch, old.epoch);
+    let pending = app.pending_diagram_reveal.clone();
+    assert!(pending.is_some());
+    let focus = app.diagram_navigation_focus.as_ref().unwrap();
+    let focus = (focus.context, focus.usage.clone(), focus.selected);
+    let camera = app.camera_boundary();
+    for event in [
+        CanvasEvent::Representation(old, old.representation),
+        CanvasEvent::Shelf(old, behavior::scenario::Shelf::Selection),
+        CanvasEvent::Select(old, lane),
+        CanvasEvent::Zoom(old, Some(1.)),
+    ] {
+        let _ = app.update(Message::ScenarioCanvas(event));
+        assert_eq!(app.scenario_context(), Some(current));
+        assert_eq!(app.pending_diagram_reveal, pending);
+        assert_eq!(app.pending_scenario_reveal_visit, Some(current.visit));
+        let actual = app.diagram_navigation_focus.as_ref().unwrap();
+        assert_eq!(
+            (actual.context, actual.usage.clone(), actual.selected),
+            focus
+        );
+        assert!(app.camera_boundary() == camera);
+        assert_eq!(app.selected, message);
+        assert_eq!(app.document.bundle(), &accepted.bundle);
+        assert_eq!(app.project(), &accepted.decoded.project);
+        assert_eq!(app.source_workspace.bundle(), source);
+        assert!(!app.document.can_undo() && !app.document.can_redo());
+    }
+    let _ = app.update(Message::ScenarioCanvas(CanvasEvent::Viewport(
+        current,
+        Size::new(800., 500.),
+    )));
+    assert!(app.pending_diagram_reveal.is_none());
+    assert!(app.pending_scenario_reveal_visit.is_none());
+    assert!(
+        app.diagram_focus(crate::diagram_usage::Surface::Saved(diagram))
+            .is_some()
+    );
+    assert_eq!(app.selected, message);
+    assert_eq!(app.document.bundle(), &accepted.bundle);
+    assert!(!app.document.can_undo() && !app.document.can_redo());
+}
+
+#[test]
+fn modal_open_cancels_preview_and_captured_begin_stays_retired_after_close() {
+    let (mut app, lane, _) = setup();
+    let original = app.document.snapshot();
+    let camera = app.behavior.scenario.camera_boundary();
+    let (event, start, _) = begin(&mut app, Target::Lane(lane));
+    move_to(&mut app, event, start + Vector::new(30., 0.));
+    let _ = app.update(Message::Delete);
+    assert!(app.delete_pending);
+    assert!(app.behavior.scenario.spacing_token().is_none());
+    finish(&mut app, event, start + Vector::new(30., 0.));
+    let _ = app.update(Message::CancelDelete);
+    send(&mut app, event);
+    assert!(app.behavior.scenario.spacing_token().is_none());
+    assert_eq!(app.project(), &original.decoded.project);
+    assert_eq!(app.document.bundle(), &original.bundle);
+    assert!(camera == app.behavior.scenario.camera_boundary());
+    assert!(!app.document.can_undo());
+}