Align traceability placement assertions with captured-view reveal

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-desktop/src/app.rs

@@ -22,6 +22,8 @@ pub(crate) mod source_rename;
 mod source_symbols;
 pub(crate) mod text_workspace;
 #[cfg(test)]
+mod traceability_navigation_tests;
+#[cfg(test)]
 mod transition_context_tests;
 #[cfg(test)]
 mod view_copy_tests;
@@ -359,6 +361,7 @@ pub enum Message {
     Page(Page),
     Guide(crate::guide::Event),
     Traceability(crate::views::traceability::Event),
+    ReviewLayerTraces,
     Behavior(crate::behavior::Event),
     Layer(Layer),
     Select(Id),
@@ -2310,7 +2313,30 @@ impl App {
                         "Apply or revert pending edits before using modeling actions.".into();
                     return Task::none();
                 }
-                self.select(menu.request.object);
+                // Show acts on the diagram captured by the validated menu.
+                // Ordinary cross-layer selection would switch to that element's
+                // preferred same-layer view before the placement command runs.
+                let show_in_mixed_view = matches!(&*action, Message::PlaceSelected)
+                    && self
+                        .active_diagram
+                        .and_then(|id| self.project().diagrams.get(&id))
+                        .is_some_and(|d| {
+                            d.projection == ProjectionKind::Traceability
+                                && self
+                                    .project()
+                                    .elements
+                                    .get(&menu.request.object)
+                                    .is_some_and(|e| {
+                                        e.kind() != Kind::Port && d.projection.includes(e.kind())
+                                    })
+                        });
+                if show_in_mixed_view {
+                    self.selected = menu.request.object;
+                    self.selected_attachment = None;
+                    self.refresh_draft();
+                } else {
+                    self.select(menu.request.object);
+                }
                 self.selected_node = menu.request.placement;
                 self.selected_bend = menu.request.bend.map(|i| (menu.request.object, i));
                 return self.update(*action);
@@ -2508,6 +2534,23 @@ impl App {
                     iced::widget::scrollable::RelativeOffset::START,
                 );
             }
+            Message::ReviewLayerTraces => {
+                // Reuse Page navigation so modal, placement and behavior-form
+                // guards run before changing the transient inventory filter.
+                let navigation = self.update(Message::Page(Page::Traces));
+                if self.page == Page::Traces && !self.behavior.has_pending() {
+                    self.traceability.filter = crate::views::traceability::Filter::Traces;
+                    self.traceability.query.clear();
+                    return Task::batch([
+                        navigation,
+                        iced::widget::operation::snap_to(
+                            "traceability-list",
+                            iced::widget::scrollable::RelativeOffset::START,
+                        ),
+                    ]);
+                }
+                return navigation;
+            }
             Message::Search(value) => {
                 self.search = value;
                 self.explorer_page = 0;

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

@@ -301,6 +301,17 @@ impl App {
                     _ => return Task::none(),
                 };
                 let placing = point.is_none() && matches!(intent, Intent::Create { .. });
+                let filter = if matches!(intent, Intent::Existing { .. })
+                    && self
+                        .project()
+                        .diagrams
+                        .get(&diagram)
+                        .is_some_and(|d| d.projection == ProjectionKind::Traceability)
+                {
+                    Filter::AllCompatible
+                } else {
+                    Filter::Context
+                };
                 let saved = Saved {
                     version: 1,
                     base: oa_core::transitions::project_fingerprint(self.project()),
@@ -309,7 +320,7 @@ impl App {
                     point,
                     placing,
                     query: String::new(),
-                    filter: Filter::Context,
+                    filter,
                     show_placed: false,
                     page: 0,
                 };

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

@@ -1,4 +1,5 @@
 use super::*;
+mod traceability;
 
 fn setup(layer: Layer) -> App {
     let mut app = App::with_project(Project::empty());

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

@@ -0,0 +1,124 @@
+use super::*;
+
+#[test]
+fn traceability_existing_defaults_show_opposite_layer_and_place_only_one_node() {
+    let mut project = Project::empty();
+    let sa = project
+        .add_element(Kind::Function, Layer::Sa, "Deliver report", None)
+        .unwrap();
+    let system = project
+        .add_element(Kind::System, Layer::Sa, "System", None)
+        .unwrap();
+    let diagram = project.ensure_diagram(Layer::Oa);
+    project.diagrams.get_mut(&diagram).unwrap().projection = ProjectionKind::Traceability;
+    let mut app = App::with_project(project);
+    app.page = Page::Diagram;
+    app.layer = Layer::Oa;
+    app.active_diagram = Some(diagram);
+    let before = app.document.snapshot();
+    send(&mut app, Event::Existing(None));
+    assert_eq!(
+        app.architecture.as_ref().unwrap().saved.filter,
+        Filter::AllCompatible
+    );
+    let listed = candidates(&app);
+    assert!(listed.iter().any(|(id, _, shown)| *id == sa && !shown));
+    assert!(listed.iter().any(|(id, _, shown)| *id == system && !shown));
+    send(&mut app, Event::Pick(sa));
+    assert!(app.architecture.as_ref().unwrap().saved.placing);
+    assert_eq!(app.project(), &before.decoded.project);
+    let context = app.route_context().unwrap();
+    let point = Position { x: 345., y: 215. };
+    send(&mut app, Event::Click(context, point));
+    assert!(app.architecture.is_none(), "{}", app.status);
+    assert_eq!(app.active_diagram, Some(diagram));
+    let placed = app.project().diagrams[&diagram]
+        .nodes
+        .values()
+        .find(|n| n.element == sa)
+        .unwrap()
+        .clone();
+    assert_eq!(placed.position, point);
+    let mut expected = before.decoded.project.clone();
+    expected
+        .diagrams
+        .get_mut(&diagram)
+        .unwrap()
+        .nodes
+        .insert(placed.id, placed);
+    assert_eq!(app.project(), &expected);
+    let accepted = app.document.bundle().clone();
+    let _ = app.update(Message::Undo);
+    assert_eq!(app.document.bundle(), &before.bundle);
+    assert!(!app.document.can_undo());
+    let _ = app.update(Message::Redo);
+    assert_eq!(app.project(), &expected);
+    assert_eq!(app.document.bundle(), &accepted);
+}
+
+#[test]
+fn traceability_default_does_not_change_creation_or_ordinary_picker_guards() {
+    let mut app = setup(Layer::Oa);
+    let diagram = app.active_diagram.unwrap();
+    send(&mut app, Event::Existing(None));
+    assert_eq!(
+        app.architecture.as_ref().unwrap().saved.filter,
+        Filter::Context
+    );
+    send(&mut app, Event::Cancel);
+    let _ = app.update(Message::Projection(ProjectionKind::Traceability));
+    send(&mut app, Event::Start(Kind::Entity, None));
+    assert_eq!(
+        app.architecture.as_ref().unwrap().saved.filter,
+        Filter::Context
+    );
+    send(&mut app, Event::Cancel);
+    assert_eq!(app.active_diagram, Some(diagram));
+
+    let mut project = app.project().clone();
+    let sa = project
+        .add_element(Kind::Function, Layer::Sa, "Other layer", None)
+        .unwrap();
+    let port = Id::new_v4();
+    project.elements.insert(
+        port,
+        oa_core::Element {
+            id: port,
+            alias: "legacy_port".into(),
+            name: "Port".into(),
+            description: String::new(),
+            parent: Some(sa),
+            body: ElementBody::shared_in(
+                Layer::Sa,
+                SharedBody::Port {
+                    contract: PortContract::Legacy,
+                    legacy: Some(LegacyPortContract {
+                        direction: PortDirection::InOut,
+                        interface: None,
+                    }),
+                },
+            ),
+        },
+    );
+    oa_core::validate_candidate(&project).unwrap();
+    for projection in [ProjectionKind::Overview, ProjectionKind::Traceability] {
+        let mut p = project.clone();
+        p.diagrams.get_mut(&diagram).unwrap().projection = projection;
+        let mut trial = App::with_project(p);
+        trial.page = Page::Diagram;
+        trial.active_diagram = Some(diagram);
+        trial.layer = Layer::Oa;
+        let before = trial.document.bundle().clone();
+        send(&mut trial, Event::Existing(None));
+        send(&mut trial, Event::Filter(Filter::AllCompatible));
+        assert_eq!(
+            candidates(&trial).iter().any(|(id, _, _)| *id == sa),
+            projection == ProjectionKind::Traceability
+        );
+        assert!(!candidates(&trial).iter().any(|(id, _, _)| *id == port));
+        send(&mut trial, Event::Pick(port));
+        assert!(!trial.architecture.as_ref().unwrap().saved.placing);
+        send(&mut trial, Event::Cancel);
+        assert_eq!(trial.document.bundle(), &before);
+    }
+}

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

@@ -54,6 +54,8 @@ async fn armed() -> (App, Mounted, Id) {
             object: relation,
             placement: None,
             anchor: iced::Point::new(450., 400.),
+            bend: None,
+            route_segment: None,
         },
     );
     mounted.settle(&mut app).await;

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

@@ -0,0 +1,480 @@
+use super::*;
+
+#[test]
+fn state_bend_delayed_commit_after_same_view_selection_is_inert_and_live_commit_works() {
+    let (mut app, _, relation, _) = setup();
+    let context = app.state_context().unwrap();
+    let next = app.project().relations[&relation].target();
+    let waypoints = vec![Position { x: 715., y: -425. }];
+    let delayed = Event::SetBends {
+        context,
+        relation,
+        waypoints: waypoints.clone(),
+    };
+    send(&mut app, Message::Select(next));
+    assert_eq!(app.selected, next);
+    assert_eq!(
+        app.state_context(),
+        Some(context),
+        "same-view selection does not retire the context stamp"
+    );
+    let before = app.document.snapshot();
+    let camera = (
+        app.behavior.diagram.zoom,
+        app.behavior.diagram.pan,
+        app.behavior.diagram.fit,
+    );
+    event(&mut app, delayed);
+    assert_eq!(app.selected, next);
+    assert!(Arc::ptr_eq(&before, &app.document.snapshot()));
+    assert_eq!(app.project(), &before.decoded.project);
+    assert_eq!(app.document.bundle(), &before.bundle);
+    assert!(!app.document.can_undo());
+    assert_eq!(
+        (
+            app.behavior.diagram.zoom,
+            app.behavior.diagram.pan,
+            app.behavior.diagram.fit
+        ),
+        camera
+    );
+    send(&mut app, Message::Select(relation));
+    let context = app.state_context().unwrap();
+    event(
+        &mut app,
+        Event::SetBends {
+            context,
+            relation,
+            waypoints: waypoints.clone(),
+        },
+    );
+    let mut expected = before.decoded.project.clone();
+    let route = expected
+        .diagrams
+        .get_mut(&context.diagram)
+        .unwrap()
+        .routes
+        .iter_mut()
+        .find(|route| route.edge == relation)
+        .unwrap();
+    route.waypoints = waypoints;
+    assert_eq!(app.project(), &expected);
+    assert_source_model_agree(&app);
+    send(&mut app, Message::Undo);
+    assert_eq!(app.document.bundle(), &before.bundle);
+    assert!(
+        !app.document.can_undo(),
+        "live drag remains a single transaction"
+    );
+}
+
+#[test]
+fn state_bend_menu_carries_exact_segment_and_pin_without_changing_delete_action() {
+    let (mut app, _, relation, _) = setup();
+    let context = app.state_context().unwrap();
+    let point = Position { x: 500., y: -400. };
+    event(
+        &mut app,
+        Event::ContextMenu {
+            context,
+            object: relation,
+            placement: None,
+            anchor: iced::Point::ORIGIN,
+            bend: Some(1),
+            route_segment: Some((2, point)),
+        },
+    );
+    let menu = crate::model_menu::popup(&app).unwrap();
+    let mut add = false;
+    let mut remove = false;
+    let mut delete = false;
+    for entry in menu.entries {
+        if let crate::context_menu::Entry::Action {
+            message: Some(Message::Menu(crate::model_menu::Event::Invoke(_, message))),
+            ..
+        } = entry
+        {
+            match *message {
+                Message::StateDiagram(Event::AddBend {
+                    relation: id,
+                    segment: Some((2, at)),
+                    ..
+                }) => {
+                    assert_eq!(id, relation);
+                    assert_eq!(at, point);
+                    add = true;
+                }
+                Message::StateDiagram(Event::RemoveBend {
+                    relation: id,
+                    index: 1,
+                    ..
+                }) => {
+                    assert_eq!(id, relation);
+                    remove = true;
+                }
+                Message::Delete => delete = true,
+                _ => {}
+            }
+        }
+    }
+    assert!(add && remove && delete);
+}
+
+fn setup() -> (App, Id, Id, Id) {
+    let mut f = fixture();
+    let diagram = create_view(&mut f).diagram;
+    let mut project = f.app.project().clone();
+    let relation = project.relate(RelationKind::StateTransition, "Bend trial", f.leaf, f.b);
+    let second = state_edit::create_view(&project, f.machine).unwrap();
+    project = prepare_command(&project, &second.command).unwrap().project;
+    project
+        .diagrams
+        .get_mut(&diagram)
+        .unwrap()
+        .routes
+        .push(EdgeRoute {
+            edge: relation,
+            waypoints: vec![
+                Position { x: 650., y: -400. },
+                Position { x: 300., y: -400. },
+                Position { x: 650., y: -400. },
+            ],
+            label: Some(EdgeLabel {
+                fraction: 0.35,
+                offset: Position { x: 9., y: -23. },
+            }),
+            source_attachment: Some(EdgeAttachment {
+                side: PortAnchorSide::Top,
+                offset: 0.234567,
+            }),
+            target_attachment: Some(EdgeAttachment {
+                side: PortAnchorSide::Bottom,
+                offset: 0.75,
+            }),
+        });
+    let mut app = App::with_project(project);
+    send(&mut app, Message::RevealInDiagram(diagram, relation));
+    (app, diagram, relation, f.a)
+}
+
+#[test]
+fn state_bend_commands_preserve_other_fields_views_and_exact_history() {
+    let (mut app, diagram, relation, _) = setup();
+    let baseline = app.document.snapshot();
+    let points = vec![Position { x: 715., y: 425. }];
+    let mut expected = app.project().clone();
+    expected.diagrams.get_mut(&diagram).unwrap().routes[0].waypoints = points.clone();
+    let context = app.state_context().unwrap();
+    event(
+        &mut app,
+        Event::SetBends {
+            context,
+            relation,
+            waypoints: points.clone(),
+        },
+    );
+    assert_eq!(app.project(), &expected);
+    assert_source_model_agree(&app);
+    let changed = app.document.snapshot();
+    let context = app.state_context().unwrap();
+    event(
+        &mut app,
+        Event::SetBends {
+            context,
+            relation,
+            waypoints: points,
+        },
+    );
+    assert!(
+        Arc::ptr_eq(&changed, &app.document.snapshot()),
+        "equal bends must not add history"
+    );
+    send(&mut app, Message::Undo);
+    assert_eq!(app.project(), &baseline.decoded.project);
+    assert_eq!(app.document.bundle(), &baseline.bundle);
+    assert!(!app.document.can_undo());
+    send(&mut app, Message::Redo);
+    assert_eq!(app.project(), &expected);
+    assert_eq!(app.document.bundle(), &changed.bundle);
+    let context = app.state_context().unwrap();
+    event(&mut app, Event::ClearBends { context, relation });
+    expected.diagrams.get_mut(&diagram).unwrap().routes[0]
+        .waypoints
+        .clear();
+    assert_eq!(app.project(), &expected);
+    let cleared = app.document.snapshot();
+    let context = app.state_context().unwrap();
+    event(&mut app, Event::ClearBends { context, relation });
+    assert!(Arc::ptr_eq(&cleared, &app.document.snapshot()));
+}
+
+#[test]
+fn state_bend_self_loop_add_move_remove_clear_preserves_project_and_source_history() {
+    let (app, diagram, relation, _) = setup();
+    let mut project = app.project().clone();
+    let RelationBody::StateTransition { source, target, .. } =
+        &mut project.relations.get_mut(&relation).unwrap().body
+    else {
+        panic!("State transition fixture")
+    };
+    *target = *source;
+    project.diagrams.get_mut(&diagram).unwrap().routes[0]
+        .waypoints
+        .clear();
+    oa_core::validate_candidate(&project).unwrap();
+    let mut app = App::with_project(project);
+    send(&mut app, Message::RevealInDiagram(diagram, relation));
+    let baseline = app.document.snapshot();
+    let geometry = state_edit::bend_route(app.project(), diagram, relation).unwrap();
+    assert!(!geometry.custom_suspended);
+    assert!(geometry.pins.is_empty());
+    assert!(
+        geometry.points.len() >= 4,
+        "actual external self-loop routing"
+    );
+    let segment = 1;
+    let point = Position {
+        x: (geometry.points[segment].x + geometry.points[segment + 1].x) / 2.,
+        y: (geometry.points[segment].y + geometry.points[segment + 1].y) / 2.,
+    };
+
+    // Each operation must alter only the complete Project's waypoint list;
+    // Undo and Redo must restore exact serialized source, not just geometry.
+    fn check(app: &mut App, diagram: Id, mutation: Event, points: Vec<Position>) {
+        let before = app.document.snapshot();
+        let mut expected = before.decoded.project.clone();
+        expected.diagrams.get_mut(&diagram).unwrap().routes[0].waypoints = points;
+        event(app, mutation);
+        assert_eq!(app.project(), &expected);
+        assert_source_model_agree(app);
+        let after = app.document.snapshot();
+        assert_ne!(after.bundle, before.bundle);
+        send(app, Message::Undo);
+        assert_eq!(app.project(), &before.decoded.project);
+        assert_eq!(app.document.bundle(), &before.bundle);
+        send(app, Message::Redo);
+        assert_eq!(app.project(), &expected);
+        assert_eq!(app.document.bundle(), &after.bundle);
+        assert_source_model_agree(app);
+    }
+
+    let context = app.state_context().unwrap();
+    check(
+        &mut app,
+        diagram,
+        Event::AddBend {
+            context,
+            relation,
+            segment: Some((segment, point)),
+        },
+        vec![point],
+    );
+    let moved = Position {
+        x: point.x + 45.,
+        y: point.y - 35.,
+    };
+    let context = app.state_context().unwrap();
+    check(
+        &mut app,
+        diagram,
+        Event::SetBends {
+            context,
+            relation,
+            waypoints: vec![moved],
+        },
+        vec![moved],
+    );
+    let context = app.state_context().unwrap();
+    check(
+        &mut app,
+        diagram,
+        Event::RemoveBend {
+            context,
+            relation,
+            index: 0,
+        },
+        vec![],
+    );
+    assert_eq!(app.project(), &baseline.decoded.project);
+    send(&mut app, Message::Undo);
+    let context = app.state_context().unwrap();
+    check(
+        &mut app,
+        diagram,
+        Event::ClearBends { context, relation },
+        vec![],
+    );
+    assert_eq!(app.project(), &baseline.decoded.project);
+    assert_source_model_agree(&app);
+    // Clear is a new source-preserving edit and may retain empty-list trivia.
+    // Exact original bytes are restored by history, not by reauthoring a value.
+    for _ in 0..3 {
+        assert!(app.document.can_undo());
+        send(&mut app, Message::Undo);
+    }
+    assert_eq!(app.project(), &baseline.decoded.project);
+    assert_eq!(app.document.bundle(), &baseline.bundle);
+    assert!(!app.document.can_undo());
+}
+
+#[test]
+fn state_bend_insertion_uses_captured_traversal_segment_and_removal_only_changes_pins() {
+    let (app, diagram, relation, _) = setup();
+    let context = app.state_context().unwrap();
+    let p = app.project();
+    let geometry = state_edit::bend_route(p, diagram, relation).unwrap();
+    let original = &p.diagrams[&diagram].routes[0];
+    let reverse = geometry
+        .points
+        .windows(2)
+        .position(|pair| pair[0] == original.waypoints[0] && pair[1] == original.waypoints[1])
+        .unwrap();
+    for (segment, expected_index) in [(reverse, 1), (reverse + 1, 2)] {
+        let point = Position { x: 500., y: -400. };
+        let planned = state_edit::plan(
+            p,
+            context,
+            &Event::AddBend {
+                context,
+                relation,
+                segment: Some((segment, point)),
+            },
+        )
+        .unwrap();
+        let actual = prepare_command(p, &planned.command).unwrap().project;
+        let mut expected = p.clone();
+        expected.diagrams.get_mut(&diagram).unwrap().routes[0]
+            .waypoints
+            .insert(expected_index, point);
+        assert_eq!(actual, expected);
+        let removed = state_edit::plan(
+            &actual,
+            context,
+            &Event::RemoveBend {
+                context,
+                relation,
+                index: expected_index,
+            },
+        )
+        .unwrap();
+        assert_eq!(
+            prepare_command(&actual, &removed.command).unwrap().project,
+            *p
+        );
+    }
+    let default = state_edit::plan(
+        p,
+        context,
+        &Event::AddBend {
+            context,
+            relation,
+            segment: None,
+        },
+    )
+    .unwrap();
+    let Command::SetEdgeRoute { route, .. } = default.command else {
+        panic!("route command")
+    };
+    assert_eq!(route.waypoints.len(), original.waypoints.len() + 1);
+    assert_eq!(route.source_attachment, original.source_attachment);
+    assert_eq!(route.target_attachment, original.target_attachment);
+    assert_eq!(route.label, original.label);
+}
+
+#[test]
+fn state_bend_stale_nonfinite_capacity_hidden_and_folded_requests_are_inert() {
+    let (mut app, diagram, relation, composite) = setup();
+    let context = app.state_context().unwrap();
+    let baseline = app.document.snapshot();
+    for mutation in [
+        Event::SetBends {
+            context: Context {
+                epoch: context.epoch + 1,
+                ..context
+            },
+            relation,
+            waypoints: vec![],
+        },
+        Event::SetBends {
+            context,
+            relation,
+            waypoints: vec![Position { x: f32::NAN, y: 0. }],
+        },
+        Event::SetBends {
+            context,
+            relation,
+            waypoints: vec![Position { x: 0., y: 0. }; 129],
+        },
+        Event::AddBend {
+            context,
+            relation,
+            segment: Some((usize::MAX, Position { x: 0., y: 0. })),
+        },
+        Event::RemoveBend {
+            context,
+            relation,
+            index: usize::MAX,
+        },
+    ] {
+        event(&mut app, mutation);
+        assert!(Arc::ptr_eq(&baseline, &app.document.snapshot()));
+    }
+    let mut p = app.project().clone();
+    p.diagrams.get_mut(&diagram).unwrap().routes[0].waypoints =
+        vec![Position { x: 500., y: -400. }; 128];
+    assert!(
+        state_edit::plan(
+            &p,
+            context,
+            &Event::AddBend {
+                context,
+                relation,
+                segment: Some((1, Position { x: 500., y: -400. }))
+            }
+        )
+        .is_err()
+    );
+    let mut hidden = app.project().clone();
+    hidden
+        .diagrams
+        .get_mut(&diagram)
+        .unwrap()
+        .view_options
+        .hidden_edges
+        .push(relation);
+    assert!(state_edit::bend_route(&hidden, diagram, relation).is_none());
+    assert!(state_edit::plan(&hidden, context, &Event::ClearBends { context, relation }).is_err());
+    let owner = node(&app, diagram, composite);
+    let mut folded = app.project().clone();
+    folded
+        .diagrams
+        .get_mut(&diagram)
+        .unwrap()
+        .nodes
+        .get_mut(&owner)
+        .unwrap()
+        .collapsed = true;
+    assert!(state_edit::bend_route(&folded, diagram, relation).is_none());
+    assert!(state_edit::plan(&folded, context, &Event::ClearBends { context, relation }).is_err());
+    let mut internal = app.project().clone();
+    internal.diagrams.get_mut(&diagram).unwrap().routes.clear();
+    if let RelationBody::StateTransition {
+        source,
+        target,
+        transition_kind,
+        ..
+    } = &mut internal.relations.get_mut(&relation).unwrap().body
+    {
+        *target = *source;
+        *transition_kind = TransitionKind::Internal;
+    }
+    assert!(state_edit::bend_route(&internal, diagram, relation).is_none());
+    send(
+        &mut app,
+        Message::Field("/name".into(), "Unapplied bend owner name".into()),
+    );
+    let draft = app.draft.as_ref().unwrap().value.clone();
+    event(&mut app, Event::ClearBends { context, relation });
+    assert!(Arc::ptr_eq(&baseline, &app.document.snapshot()));
+    assert_eq!(app.draft.as_ref().unwrap().value, draft);
+}

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

@@ -157,10 +157,14 @@ impl App {
                 object,
                 placement,
                 anchor,
+                bend,
+                route_segment,
             } => {
                 let mut request = crate::model_menu::Request::object(object, anchor);
                 request.canvas = Some(context);
                 request.placement = placement;
+                request.bend = bend;
+                request.route_segment = route_segment;
                 return self.handle(Message::Menu(crate::model_menu::Event::Open(request)));
             }
             Event::EditTransition(_, id) => {
@@ -228,6 +232,11 @@ impl App {
                 let Some(context) = self.state_context() else {
                     return Task::none();
                 };
+                if let Event::SetBends { relation, .. } = &mutation
+                    && *relation != self.selected
+                {
+                    return Task::none();
+                }
                 if let Event::SetAttachment {
                     relation,
                     end,
@@ -246,6 +255,14 @@ impl App {
                 }
                 match state_edit::plan(self.project(), context, &mutation) {
                     Ok(plan) => {
+                        if let Command::SetEdgeRoute { diagram, route } = &plan.command
+                            && crate::route_edit::stored_route(
+                                &self.project().diagrams[diagram],
+                                route.edge,
+                            ) == *route
+                        {
+                            return Task::none();
+                        }
                         if self.execute(plan.command) {
                             self.behavior.diagram.diagram = Some(plan.diagram);
                             self.behavior.diagram.placement = plan.placement;

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

@@ -2,6 +2,8 @@
 use super::*;
 #[path = "state_attachment_escape_tests.rs"]
 mod attachment_escape;
+#[path = "state_bend_tests.rs"]
+mod bends;
 use crate::behavior::{
     self,
     state_edit::{self, Context, Endpoint, Event, Tool},

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

@@ -0,0 +1,277 @@
+use super::*;
+use crate::{context_menu::Entry, model_menu, views::traceability::Filter};
+
+fn send(app: &mut App, message: Message) {
+    let _ = app.update(message);
+}
+
+fn fixture() -> (App, Id, Id, Id, Id) {
+    let mut p = Project::empty();
+    let oa = p
+        .add_element(Kind::Activity, Layer::Oa, "Observe", None)
+        .unwrap();
+    let sa = p
+        .add_element(Kind::Function, Layer::Sa, "Detect", None)
+        .unwrap();
+    let mixed = p.ensure_diagram(Layer::Oa);
+    p.diagrams.get_mut(&mixed).unwrap().projection = ProjectionKind::Traceability;
+    p.place(mixed, oa, Position { x: 300., y: 200. });
+    let system = p.ensure_diagram(Layer::Sa);
+    p.place(system, sa, Position { x: 700., y: 200. });
+    oa_core::validate_candidate(&p).unwrap();
+    let mut app = App::with_project(p);
+    app.page = Page::Diagram;
+    app.layer = Layer::Oa;
+    app.active_diagram = Some(mixed);
+    app.selected = oa;
+    app.refresh_draft();
+    app.traceability.filter = Filter::Artifacts;
+    app.traceability.query = "stale artifact query".into();
+    (app, mixed, system, oa, sa)
+}
+
+fn show_action(app: &mut App, element: Id) -> Message {
+    send(app, model_menu::open(element, iced::Point::ORIGIN));
+    model_menu::popup(app)
+        .unwrap()
+        .entries
+        .into_iter()
+        .find_map(|entry| match entry {
+            Entry::Action { label, message, .. } if label == "Show in this diagram" => {
+                Some(message)
+            }
+            _ => None,
+        })
+        .expect("eligible real menu action")
+        .expect("eligible menu action must be enabled")
+}
+
+#[test]
+fn review_layer_traces_resets_inventory_without_applying_property_or_source_drafts() {
+    for source_draft in [false, true] {
+        let (mut app, mixed, _, oa, _) = fixture();
+        if source_draft {
+            send(&mut app, Message::Page(Page::Text));
+            send(
+                &mut app,
+                Message::SourceEdit(iced::widget::text_editor::Action::Edit(
+                    iced::widget::text_editor::Edit::Insert('x'),
+                )),
+            );
+            assert!(app.source_dirty());
+        } else {
+            send(
+                &mut app,
+                Message::Field("/alias".into(), "invalid alias".into()),
+            );
+            assert!(app.draft_dirty());
+        }
+        let raw = serde_json::to_value(app.draft.as_ref().unwrap().recovery_snapshot()).unwrap();
+        let source = app.source_editor.text();
+        let before = app.document.snapshot();
+        let camera = (app.zoom, app.pan);
+        send(&mut app, Message::ReviewLayerTraces);
+        assert_eq!(app.page, Page::Traces);
+        assert_eq!(app.traceability.filter, Filter::Traces);
+        assert!(app.traceability.query.is_empty());
+        assert_eq!(
+            (app.layer, app.active_diagram, app.selected),
+            (Layer::Oa, Some(mixed), oa)
+        );
+        assert_eq!((app.zoom, app.pan), camera);
+        assert_eq!(
+            serde_json::to_value(app.draft.as_ref().unwrap().recovery_snapshot()).unwrap(),
+            raw
+        );
+        assert_eq!(app.source_editor.text(), source);
+        assert!(Arc::ptr_eq(&before, &app.document.snapshot()));
+        assert!(!app.document.can_undo());
+    }
+}
+
+#[test]
+fn review_layer_traces_respects_busy_modal_and_active_placement_guards() {
+    for already_traces in [false, true] {
+        for guard in 0..5 {
+            let (mut app, mixed, _, oa, _) = fixture();
+            match guard {
+                0 => app.busy = true,
+                1 => app.delete_pending = true,
+                2 => app.hosted.visible = true,
+                3 => send(
+                    &mut app,
+                    Message::Architecture(architecture_authoring::Event::Existing(None)),
+                ),
+                4 => {
+                    app.page = Page::Behavior;
+                    let p = app.project().clone();
+                    app.behavior
+                        .creation
+                        .update(&p, behavior::creation::Event::Open(Layer::Oa))
+                        .unwrap();
+                    assert!(app.behavior.has_pending());
+                }
+                _ => unreachable!(),
+            }
+            if already_traces {
+                app.page = Page::Traces;
+            }
+            let original_page = app.page;
+            let before = app.document.snapshot();
+            let behavior_before = app.behavior.recovery_snapshot().unwrap();
+            send(&mut app, Message::ReviewLayerTraces);
+            assert_eq!(
+                app.page, original_page,
+                "guard {guard}, already traces {already_traces}"
+            );
+            assert_eq!(app.traceability.filter, Filter::Artifacts);
+            assert_eq!(app.traceability.query, "stale artifact query");
+            assert_eq!(
+                (app.layer, app.active_diagram, app.selected),
+                (Layer::Oa, Some(mixed), oa)
+            );
+            assert!(Arc::ptr_eq(&before, &app.document.snapshot()));
+            assert_eq!(app.behavior.recovery_snapshot().unwrap(), behavior_before);
+            if guard == 3 {
+                assert!(app.architecture.is_some());
+            }
+        }
+    }
+}
+
+#[test]
+fn mixed_view_show_keeps_its_context_for_every_diagram_app_and_target_layer() {
+    for diagram_layer in [Layer::Oa, Layer::Sa] {
+        for app_layer in [Layer::Oa, Layer::Sa] {
+            for target_layer in [Layer::Oa, Layer::Sa] {
+                let mut p = Project::empty();
+                let oa = p
+                    .add_element(Kind::Activity, Layer::Oa, "Observe", None)
+                    .unwrap();
+                let sa = p
+                    .add_element(Kind::Function, Layer::Sa, "Detect", None)
+                    .unwrap();
+                let target = if target_layer == Layer::Oa { oa } else { sa };
+                let other = if target_layer == Layer::Oa { sa } else { oa };
+                let mixed = p.ensure_diagram(diagram_layer);
+                p.diagrams.get_mut(&mixed).unwrap().projection = ProjectionKind::Traceability;
+                // An attractive same-layer alternative makes accidental
+                // semantic-selection navigation observable in both directions.
+                let mut alternative = p.diagrams[&mixed].clone();
+                alternative.id = Id::new_v4();
+                alternative.alias = "same_layer_alternative".into();
+                alternative.layer = target_layer;
+                alternative.projection = ProjectionKind::Overview;
+                let alternative_id = alternative.id;
+                p.diagrams.insert(alternative_id, alternative);
+                p.place(alternative_id, target, Position { x: 700., y: 200. });
+                oa_core::validate_candidate(&p).unwrap();
+                let mut app = App::with_project(p);
+                app.page = Page::Diagram;
+                app.layer = app_layer;
+                app.active_diagram = Some(mixed);
+                app.selected = other;
+                app.refresh_draft();
+                let before = app.project().clone();
+                let action = show_action(&mut app, target);
+                send(&mut app, action);
+                // The existing RevealInDiagram action synchronizes the layer
+                // to the captured view, even if the prior perspective differed.
+                assert_eq!(
+                    (app.active_diagram, app.layer, app.selected),
+                    (Some(mixed), diagram_layer, target)
+                );
+                let added = app.project().diagrams[&mixed]
+                    .nodes
+                    .values()
+                    .find(|n| n.element == target)
+                    .unwrap()
+                    .clone();
+                assert_eq!(app.selected_node, Some(added.id));
+                let mut expected = before;
+                expected
+                    .diagrams
+                    .get_mut(&mixed)
+                    .unwrap()
+                    .nodes
+                    .insert(added.id, added);
+                assert_eq!(app.project(), &expected);
+            }
+        }
+    }
+}
+
+#[test]
+fn mixed_view_show_menu_places_in_captured_view_with_exact_undo_redo() {
+    let (mut app, mixed, system, _, sa) = fixture();
+    let before = app.document.snapshot();
+    let action = show_action(&mut app, sa);
+    send(&mut app, action);
+    assert_eq!(
+        (app.active_diagram, app.layer, app.selected),
+        (Some(mixed), Layer::Oa, sa)
+    );
+    let added = app.project().diagrams[&mixed]
+        .nodes
+        .values()
+        .find(|n| n.element == sa)
+        .unwrap()
+        .clone();
+    assert_eq!(added.position, Position { x: 60., y: 60. });
+    let mut expected = before.decoded.project.clone();
+    expected
+        .diagrams
+        .get_mut(&mixed)
+        .unwrap()
+        .nodes
+        .insert(added.id, added);
+    assert_eq!(app.project(), &expected);
+    assert_eq!(
+        app.project().diagrams[&system],
+        before.decoded.project.diagrams[&system]
+    );
+    let after = app.document.snapshot();
+    send(&mut app, Message::Undo);
+    assert_eq!(app.project(), &before.decoded.project);
+    assert_eq!(app.document.bundle(), &before.bundle);
+    assert!(!app.document.can_undo());
+    send(&mut app, Message::Redo);
+    assert_eq!(app.project(), &after.decoded.project);
+    assert_eq!(app.document.bundle(), &after.bundle);
+}
+
+#[test]
+fn mixed_view_show_menu_rejects_stale_context_and_pending_property_changes() {
+    for refusal in 0..3 {
+        let (mut app, mixed, system, oa, sa) = fixture();
+        let action = show_action(&mut app, sa);
+        match refusal {
+            0 => app.active_diagram = Some(system),
+            1 => app.canvas_epoch = app.canvas_epoch.wrapping_add(1),
+            2 => {
+                // A queued action must not apply a draft that became dirty
+                // after the menu was rendered, even when its context is valid.
+                app.draft
+                    .as_mut()
+                    .unwrap()
+                    .input("/name", "Unapplied name".into());
+                assert!(app.draft_dirty());
+            }
+            _ => unreachable!(),
+        }
+        let before = app.document.snapshot();
+        let raw = serde_json::to_value(app.draft.as_ref().unwrap().recovery_snapshot()).unwrap();
+        send(&mut app, action);
+        assert!(Arc::ptr_eq(&before, &app.document.snapshot()));
+        assert_eq!(app.selected, oa);
+        assert_eq!(
+            app.active_diagram,
+            Some(if refusal == 0 { system } else { mixed })
+        );
+        assert_eq!(
+            serde_json::to_value(app.draft.as_ref().unwrap().recovery_snapshot()).unwrap(),
+            raw
+        );
+        assert!(!app.document.can_undo());
+    }
+}

crates/oa-desktop/src/behavior/state_bend_tests.rs

@@ -0,0 +1,656 @@
+// Included in state_canvas::tests: exercise the real canvas event path.
+
+fn bend_fixture(authored: bool) -> (Fixture, Id) {
+    let mut f = fixture();
+    let relation = f.project.relate(
+        RelationKind::StateTransition,
+        "Standby to stopped",
+        f.b,
+        f.c,
+    );
+    if authored {
+        f.project
+            .diagrams
+            .get_mut(&f.diagram)
+            .unwrap()
+            .routes
+            .push(EdgeRoute {
+                edge: relation,
+                waypoints: vec![Position {
+                    x: 650.25,
+                    y: 340.75,
+                }],
+                source_attachment: Some(EdgeAttachment {
+                    side: PortAnchorSide::Bottom,
+                    offset: 0.5,
+                }),
+                target_attachment: Some(EdgeAttachment {
+                    side: PortAnchorSide::Top,
+                    offset: 0.25,
+                }),
+                label: Some(EdgeLabel {
+                    fraction: 0.43,
+                    offset: Position { x: 28., y: -16. },
+                }),
+            });
+    }
+    validate_candidate(&f.project).unwrap();
+    (f, relation)
+}
+
+fn bend_segment(scene: &Scene, relation: Id) -> (usize, Point) {
+    let edge = &scene.routed.edges[&relation];
+    edge.points
+        .windows(2)
+        .enumerate()
+        .filter(|(i, _)| *i > 0 && *i + 2 < edge.points.len())
+        .map(|(i, p)| {
+            (
+                i,
+                Point::new((p[0].x + p[1].x) / 2., (p[0].y + p[1].y) / 2.),
+                (p[1].x - p[0].x).abs() + (p[1].y - p[0].y).abs(),
+            )
+        })
+        .filter(|(_, p, length)| {
+            *length > 40. && edge.pins.iter().all(|pin| p.distance(point(*pin)) > 20.)
+        })
+        .max_by(|a, b| a.2.total_cmp(&b.2))
+        .map(|(i, p, _)| (i, p))
+        .expect("fixture has an exposed interior route segment")
+}
+
+fn bend_press(canvas: &StateCanvas<'_>, state: &mut State, at: Point) {
+    motion(canvas, state, at, at);
+    let event = input(
+        canvas,
+        state,
+        mouse::Event::ButtonPressed(mouse::Button::Left),
+        at,
+    );
+    assert!(
+        !matches!(event, Some(Event::SetBends { .. })),
+        "press alone cannot commit"
+    );
+}
+
+#[test]
+fn state_bends_segment_drag_inserts_one_pin_using_ordered_pointer_at_three_zooms() {
+    for zoom in [0.5, 1., 2.] {
+        let (f, relation) = bend_fixture(false);
+        let mut canvas = canvas(&f, Tool::Select, zoom);
+        canvas.selected = relation;
+        let mut state = State::default();
+        let baseline = canvas.scene(&state).unwrap();
+        let (_, midpoint) = bend_segment(&baseline, relation);
+        let start = screen(&canvas, midpoint);
+        let destination = Position {
+            x: ((midpoint.x + 45.) / 5.).round() * 5.,
+            y: ((midpoint.y + 30.) / 5.).round() * 5.,
+        };
+        let release = screen(&canvas, point(destination));
+        let later_batch_cursor = release + Vector::new(137., 83.);
+        motion(&canvas, &mut state, start, later_batch_cursor);
+        input(
+            &canvas,
+            &mut state,
+            mouse::Event::ButtonPressed(mouse::Button::Left),
+            later_batch_cursor,
+        );
+        assert!(f.project.diagrams[&f.diagram].routes.is_empty());
+        motion(&canvas, &mut state, release, later_batch_cursor);
+        assert_eq!(
+            state.bend_preview.as_ref().unwrap().waypoints,
+            vec![destination]
+        );
+        assert_eq!(
+            canvas.scene(&state).unwrap().routed.edges[&relation].pins,
+            vec![destination]
+        );
+        let event = input(
+            &canvas,
+            &mut state,
+            mouse::Event::ButtonReleased(mouse::Button::Left),
+            later_batch_cursor,
+        )
+        .unwrap();
+        assert!(
+            matches!(&event, Event::SetBends { context, relation: id, waypoints }
+            if *context == canvas.context && *id == relation && *waypoints == vec![destination])
+        );
+        assert!(state.bend_preview.is_none());
+        assert!(
+            input(
+                &canvas,
+                &mut state,
+                mouse::Event::ButtonReleased(mouse::Button::Left),
+                later_batch_cursor
+            )
+            .is_none()
+        );
+        let after = prepare_command(
+            &f.project,
+            &state_edit::plan(&f.project, canvas.context, &event)
+                .unwrap()
+                .command,
+        )
+        .unwrap()
+        .project;
+        let stored = &after.diagrams[&f.diagram].routes[0];
+        assert_eq!(stored.waypoints, vec![destination]);
+        assert!(
+            stored.source_attachment.is_none()
+                && stored.target_attachment.is_none()
+                && stored.label.is_none()
+        );
+        assert_eq!(after.relations, f.project.relations);
+    }
+}
+
+#[test]
+fn state_bends_authored_pin_move_preserves_full_project_and_exact_undo_redo() {
+    for zoom in [0.5, 1., 2.] {
+        let (mut f, relation) = bend_fixture(true);
+        let mut other = f.project.diagrams[&f.diagram].clone();
+        other.id = Id::new_v4();
+        other.alias = "bend_reference_view".into();
+        other.nodes = other
+            .nodes
+            .into_values()
+            .map(|mut node| {
+                node.id = Id::new_v4();
+                node.alias = format!("bend_reference_{}", node.alias);
+                (node.id, node)
+            })
+            .collect();
+        let other_id = other.id;
+        f.project.diagrams.insert(other_id, other.clone());
+        validate_candidate(&f.project).unwrap();
+        let original = f.project.diagrams[&f.diagram].routes[0].clone();
+        let mut canvas = canvas(&f, Tool::Select, zoom);
+        canvas.selected = relation;
+        let mut state = State::default();
+        let start = screen(&canvas, point(original.waypoints[0]));
+        let destination = Position { x: 690., y: 365. };
+        let release = screen(&canvas, point(destination));
+        bend_press(&canvas, &mut state, start);
+        motion(&canvas, &mut state, release, release);
+        let preview = state.bend_preview.as_ref().unwrap();
+        let mut intended = original.clone();
+        intended.waypoints[0] = destination;
+        assert_eq!(preview, &intended);
+        assert_eq!(
+            f.project.diagrams[&f.diagram].routes[0], original,
+            "preview is transient"
+        );
+        let preview_scene = canvas.scene(&state).unwrap();
+        let event = input(
+            &canvas,
+            &mut state,
+            mouse::Event::ButtonReleased(mouse::Button::Left),
+            release,
+        )
+        .unwrap();
+        assert!(
+            matches!(&event, Event::SetBends { waypoints, .. } if waypoints == &intended.waypoints)
+        );
+        let plan = state_edit::plan(&f.project, canvas.context, &event).unwrap();
+        let mut expected = f.project.clone();
+        expected.diagrams.get_mut(&f.diagram).unwrap().routes[0] = intended;
+        let mut document = Document::from_project(f.project.clone(), Default::default()).unwrap();
+        let before = document.bundle().clone();
+        document.execute(plan.command).unwrap();
+        assert_eq!(document.project(), &expected);
+        assert_eq!(document.project().diagrams[&other_id], other);
+        let committed_view = projection::project_view(document.project(), f.diagram);
+        let committed = routing::route_diagram(
+            document.project(),
+            &document.project().diagrams[&f.diagram],
+            &committed_view,
+        );
+        let preview_edge = &preview_scene.routed.edges[&relation];
+        let committed_edge = &committed.edges[&relation];
+        assert_eq!(preview_edge.points, committed_edge.points);
+        assert_eq!(preview_edge.pin_fractions, committed_edge.pin_fractions);
+        assert_eq!(preview_edge.warnings, committed_edge.warnings);
+        let edited = document.bundle().clone();
+        assert!(document.undo());
+        assert_eq!(document.project(), &f.project);
+        assert_eq!(document.bundle(), &before);
+        assert!(!document.undo(), "one drag adds one history operation");
+        assert!(document.redo());
+        assert_eq!(document.project(), &expected);
+        assert_eq!(document.bundle(), &edited);
+        assert!(!document.redo());
+    }
+}
+
+#[test]
+fn state_bends_stationary_and_out_and_back_restore_off_grid_or_automatic_route() {
+    for authored in [false, true] {
+        for zoom in [0.5, 1., 2.] {
+            for travel in [false, true] {
+                let (f, relation) = bend_fixture(authored);
+                let mut canvas = canvas(&f, Tool::Select, zoom);
+                canvas.selected = relation;
+                let mut state = State::default();
+                let scene = canvas.scene(&state).unwrap();
+                let world = if authored {
+                    point(scene.routed.edges[&relation].pins[0])
+                } else {
+                    bend_segment(&scene, relation).1
+                };
+                let start = screen(&canvas, world);
+                bend_press(&canvas, &mut state, start);
+                if travel {
+                    let away = start + Vector::new(45., 30.) * zoom;
+                    motion(&canvas, &mut state, away, away);
+                    assert!(state.bend_preview.is_some());
+                    motion(&canvas, &mut state, start, start);
+                }
+                assert!(
+                    input(
+                        &canvas,
+                        &mut state,
+                        mouse::Event::ButtonReleased(mouse::Button::Left),
+                        start
+                    )
+                    .is_none()
+                );
+                assert!(state.bend_preview.is_none());
+                assert_eq!(
+                    canvas.scene(&state).unwrap().routed.edges[&relation].points,
+                    scene.routed.edges[&relation].points
+                );
+                assert_eq!(
+                    f.project.diagrams[&f.diagram].routes.len(),
+                    usize::from(authored)
+                );
+                if authored {
+                    assert_eq!(
+                        f.project.diagrams[&f.diagram].routes[0].waypoints,
+                        vec![Position {
+                            x: 650.25,
+                            y: 340.75
+                        }]
+                    );
+                }
+            }
+        }
+    }
+}
+
+#[test]
+fn state_bends_cancel_on_camera_context_focus_and_pointer_interruptions() {
+    for cancellation in 0..16 {
+        let (f, relation) = bend_fixture(true);
+        let mut canvas = canvas(&f, Tool::Select, 1.);
+        canvas.selected = relation;
+        let mut state = State::default();
+        let original = f.project.diagrams[&f.diagram].routes[0].clone();
+        let start = screen(&canvas, point(original.waypoints[0]));
+        let release = start + Vector::new(45., 30.);
+        bend_press(&canvas, &mut state, start);
+        motion(&canvas, &mut state, release, release);
+        assert!(state.bend_preview.is_some(), "case {cancellation}");
+        let mut release_bounds = bounds();
+        match cancellation {
+            0 => canvas.zoom = 2.,
+            1 => canvas.pan.x += 10.,
+            2 => canvas.context.epoch += 1,
+            3 => canvas.context.revision += 1,
+            4 => canvas.context.document = Id::new_v4(),
+            5 => canvas.tool = Tool::Transition,
+            6 => canvas.editable = false,
+            7 | 8 => {
+                input(
+                    &canvas,
+                    &mut state,
+                    mouse::Event::ButtonPressed(if cancellation == 7 {
+                        mouse::Button::Right
+                    } else {
+                        mouse::Button::Middle
+                    }),
+                    release,
+                );
+            }
+            9 => {
+                canvas::Program::update(
+                    &canvas,
+                    &mut state,
+                    &canvas::Event::Window(iced::window::Event::Unfocused),
+                    bounds(),
+                    mouse::Cursor::Available(release),
+                );
+            }
+            10 => {
+                input(
+                    &canvas,
+                    &mut state,
+                    mouse::Event::WheelScrolled {
+                        delta: mouse::ScrollDelta::Lines { x: 0., y: 1. },
+                    },
+                    release,
+                );
+            }
+            11 => {
+                input(&canvas, &mut state, mouse::Event::CursorLeft, release);
+            }
+            12 => {
+                motion(&canvas, &mut state, Point::new(-100., -100.), release);
+            }
+            13 => release_bounds.x += 25.,
+            15 => canvas.selected = f.b,
+            _ => {
+                let escape = canvas::Event::Keyboard(keyboard::Event::KeyPressed {
+                    key: keyboard::Key::Named(keyboard::key::Named::Escape),
+                    modified_key: keyboard::Key::Named(keyboard::key::Named::Escape),
+                    physical_key: keyboard::key::Physical::Code(keyboard::key::Code::Escape),
+                    location: keyboard::Location::Standard,
+                    modifiers: keyboard::Modifiers::empty(),
+                    text: None,
+                    repeat: false,
+                });
+                let event = canvas::Program::update(
+                    &canvas,
+                    &mut state,
+                    &escape,
+                    bounds(),
+                    mouse::Cursor::Available(release),
+                )
+                .and_then(|action| action.into_inner().0);
+                assert!(matches!(event, Some(Event::Choose(Tool::Select))));
+            }
+        }
+        let event = input_at_bounds(
+            &canvas,
+            &mut state,
+            mouse::Event::ButtonReleased(mouse::Button::Left),
+            release,
+            release_bounds,
+        );
+        assert!(
+            !matches!(event, Some(Event::SetBends { .. })),
+            "late release committed case {cancellation}"
+        );
+        assert!(
+            state.bend_preview.is_none(),
+            "stale preview survived case {cancellation}"
+        );
+        assert_eq!(f.project.diagrams[&f.diagram].routes[0], original);
+    }
+}
+
+#[test]
+fn state_bends_context_menu_distinguishes_authored_pin_from_computed_segment() {
+    let (f, relation) = bend_fixture(true);
+    let mut canvas = canvas(&f, Tool::Select, 1.);
+    canvas.selected = relation;
+    let mut state = State::default();
+    let scene = canvas.scene(&state).unwrap();
+    let pin = screen(&canvas, point(scene.routed.edges[&relation].pins[0]));
+    motion(&canvas, &mut state, pin, pin);
+    assert!(
+        matches!(input(&canvas, &mut state, mouse::Event::ButtonPressed(mouse::Button::Right), pin),
+        Some(Event::ContextMenu { context, object, placement: None, anchor, bend: Some(0), route_segment: None })
+        if context == canvas.context && object == relation && anchor == pin)
+    );
+    let (index, midpoint) = bend_segment(&scene, relation);
+    let at = screen(&canvas, midpoint);
+    motion(&canvas, &mut state, at, at);
+    assert!(
+        matches!(input(&canvas, &mut state, mouse::Event::ButtonPressed(mouse::Button::Right), at),
+        Some(Event::ContextMenu { context, object, placement: None, anchor, bend: None, route_segment: Some((segment, world)) })
+        if context == canvas.context && object == relation && anchor == at && segment == index && point(world).distance(midpoint) < 0.001)
+    );
+}
+
+#[test]
+fn state_bends_internal_rows_and_folded_proxies_cannot_acquire_pins() {
+    for internal in [false, true] {
+        let mut f = fixture();
+        let relation = if internal {
+            let id = f
+                .project
+                .relate(RelationKind::StateTransition, "Internal check", f.a, f.a);
+            if let RelationBody::StateTransition {
+                transition_kind, ..
+            } = &mut f.project.relations.get_mut(&id).unwrap().body
+            {
+                *transition_kind = TransitionKind::Internal;
+            }
+            id
+        } else {
+            let id = f.project.relate(
+                RelationKind::StateTransition,
+                "Hidden child to standby",
+                f.leaf,
+                f.b,
+            );
+            let parent = placement(&f, f.a);
+            f.project
+                .diagrams
+                .get_mut(&f.diagram)
+                .unwrap()
+                .nodes
+                .get_mut(&parent)
+                .unwrap()
+                .collapsed = true;
+            id
+        };
+        let mut canvas = canvas(&f, Tool::Select, 1.);
+        canvas.selected = relation;
+        let mut state = State::default();
+        let scene = canvas.scene(&state).unwrap();
+        let world = if internal {
+            assert!(!scene.routed.edges.contains_key(&relation));
+            let node = scene.view.nodes.iter().find(|n| n.element == f.a).unwrap();
+            internal_rows(&f.project, node)
+                .into_iter()
+                .find(|(r, _)| r.id == relation)
+                .unwrap()
+                .1
+                .center()
+        } else {
+            assert!(scene.routed.edges[&relation].custom_suspended);
+            bend_segment(&scene, relation).1
+        };
+        let start = screen(&canvas, world);
+        motion(&canvas, &mut state, start, start);
+        assert!(matches!(
+            input(
+                &canvas,
+                &mut state,
+                mouse::Event::ButtonPressed(mouse::Button::Right),
+                start
+            ),
+            Some(Event::ContextMenu {
+                bend: None,
+                route_segment: None,
+                ..
+            })
+        ));
+        bend_press(&canvas, &mut state, start);
+        let away = start + Vector::new(30., 20.);
+        motion(&canvas, &mut state, away, away);
+        assert!(state.bend_preview.is_none());
+        assert!(!matches!(
+            input(
+                &canvas,
+                &mut state,
+                mouse::Event::ButtonReleased(mouse::Button::Left),
+                away
+            ),
+            Some(Event::SetBends { .. })
+        ));
+        assert!(f.project.diagrams[&f.diagram].routes.is_empty());
+    }
+}
+
+#[test]
+fn state_bends_right_click_discards_provisional_indexes_before_building_menu() {
+    for click_pin in [true, false] {
+        let (mut f, relation) = bend_fixture(true);
+        let route = &mut f.project.diagrams.get_mut(&f.diagram).unwrap().routes[0];
+        route.waypoints = vec![Position { x: 650., y: 340. }, Position { x: 650., y: 390. }];
+        validate_candidate(&f.project).unwrap();
+        let original = f.project.diagrams[&f.diagram].routes[0].clone();
+        let mut canvas = canvas(&f, Tool::Select, 1.);
+        canvas.selected = relation;
+        let mut state = State::default();
+        let baseline = canvas.scene(&state).unwrap();
+        let edge = &baseline.routed.edges[&relation];
+        let candidates: Vec<_> = edge.points.windows(2).enumerate()
+            .filter(|(i, _)| *i > 0 && *i + 2 < edge.points.len())
+            .map(|(i, p)| (i, Point::new((p[0].x + p[1].x) / 2., (p[0].y + p[1].y) / 2.)))
+            .filter(|(_, p)| edge.pins.iter().all(|pin| p.distance(point(*pin)) > 20.))
+            .filter(|(_, p)| matches!(canvas.hit(&baseline, *p), Some(Hit::Transition(id)) if id == relation))
+            .filter(|(_, p)| !Rectangle::new(point(edge.label.bounds.position), Size::new(edge.label.bounds.size.width, edge.label.bounds.size.height)).contains(*p))
+            .collect();
+        let (_, insertion_at) = candidates
+            .iter()
+            .copied()
+            .find(|(i, p)| routing::pin_insertion_index(edge, *i, position(*p)) == 0)
+            .expect("exposed segment before both authored pins");
+        let menu_segment = candidates
+            .iter()
+            .copied()
+            .find(|(_, p)| p.distance(insertion_at) > 30.)
+            .expect("a distinct committed segment for the menu control");
+        let start = screen(&canvas, insertion_at);
+        bend_press(&canvas, &mut state, start);
+        let away = start + Vector::new(45., 30.);
+        motion(&canvas, &mut state, away, away);
+        let preview = state.bend_preview.as_ref().unwrap();
+        assert_eq!(preview.waypoints.len(), 3);
+        assert_eq!(
+            &preview.waypoints[1..],
+            original.waypoints.as_slice(),
+            "provisional insertion shifts both stored indices"
+        );
+
+        // With the left gesture still active, moving to the last stored pin also
+        // moves provisional pin0 there. The preview's first hit is therefore
+        // pin0, but a menu built after cancellation must identify stored pin1.
+        let menu_world = if click_pin {
+            point(original.waypoints[1])
+        } else {
+            menu_segment.1
+        };
+        let menu_window = screen(&canvas, menu_world);
+        motion(&canvas, &mut state, menu_window, menu_window);
+        assert!(state.bend_preview.is_some());
+        let menu = input(
+            &canvas,
+            &mut state,
+            mouse::Event::ButtonPressed(mouse::Button::Right),
+            menu_window,
+        )
+        .unwrap();
+        let Event::ContextMenu {
+            context,
+            object,
+            bend,
+            route_segment,
+            ..
+        } = menu
+        else {
+            panic!("expected context menu after cancelling drag")
+        };
+        assert_eq!(context, canvas.context);
+        assert_eq!(object, relation);
+        assert!(state.bend_preview.is_none());
+        assert_eq!(
+            canvas.scene(&state).unwrap().routed.edges[&relation].points,
+            edge.points
+        );
+        if click_pin {
+            assert_eq!(
+                bend,
+                Some(1),
+                "menu index must address the stored route, not the provisional route"
+            );
+            assert!(route_segment.is_none());
+            let remove = Event::RemoveBend {
+                context,
+                relation,
+                index: bend.unwrap(),
+            };
+            let plan = state_edit::plan(&f.project, context, &remove).unwrap();
+            let after = prepare_command(&f.project, &plan.command).unwrap().project;
+            let mut expected = f.project.clone();
+            expected.diagrams.get_mut(&f.diagram).unwrap().routes[0]
+                .waypoints
+                .remove(1);
+            assert_eq!(
+                after, expected,
+                "remove menu action must delete exactly the addressed original pin"
+            );
+        } else {
+            assert!(
+                bend.is_none(),
+                "provisional pin under cursor must not leak into menu"
+            );
+            let (segment, at) = route_segment.expect("committed route segment remains actionable");
+            assert_eq!(segment, menu_segment.0);
+            assert!(point(at).distance(menu_world) < 0.001);
+        }
+        assert!(
+            input(
+                &canvas,
+                &mut state,
+                mouse::Event::ButtonReleased(mouse::Button::Left),
+                menu_window
+            )
+            .is_none()
+        );
+        assert_eq!(f.project.diagrams[&f.diagram].routes[0], original);
+    }
+}
+
+#[test]
+fn state_bends_draw_before_update_excludes_preview_after_camera_or_bounds_change() {
+    for change in 0..4 {
+        let (f, relation) = bend_fixture(true);
+        let mut canvas = canvas(&f, Tool::Select, 1.);
+        canvas.selected = relation;
+        let mut state = State::default();
+        let baseline = canvas.scene_with_bounds(&state, Some(bounds())).unwrap();
+        let start = screen(&canvas, point(baseline.routed.edges[&relation].pins[0]));
+        let release = start + Vector::new(45., 30.);
+        bend_press(&canvas, &mut state, start);
+        motion(&canvas, &mut state, release, release);
+        let displayed_preview = canvas.scene_with_bounds(&state, Some(bounds())).unwrap();
+        assert_ne!(
+            displayed_preview.routed.edges[&relation].pins,
+            baseline.routed.edges[&relation].pins
+        );
+        let mut changed_bounds = bounds();
+        match change {
+            0 => canvas.zoom = 2.,
+            1 => canvas.pan.y += 25.,
+            2 => changed_bounds.x += 35.,
+            _ => changed_bounds.width -= 90.,
+        }
+        // No update event between camera/layout change and this draw-time read.
+        let shown = canvas
+            .scene_with_bounds(&state, Some(changed_bounds))
+            .unwrap();
+        assert_eq!(
+            shown.routed.edges[&relation].pins, baseline.routed.edges[&relation].pins,
+            "stale draw-time pins for case {change}"
+        );
+        assert_eq!(
+            shown.routed.edges[&relation].points, baseline.routed.edges[&relation].points,
+            "stale cached preview for case {change}"
+        );
+        let event = input_at_bounds(
+            &canvas,
+            &mut state,
+            mouse::Event::ButtonReleased(mouse::Button::Left),
+            release,
+            changed_bounds,
+        );
+        assert!(!matches!(event, Some(Event::SetBends { .. })));
+        assert!(state.bend_preview.is_none());
+    }
+}

crates/oa-desktop/src/behavior/state_canvas.rs

@@ -44,6 +44,8 @@ pub struct State {
     source: Option<Id>,
     preview: Option<(Id, Position)>,
     attachment_preview: Option<AttachmentPreview>,
+    bend: Option<BendGesture>,
+    bend_preview: Option<EdgeRoute>,
     pan_from: Option<(mouse::Button, Point)>,
     viewport: Option<Size>,
     attachment_viewport: Option<(f32, Vector, Rectangle)>,
@@ -84,6 +86,16 @@ enum Press {
         placement: Id,
         start: Point,
     },
+    Bend {
+        relation: Id,
+    },
+}
+
+struct BendGesture {
+    start: Point,
+    route: EdgeRoute,
+    index: usize,
+    baseline: Arc<Scene>,
 }
 
 #[derive(Clone, Copy, PartialEq)]
@@ -103,6 +115,7 @@ struct CachedScene {
     context: Context,
     preview: Option<(Id, Position)>,
     attachment_preview: Option<AttachmentPreview>,
+    bend_preview: Option<EdgeRoute>,
     scene: Arc<Scene>,
 }
 #[derive(PartialEq)]
@@ -110,6 +123,7 @@ struct PaintKey {
     context: Context,
     preview: Option<(Id, Position)>,
     attachment_preview: Option<AttachmentPreview>,
+    bend_preview: Option<EdgeRoute>,
     selected: Id,
     zoom: f32,
     pan: Vector,
@@ -122,11 +136,16 @@ enum Hit {
 }
 
 impl State {
-    fn cancel_gesture(&mut self) {
+    fn cancel_edit(&mut self) {
         self.press = None;
         self.preview = None;
         self.attachment_preview = None;
+        self.bend = None;
+        self.bend_preview = None;
         self.attachment_viewport = None;
+    }
+    fn cancel_gesture(&mut self) {
+        self.cancel_edit();
         self.pan_from = None;
     }
     fn reset(&mut self) {
@@ -669,25 +688,31 @@ impl StateCanvas<'_> {
             && state_edit::validate_context(self.project, self.context, self.context).is_ok()
     }
     fn scene(&self, state: &State) -> Option<Arc<Scene>> {
+        self.scene_with_bounds(state, None)
+    }
+    fn scene_with_bounds(&self, state: &State, bounds: Option<Rectangle>) -> Option<Arc<Scene>> {
         if !self.valid() {
             return None;
         }
+        let route_active = self.gesture_active(state) && self.route_viewport_current(state, bounds);
         let preview = self
             .gesture_active(state)
             .then_some(state.preview)
             .flatten();
-        let attachment_preview = self
-            .gesture_active(state)
-            .then_some(state.attachment_preview)
-            .flatten();
+        let attachment_preview = route_active.then_some(state.attachment_preview).flatten();
+        let bend_preview = route_active.then(|| state.bend_preview.clone()).flatten();
         if let Some(cached) = state.scene.borrow().as_ref()
             && cached.context == self.context
             && cached.preview == preview
             && cached.attachment_preview == attachment_preview
+            && cached.bend_preview == bend_preview
         {
             return Some(cached.scene.clone());
         }
         let mut diagram = self.project.diagrams.get(&self.diagram)?.clone();
+        if let Some(route) = &bend_preview {
+            crate::route_edit::with_route(&mut diagram, route.clone());
+        }
         if let Some(preview) = attachment_preview {
             let mut route = crate::route_edit::stored_route(&diagram, preview.relation);
             route.set_attachment(preview.end, Some(preview.attachment));
@@ -717,7 +742,17 @@ impl StateCanvas<'_> {
             }
         }
         let view = projection::project_diagram(self.project, &diagram);
-        let routed = routing::route_diagram(self.project, &diagram, &view);
+        let routed = if let Some(gesture) = state.bend.as_ref().filter(|_| bend_preview.is_some()) {
+            routing::route_edge_preview(
+                self.project,
+                &diagram,
+                &view,
+                &gesture.baseline.routed,
+                gesture.route.edge,
+            )
+        } else {
+            routing::route_diagram(self.project, &diagram, &view)
+        };
         let symbol_labels = symbol_labels(self.project, &view, &routed);
         let scene = Arc::new(Scene {
             view,
@@ -728,6 +763,7 @@ impl StateCanvas<'_> {
             context: self.context,
             preview,
             attachment_preview,
+            bend_preview,
             scene: scene.clone(),
         });
         Some(scene)
@@ -859,6 +895,84 @@ impl StateCanvas<'_> {
         .min_by(|a, b| a.1.total_cmp(&b.1))
         .map(|(endpoint, _)| (route.id, endpoint))
     }
+    fn bend_at(&self, scene: &Scene, world: Point) -> Option<usize> {
+        let edge = scene.routed.edges.get(&self.selected)?;
+        if edge.custom_suspended {
+            return None;
+        }
+        edge.pins
+            .iter()
+            .enumerate()
+            .filter_map(|(index, pin)| {
+                let distance = world.distance(point(*pin));
+                (distance <= 8. / self.scale()).then_some((index, distance))
+            })
+            .min_by(|a, b| a.1.total_cmp(&b.1).then(a.0.cmp(&b.0)))
+            .map(|(index, _)| index)
+    }
+    /// Preserve the rendered traversal index; overlapping runs can have the
+    /// same world point but different positions among the authored pins.
+    fn segment_at(&self, scene: &Scene, relation: Id, world: Point) -> Option<(usize, Position)> {
+        let edge = scene.routed.edges.get(&relation)?;
+        if edge.custom_suspended {
+            return None;
+        }
+        edge.points
+            .windows(2)
+            .enumerate()
+            .filter(|(index, _)| *index > 0 && index + 2 < edge.points.len())
+            .filter_map(|(index, span)| {
+                let projection = routing::project_onto_polyline(span, position(world))?;
+                (projection.distance <= 7. / self.scale()).then_some((index, projection.distance))
+            })
+            .min_by(|a, b| a.1.total_cmp(&b.1).then(a.0.cmp(&b.0)))
+            .map(|(index, _)| (index, position(world)))
+    }
+    fn begin_bend(
+        &self,
+        state: &mut State,
+        scene: Arc<Scene>,
+        window: Point,
+        route: EdgeRoute,
+        index: usize,
+        bounds: Rectangle,
+    ) {
+        state.press = Some(Press::Bend {
+            relation: route.edge,
+        });
+        state.attachment_viewport = Some((self.zoom, self.pan, bounds));
+        state.bend = Some(BendGesture {
+            start: window,
+            route,
+            index,
+            baseline: scene,
+        });
+        state.bend_preview = None;
+    }
+    fn move_bend_pointer(&self, state: &mut State, window: Point, local: Point) {
+        let Some(gesture) = &state.bend else {
+            return;
+        };
+        if window.distance(gesture.start) < 3. {
+            // Also discard a provisional insertion. The exact original route
+            // comes from the model, so an off-grid pin is never quantized here.
+            state.bend_preview = None;
+            return;
+        }
+        let world = self.world(local);
+        if !world.x.is_finite() || !world.y.is_finite() {
+            state.cancel_gesture();
+            return;
+        }
+        let mut changed = gesture.route.clone();
+        changed.waypoints[gesture.index] = Position {
+            x: (world.x / 5.).round() * 5.,
+            y: (world.y / 5.).round() * 5.,
+        };
+        let original =
+            crate::route_edit::stored_route(&self.project.diagrams[&self.diagram], changed.edge);
+        state.bend_preview = (changed != original).then_some(changed);
+    }
     fn owner_at(&self, scene: &Scene, world: Point, kind: Kind) -> Option<Id> {
         self.node_at(scene, world)
             .filter(|n| state_edit::eligible_owner(self.project, self.diagram, n.element, kind))
@@ -887,7 +1001,22 @@ impl StateCanvas<'_> {
         }
     }
     fn gesture_active(&self, state: &State) -> bool {
-        self.editable && state.context == Some(self.context) && state.tool == Some(self.tool)
+        self.editable
+            && state.context == Some(self.context)
+            && state.tool == Some(self.tool)
+            && state
+                .bend
+                .as_ref()
+                .is_none_or(|g| g.route.edge == self.selected)
+    }
+    fn route_viewport_current(&self, state: &State, bounds: Option<Rectangle>) -> bool {
+        state
+            .attachment_viewport
+            .is_none_or(|(zoom, pan, captured)| {
+                zoom == self.zoom
+                    && pan == self.pan
+                    && bounds.is_none_or(|current| current == captured)
+            })
     }
     fn move_attachment_pointer(&self, state: &mut State, window: Point, local: Point) {
         let Some(Press::Attachment {
@@ -941,6 +1070,23 @@ impl StateCanvas<'_> {
         if !self.editable {
             return "Pending edits · apply or cancel them before editing the diagram".into();
         }
+        if state.bend.is_some()
+            && self.gesture_active(state)
+            && self.route_viewport_current(state, None)
+        {
+            return "Move bend · release to keep · Esc cancels".into();
+        }
+        if self.tool == Tool::Select
+            && state.press.is_none()
+            && scene
+                .routed
+                .edges
+                .get(&self.selected)
+                .is_some_and(|edge| !edge.custom_suspended)
+        {
+            return "Drag line to add a bend · squares move bends · right-click a square to remove"
+                .into();
+        }
         if let Tool::AdjustAttachment { relation, end } = self.tool {
             return format!(
                 "Adjust {end:?} attachment of {} · drag that tip around its existing vertex boundary · Esc cancels · relation unchanged",
@@ -1035,11 +1181,18 @@ impl canvas::Program<Event> for StateCanvas<'_> {
             state.tool = Some(self.tool);
         }
         if !self.editable {
-            state.press = None;
-            state.preview = None;
-            state.attachment_preview = None;
+            // Pending edits block model changes, but read-only panning remains
+            // available and must survive successive pointer events.
+            state.cancel_edit();
             state.source = None;
         }
+        if state
+            .bend
+            .as_ref()
+            .is_some_and(|g| g.route.edge != self.selected)
+        {
+            state.cancel_gesture();
+        }
         if state
             .attachment_viewport
             .is_some_and(|view| view != (self.zoom, self.pan, bounds))
@@ -1055,6 +1208,9 @@ impl canvas::Program<Event> for StateCanvas<'_> {
             }
             canvas::Event::Mouse(mouse::Event::CursorLeft) => {
                 state.pointer = None;
+                if state.bend.is_some() {
+                    state.cancel_gesture();
+                }
                 cursor
             }
             canvas::Event::Mouse(
@@ -1150,10 +1306,23 @@ impl canvas::Program<Event> for StateCanvas<'_> {
                 }
                 if *button == mouse::Button::Right {
                     state.reset();
-                    let (object, placement) = match self.hit(&scene, world) {
-                        Some(Hit::Node { element, placement }) => (element, Some(placement)),
-                        Some(Hit::Transition(id) | Hit::StateAction(id)) => (id, None),
-                        None => (self.diagram, None),
+                    // A canceled provisional pin shifts indices in its preview.
+                    // Menu commands must target the committed route instead.
+                    let scene = self.scene(state)?;
+                    let bend = self.bend_at(&scene, world);
+                    let (object, placement) = if bend.is_some() {
+                        (self.selected, None)
+                    } else {
+                        match self.hit(&scene, world) {
+                            Some(Hit::Node { element, placement }) => (element, Some(placement)),
+                            Some(Hit::Transition(id) | Hit::StateAction(id)) => (id, None),
+                            None => (self.diagram, None),
+                        }
+                    };
+                    let route_segment = if bend.is_none() {
+                        self.segment_at(&scene, object, world)
+                    } else {
+                        None
                     };
                     return Some(
                         Action::publish(Event::ContextMenu {
@@ -1161,6 +1330,8 @@ impl canvas::Program<Event> for StateCanvas<'_> {
                             object,
                             placement,
                             anchor: window,
+                            bend,
+                            route_segment,
                         })
                         .and_capture(),
                     );
@@ -1178,6 +1349,14 @@ impl canvas::Program<Event> for StateCanvas<'_> {
                             });
                             return Some(Action::capture());
                         }
+                        if let Some(index) = self.bend_at(&scene, world) {
+                            let route = crate::route_edit::stored_route(
+                                &self.project.diagrams[&self.diagram],
+                                self.selected,
+                            );
+                            self.begin_bend(state, scene.clone(), window, route, index, bounds);
+                            return Some(Action::capture());
+                        }
                         match self.hit(&scene, world) {
                             Some(Hit::Node { placement, element }) => {
                                 let original = self
@@ -1198,6 +1377,36 @@ impl canvas::Program<Event> for StateCanvas<'_> {
                                 )
                             }
                             Some(Hit::Transition(id) | Hit::StateAction(id)) => {
+                                if id == self.selected
+                                    && let Some(edge) = scene.routed.edges.get(&id)
+                                    && !Rectangle::new(
+                                        point(edge.label.bounds.position),
+                                        Size::new(
+                                            edge.label.bounds.size.width,
+                                            edge.label.bounds.size.height,
+                                        ),
+                                    )
+                                    .contains(world)
+                                    && let Some((segment, at)) = self.segment_at(&scene, id, world)
+                                {
+                                    let mut route = crate::route_edit::stored_route(
+                                        &self.project.diagrams[&self.diagram],
+                                        id,
+                                    );
+                                    if let Some(index) = crate::route_edit::insert_pin_on_segment(
+                                        &mut route, edge, segment, at,
+                                    ) {
+                                        self.begin_bend(
+                                            state,
+                                            scene.clone(),
+                                            window,
+                                            route,
+                                            index,
+                                            bounds,
+                                        );
+                                        return Some(Action::capture());
+                                    }
+                                }
                                 Some(Action::publish(Event::Select(self.context, id)).and_capture())
                             }
                             None => {
@@ -1275,6 +1484,7 @@ impl canvas::Program<Event> for StateCanvas<'_> {
                 self.move_pointer(state, window);
                 if let Some(local) = local {
                     self.move_attachment_pointer(state, window, local);
+                    self.move_bend_pointer(state, window, local);
                 }
                 Some(Action::request_redraw())
             }
@@ -1298,14 +1508,24 @@ impl canvas::Program<Event> for StateCanvas<'_> {
                     self.move_pointer(state, window);
                     if let Some(local) = local {
                         self.move_attachment_pointer(state, window, local);
+                        self.move_bend_pointer(state, window, local);
                     }
                 }
                 let press = state.press.take()?;
                 state.attachment_viewport = None;
                 let preview = state.preview.take();
                 let attachment_preview = state.attachment_preview.take();
+                let bend_preview = state.bend_preview.take();
+                state.bend = None;
                 let world = local.map(|p| self.world(p));
                 let event = match press {
+                    Press::Bend { relation } if inside => bend_preview
+                        .filter(|route| route.edge == relation)
+                        .map(|route| Event::SetBends {
+                            context: self.context,
+                            relation,
+                            waypoints: route.waypoints,
+                        }),
                     Press::Move { node, .. } => preview.map(|(_, position)| Event::Move {
                         context: self.context,
                         node,
@@ -1416,19 +1636,19 @@ impl canvas::Program<Event> for StateCanvas<'_> {
         bounds: Rectangle,
         cursor: mouse::Cursor,
     ) -> Vec<canvas::Geometry> {
-        let Some(scene) = self.scene(state) else {
+        let Some(scene) = self.scene_with_bounds(state, Some(bounds)) else {
             return vec![];
         };
+        let route_active =
+            self.gesture_active(state) && self.route_viewport_current(state, Some(bounds));
         let key = PaintKey {
             context: self.context,
             preview: self
                 .gesture_active(state)
                 .then_some(state.preview)
                 .flatten(),
-            attachment_preview: self
-                .gesture_active(state)
-                .then_some(state.attachment_preview)
-                .flatten(),
+            attachment_preview: route_active.then_some(state.attachment_preview).flatten(),
+            bend_preview: route_active.then(|| state.bend_preview.clone()).flatten(),
             selected: self.selected,
             zoom: self.scale(),
             pan: self.pan,
@@ -1508,6 +1728,22 @@ impl canvas::Program<Event> for StateCanvas<'_> {
                         style::MUTED,
                     );
                     if active {
+                        if !edge.custom_suspended && self.tool == Tool::Select {
+                            for pin in &edge.pins {
+                                let radius = 4. / self.scale();
+                                let handle = Path::rectangle(
+                                    point(*pin) - Vector::new(radius, radius),
+                                    Size::new(radius * 2., radius * 2.),
+                                );
+                                frame.fill(&handle, Color::WHITE);
+                                frame.stroke(
+                                    &handle,
+                                    Stroke::default()
+                                        .with_color(style::TEAL)
+                                        .with_width(1.6 / self.scale()),
+                                );
+                            }
+                        }
                         for end in [edge.points.first(), edge.points.last()]
                             .into_iter()
                             .flatten()
@@ -1922,6 +2158,8 @@ mod tests {
     use super::*;
     use crate::document::Document;
 
+    include!("state_bend_tests.rs");
+
     struct Fixture {
         project: Project,
         diagram: Id,
@@ -2377,7 +2615,7 @@ mod tests {
         motion(&canvas, &mut state, at, at);
         assert!(matches!(input(&canvas, &mut state,
             mouse::Event::ButtonPressed(mouse::Button::Right), at),
-            Some(Event::ContextMenu { context, object, placement: Some(node), anchor })
+            Some(Event::ContextMenu { context, object, placement: Some(node), anchor, .. })
             if context == canvas.context && object == f.b
                 && node == placement(&f, f.b) && anchor == at));
         let background = Point::new(
@@ -2387,7 +2625,7 @@ mod tests {
         motion(&canvas, &mut state, background, background);
         assert!(matches!(input(&canvas, &mut state,
             mouse::Event::ButtonPressed(mouse::Button::Right), background),
-            Some(Event::ContextMenu { context, object, placement: None, anchor })
+            Some(Event::ContextMenu { context, object, placement: None, anchor, .. })
             if context == canvas.context && object == f.diagram && anchor == background));
     }
 

crates/oa-desktop/src/behavior/state_edit.rs

@@ -39,6 +39,8 @@ pub enum Event {
         object: Id,
         placement: Option<Id>,
         anchor: iced::Point,
+        bend: Option<usize>,
+        route_segment: Option<(usize, Position)>,
     },
     CreateAt {
         context: Context,
@@ -74,6 +76,25 @@ pub enum Event {
         placement: Id,
         attachment: Option<EdgeAttachment>,
     },
+    SetBends {
+        context: Context,
+        relation: Id,
+        waypoints: Vec<Position>,
+    },
+    AddBend {
+        context: Context,
+        relation: Id,
+        segment: Option<(usize, Position)>,
+    },
+    RemoveBend {
+        context: Context,
+        relation: Id,
+        index: usize,
+    },
+    ClearBends {
+        context: Context,
+        relation: Id,
+    },
 }
 
 impl Event {
@@ -93,7 +114,11 @@ impl Event {
             | Self::Move { context: c, .. }
             | Self::Connect { context: c, .. }
             | Self::Reconnect { context: c, .. }
-            | Self::SetAttachment { context: c, .. } => Some(*c),
+            | Self::SetAttachment { context: c, .. }
+            | Self::SetBends { context: c, .. }
+            | Self::AddBend { context: c, .. }
+            | Self::RemoveBend { context: c, .. }
+            | Self::ClearBends { context: c, .. } => Some(*c),
         }
     }
 }
@@ -288,6 +313,24 @@ pub fn attachment_node(
     view.nodes.iter().find(|node| node.id == owner).cloned()
 }
 
+/// Actual visible State transition geometry, never an internal row or folded proxy.
+pub fn bend_route(
+    project: &Project,
+    diagram: Id,
+    relation: Id,
+) -> Option<oa_core::routing::RoutedEdge> {
+    machine(project, diagram).ok()?;
+    if project.relations.get(&relation)?.kind() != RelationKind::StateTransition {
+        return None;
+    }
+    let stored = project.diagrams.get(&diagram)?;
+    let view = projection::project_diagram(project, stored);
+    let geometry = oa_core::routing::route_diagram(project, stored, &view)
+        .edges
+        .remove(&relation)?;
+    (!geometry.custom_suspended).then_some(geometry)
+}
+
 fn checked(project: &Project, plan: Plan) -> Result<Plan, ModelError> {
     prepare_command(project, &plan.command)?;
     Ok(plan)
@@ -547,6 +590,66 @@ pub fn plan(project: &Project, current: Context, event: &Event) -> Result<Plan,
             route.set_attachment(end, attachment);
             (Command::SetEdgeRoute { diagram, route }, relation, None)
         }
+        Event::SetBends { relation, .. }
+        | Event::AddBend { relation, .. }
+        | Event::RemoveBend { relation, .. }
+        | Event::ClearBends { relation, .. } => {
+            let geometry = bend_route(project, diagram, relation)
+                .ok_or_else(|| error("Choose an actual visible transition route in this view."))?;
+            let mut route = crate::route_edit::stored_route(&project.diagrams[&diagram], relation);
+            match event {
+                Event::SetBends { waypoints, .. } => {
+                    if waypoints.len() > 128 {
+                        return Err(error("A route supports at most 128 bends."));
+                    }
+                    for &point in waypoints {
+                        finite(point)?;
+                    }
+                    route.waypoints = waypoints.clone();
+                }
+                Event::AddBend { segment, .. } => {
+                    let (segment, point) = segment
+                        .or_else(|| {
+                            geometry
+                                .points
+                                .windows(2)
+                                .enumerate()
+                                .filter(|(index, _)| {
+                                    *index > 0 && index + 2 < geometry.points.len()
+                                })
+                                .max_by(|(_, a), (_, b)| {
+                                    let length = |s: &[Position]| {
+                                        (s[1].x - s[0].x).abs() + (s[1].y - s[0].y).abs()
+                                    };
+                                    length(a).total_cmp(&length(b))
+                                })
+                                .map(|(index, span)| {
+                                    (
+                                        index,
+                                        Position {
+                                            x: (span[0].x + span[1].x) / 2.,
+                                            y: (span[0].y + span[1].y) / 2.,
+                                        },
+                                    )
+                                })
+                        })
+                        .ok_or_else(|| error("This route has no interior segment for a bend."))?;
+                    crate::route_edit::insert_pin_on_segment(&mut route, &geometry, segment, point)
+                        .ok_or_else(|| {
+                            error("The bend segment is stale, invalid, or at capacity.")
+                        })?;
+                }
+                Event::RemoveBend { index, .. } => {
+                    if *index >= route.waypoints.len() {
+                        return Err(error("This bend no longer exists."));
+                    }
+                    route.waypoints.remove(*index);
+                }
+                Event::ClearBends { .. } => route.waypoints.clear(),
+                _ => unreachable!(),
+            }
+            (Command::SetEdgeRoute { diagram, route }, relation, None)
+        }
         _ => {
             return Err(error(
                 "Handle this navigation or tool request without a model command.",

crates/oa-desktop/src/behavior/state_menu.rs

@@ -161,6 +161,53 @@ pub fn popup(app: &App, opened: &Opened, clean: bool) -> Option<Menu<Message>> {
             );
             entries.push(item("Edit transition", edit, true));
             if let Some(context) = context {
+                let bend_geometry = state_edit::bend_route(project, context.diagram, id);
+                let bend_count = bend_geometry.as_ref().map_or(0, |route| route.pins.len());
+                let can_add = bend_geometry.as_ref().is_some_and(|route| {
+                    bend_count < 128
+                        && request.route_segment.map_or_else(
+                            || route.points.len() >= 4,
+                            |(index, point)| {
+                                index
+                                    .checked_add(2)
+                                    .is_some_and(|end| end <= route.points.len())
+                                    && point.x.is_finite()
+                                    && point.y.is_finite()
+                            },
+                        )
+                });
+                entries.push(item(
+                    if request.route_segment.is_some() {
+                        "Add bend here"
+                    } else {
+                        "Add bend"
+                    },
+                    diagram_event(Event::AddBend {
+                        context,
+                        relation: id,
+                        segment: request.route_segment,
+                    }),
+                    can_add,
+                ));
+                if let Some(index) = request.bend {
+                    entries.push(item(
+                        "Remove bend",
+                        diagram_event(Event::RemoveBend {
+                            context,
+                            relation: id,
+                            index,
+                        }),
+                        bend_geometry.is_some() && index < bend_count,
+                    ));
+                }
+                entries.push(item(
+                    "Clear bends",
+                    diagram_event(Event::ClearBends {
+                        context,
+                        relation: id,
+                    }),
+                    bend_geometry.is_some() && bend_count > 0,
+                ));
                 let visible = projection::project_view(project, context.diagram)
                     .edges
                     .iter()

crates/oa-desktop/src/guide.rs

@@ -307,7 +307,7 @@ fn article(topic: Topic) -> Article {
                             "Choose and edit the relationship you mean",
                             &[
                                 "Use the diagram selector or + View to work with a focused diagram. View properties edits its name, perspective, projection and Saved view visibility. Apply changes commits the view settings.",
-                                "Choose Containment for semantic children, Architecture · allocated work for responsibilities, Functional dataflow for work and exchanges, or Missions & capabilities for outcomes. All relationships is a broader exploration view; OA ↔ SA traceability displays counterparts.",
+                                "Choose Containment for semantic children, Architecture · allocated work for responsibilities, Functional dataflow for work and exchanges, or Missions & capabilities for outcomes. All relationships explores one layer; OA ↔ SA traceability can show placed elements from both layers and their correspondence lines alongside ordinary relationships.",
                                 "Select an element and edit Semantic parent to change ownership. Use an Allocation relationship to change responsibility. Apply changes validates the semantic change.",
                                 "Scroll to zoom and use Fit to frame the current view. In allocated-work views, dragging work changes its assignment and placement together. Choose Arrange next drag or press Alt+A to move work without changing responsibility for that one drag; Escape cancels the armed action. Auto-layout arranges the whole view. Export SVG produces a shareable view.",
                                 "Select a diagram node to access Placement, Fold / unfold and Hide. With the canvas focused, Delete hides its placement; Shift+Delete asks to remove the model element. Other views retain a hidden element. Undo restores either change.",
@@ -317,6 +317,16 @@ fn article(topic: Topic) -> Article {
                             "Keep diagrams readable",
                             "Use separate views for responsibility, decomposition and cross-layer coverage. Place existing elements with Show in this diagram. A placement's Diagram field can relocate it while preserving its identity and artifact references. Do not duplicate a semantic element merely to show it in another view.",
                         ),
+                        walkthrough(
+                            "Show a correspondence between OA and SA",
+                            &[
+                                "Choose OA ↔ SA traceability in View content. Changing this setting does not create counterparts or add their placements, so an existing single-layer diagram can initially look unchanged.",
+                                "Use Review layer traces to inspect named Operational and System endpoints and the meaning of their link. This opens the model's layer-trace list with no search restriction; traces between relationships are reviewed here rather than drawn between element cards.",
+                                "In the chosen architecture view, use Add existing elements. The chooser offers compatible elements from both layers. Select an existing endpoint and click its position in the canvas; repeat for the other end if needed. This adds a placement, not a new semantic element or trace. For port correspondences, place the ports' owners.",
+                                "The view shows correspondence lines alongside ordinary relationships. The shown-line count reflects the current projection and visibility settings, not trace coverage. If a line is hidden, use View visibility and inspect Saved view visibility; placing an endpoint does not remove explicit hides or filters.",
+                                "If the counterpart is already placed, use Include already shown (Locate) in the chooser. Undo restores an added placement; saving preserves each view's placements independently. Use the Traceability page's existing counterpart or manual-trace workflow when the semantic link itself does not yet exist.",
+                            ],
+                        ),
                         walkthrough(
                             "Move work between performers",
                             &[
@@ -565,6 +575,7 @@ fn article(topic: Topic) -> Article {
                                 "Choose + Region and click the highlighted machine, or a State/Mode for a nested region. Choose Initial, State, Mode or another kind from + State / symbol, then click its highlighted owning region. Rename the new element in Properties.",
                                 "Choose Transition and drag from a source vertex to a compatible target, or click the source and then the target. In Select / move, drag states or containers to arrange them; a container moves its descendant placements without changing ownership.",
                                 "Select a drawn transition and drag its endpoint handle to reconnect it. Its right-click menu also offers Reconnect source and Reconnect target; choose one, then click a compatible vertex. To change only where a line touches its existing vertex, choose Adjust source attachment or Adjust target attachment, then drag the highlighted tip along the boundary. Reset source attachment or Reset target attachment restores automatic placement for that end without changing the transition's meaning or other route settings. Escape cancels an attachment drag.",
+                                "To shape a selected transition, drag an exposed line segment to add a bend, or drag a square bend handle to move it. Right-click a square and choose Remove bend. The transition's Actions menu also offers Add bend and Clear bends; clearing bends keeps its attachment points and label placement. Bends belong to this saved view. A click alone changes nothing, Escape cancels a drag, and Undo restores the complete edit. Internal transition rows and folded connections do not expose bend editing while their route is hidden.",
                                 "Right-click a state or the background for New transition with details… to create Local, Internal or timed behavior. Right-click an existing transition and choose Edit transition to edit its kind, triggers, guard and effects. EntryPoint outgoing transitions use Local. Apply accepts the complete form; invalid drafts remain available for correction.",
                             ],
                         ),

crates/oa-desktop/src/model_menu.rs

@@ -14,6 +14,7 @@ pub struct Request {
     pub placement: Option<Id>,
     pub bend: Option<usize>,
     pub route_point: Option<Position>,
+    pub route_segment: Option<(usize, Position)>,
     pub creation_point: Option<Position>,
     pub canvas: Option<route_edit::Context>,
     pub source_file: Option<String>,
@@ -26,6 +27,7 @@ impl Request {
             placement: None,
             bend: None,
             route_point: None,
+            route_segment: None,
             creation_point: None,
             canvas: None,
             source_file: None,
@@ -456,7 +458,8 @@ pub fn popup(app: &App) -> Option<Menu<Message>> {
                 entries.push(item(
                     "Show in this diagram",
                     Message::PlaceSelected,
-                    d.layer == e.layer() && d.projection.includes(e.kind()),
+                    (d.layer == e.layer() || d.projection == ProjectionKind::Traceability)
+                        && d.projection.includes(e.kind()),
                 ));
             }
         }
@@ -587,6 +590,7 @@ fn relation_actions(kind: Kind) -> &'static [(&'static str, RelationKind, bool)]
 #[cfg(test)]
 mod tests {
     use super::*;
+    include!("model_menu_traceability_tests.rs");
     fn send(app: &mut App, message: Message) {
         let _ = app.update(message);
     }

crates/oa-desktop/src/model_menu_traceability_tests.rs

@@ -0,0 +1,62 @@
+#[test]
+fn traceability_show_menu_matches_cross_layer_and_port_placement_eligibility() {
+    let mut project = Project::empty();
+    let sa = project
+        .add_element(Kind::Function, Layer::Sa, "Counterpart", None)
+        .unwrap();
+    let port = Id::new_v4();
+    project.elements.insert(
+        port,
+        Element {
+            id: port,
+            alias: "legacy_port".into(),
+            name: "Port".into(),
+            description: String::new(),
+            parent: Some(sa),
+            body: ElementBody::shared_in(
+                Layer::Sa,
+                SharedBody::Port {
+                    contract: PortContract::Legacy,
+                    legacy: Some(LegacyPortContract {
+                        direction: PortDirection::InOut,
+                        interface: None,
+                    }),
+                },
+            ),
+        },
+    );
+    let diagram = project.ensure_diagram(Layer::Oa);
+    oa_core::validate_candidate(&project).unwrap();
+    for projection in [ProjectionKind::Overview, ProjectionKind::Traceability] {
+        let mut p = project.clone();
+        p.diagrams.get_mut(&diagram).unwrap().projection = projection;
+        let mut app = App::with_project(p);
+        app.page = Page::Diagram;
+        app.layer = Layer::Oa;
+        app.active_diagram = Some(diagram);
+        for object in [sa, port] {
+            send(&mut app, open(object, Point::ORIGIN));
+            let action = popup(&app)
+                .unwrap()
+                .entries
+                .into_iter()
+                .find_map(|e| match e {
+                    Entry::Action { label, message, .. } if label == "Show in this diagram" => {
+                        Some(message)
+                    }
+                    _ => None,
+                });
+            if object == port {
+                assert!(
+                    action.is_none(),
+                    "Ports never acquire independent node placements"
+                );
+            } else {
+                assert_eq!(
+                    action.expect("non-port placement entry").is_some(),
+                    projection == ProjectionKind::Traceability
+                );
+            }
+        }
+    }
+}

crates/oa-desktop/src/route_edit.rs

@@ -137,6 +137,34 @@ pub fn stored_route(diagram: &Diagram, edge: Id) -> EdgeRoute {
 }
 
 /// Insert after the pins preceding the clicked segment along the routed path.
+pub fn insert_pin_on_segment(
+    route: &mut EdgeRoute,
+    geometry: &RoutedEdge,
+    segment: usize,
+    point: Position,
+) -> Option<usize> {
+    if route.edge != geometry.id
+        || geometry.custom_suspended
+        || route.waypoints != geometry.pins
+        || route.waypoints.len() >= 128
+        || !point.x.is_finite()
+        || !point.y.is_finite()
+        || geometry
+            .points
+            .get(segment..segment.checked_add(2)?)
+            .is_none()
+    {
+        return None;
+    }
+    let index = pin_insertion_index(geometry, segment, point);
+    if index > route.waypoints.len() {
+        return None;
+    }
+    route.waypoints.insert(index, point);
+    Some(index)
+}
+
+/// Find a segment when an ordinary caller has only a point, not a captured hit.
 pub fn insert_pin(route: &mut EdgeRoute, geometry: &RoutedEdge, point: Position) -> usize {
     let segment = geometry
         .points

crates/oa-desktop/src/views.rs

@@ -599,6 +599,28 @@ fn diagram(app: &App) -> View<'_, Message> {
     }
     if let Some(diagram) = app.active_diagram {
         let view = oa_core::projection::project_view(app.project(), diagram);
+        if projection == Some(ProjectionKind::Traceability) {
+            let correspondence_lines = view.edges.iter().filter(|edge| edge.trace).count();
+            tools = tools.push(
+                column![
+                    label("Shows OA and SA elements together, with correspondence lines alongside ordinary relationships."),
+                    label("Place both ends of a trace to show its line. Port traces use their owner cards; traces between relationships are reviewed on the Traceability page."),
+                    row![
+                        label(format!("{correspondence_lines} correspondence lines in this view")),
+                        action(
+                            "Add existing elements…",
+                            Message::Architecture(crate::app::architecture_authoring::Event::Existing(None))
+                        ),
+                        action("Review layer traces", Message::ReviewLayerTraces),
+                        action("View visibility…", Message::Select(diagram)),
+                    ]
+                    .spacing(7)
+                    .align_y(iced::Center)
+                    .wrap(),
+                ]
+                .spacing(4),
+            );
+        }
         let edge = view.edges.iter().find(|edge| edge.id == app.selected);
         let promoted = edge.is_some_and(|edge| {
             oa_core::projection::edge_endpoint_placements(

harness/state-bends-20260923.md

@@ -0,0 +1,90 @@
+# State transition bend editing — issue 23
+
+Branch-specific work above attachment source `53d01a3`, on
+`codex/state-bends-ytr83r-20260923`.
+[Issue 23](http://217.177.34.108:3000/sorokin.oleg.edu/ARCADIA-Studio/issues/23)
+owns live scope and acceptance. This document records the design; it does not
+assert completed verification or integration.
+
+The user asks to edit bends in State-machine connections as in architecture
+diagrams. State already renders `EdgeRoute.waypoints`; its missing capability is
+interactive authoring. Bends are positions in one saved diagram. They neither
+change transition endpoints/meaning nor belong to every view of the transition.
+
+## Interaction decision
+
+Use direct manipulation of an already selected transition: drag an exposed line
+segment to insert one bend, or drag an authored square handle to move that bend.
+An initial selection click changes no route. Endpoint circles retain semantic
+reconnect behavior; the separate attachment action retains its explicit mode.
+State vertices and action rows retain selection/movement precedence. Clicking
+a transition label selects it; this task does not introduce label dragging.
+
+The transition menu offers Add bend here when invoked on an eligible segment,
+or Add bend at the longest interior segment from Actions. Right-clicking an
+authored square offers Remove bend. Clear bends removes all authored waypoints
+in this view while retaining both attachment preferences and the label override.
+Existing transition Delete behavior stays explicit and separate; this design
+does not add a pin-specific Delete shortcut.
+
+Alternatives considered: an Edit bends mode makes the distinction visible but
+adds another persistent tool and cancellation/focus state; menu-only editing is
+discoverable but too slow for repeated shaping. Direct dragging plus explicit
+menu actions matches the existing architecture workflow without another mode.
+The menu provides a recovery path when a label or endpoint covers a line hit.
+
+## Invariants
+
+- Only an actual visible, unsuspended routed State transition can be edited.
+  Internal transitions render as rows rather than lines. Folded endpoint proxies
+  suspend authored routing. In both cases existing dormant waypoints survive;
+  the UI disables operations instead of deleting metadata.
+- Generated elbows, mandatory endpoint leads and computed self-loop detours are
+  routing output, not authored bends. Editing inserts one pin, never the entire
+  computed polyline. The picked rendered-segment index determines insertion
+  among stored pins, including reversed or overlapping traversals.
+- Movement requires three screen pixels. Dragged pins snap to the existing
+  five-unit grid. A stationary press or return within three screen pixels
+  restores the exact baseline, including imported off-grid coordinates and
+  absence of a stored route. It creates no history entry.
+- Preview uses the actual routing engine and captured baseline. The model stays
+  unchanged until release. A successful drag replaces only `waypoints` in the
+  current route, leaving attachments, label, relation metadata and other views
+  exact, in one existing `SetEdgeRoute` transaction.
+- A gesture belongs to its document, diagram, revision, interaction epoch,
+  selected transition and viewport. Escape, pending edits, tool/context changes,
+  camera/bounds changes, focus loss, pointer exit, outside release and a pan/menu
+  interruption cancel it. A canceled preview must not supply menu pin indices.
+  A delayed drag result must not apply after selecting another object.
+- Finite positions, valid indices and the existing 128-pin limit are checked at
+  the command boundary. Exact no-ops are suppressed before execution.
+
+## Verification plan
+
+Use real canvas event tests at multiple zooms for insertion/movement, ordered
+cursor input, cancellation, exact return-to-press, preview invalidation and menu
+targets. Planner/app tests compare entire Projects and source bundles across
+Undo/Redo, preserve attachments/label/reference views, and refuse internal,
+folded, nonfinite, stale, pending and capacity-invalid operations. Exercise
+right-click during a provisional insertion and selection changes before queued
+commit admission. Retain existing attachment/reconnect and focused Delete tests.
+
+Then exercise the actual Windows application: add, move, remove and clear bends;
+check unchanged attachments and independent views; Save/Undo/Redo and reopen;
+observe menus, guidance, preview and normal close. Bind evidence to an identified
+source/binary and predeclared complete-Project expectations. Compilation alone
+does not establish interaction acceptance. Linux remains user-paused.
+
+The first full workspace run exposed a read-only pan regression: canceling model
+edits on every pending-draft event also canceled the middle-button pan. Keep
+edit cancellation separate from navigation cancellation; the existing scoped
+pan regression exercises this distinction. The self-loop test also distinguishes
+typed-model restoration by Clear from byte-exact source restoration by Undo:
+source-preserving edits may retain harmless empty-list whitespace, whereas Undo
+must recover the original source bundle exactly. Failed run receipts are retained;
+these findings do not assert that the corrected candidate has passed its gates.
+
+Codex-956atf retains issue 16 resize and issue 27 integration ownership. This
+work uses the existing State model/router and needs composition with those
+contributions. It does not certify a combined release, change Process/Scenario
+notation, redesign automatic arrangement or adopt a new routing schema.

harness/traceability-view-20260923.md

@@ -0,0 +1,73 @@
+# Traceability view comprehension — issue 31
+
+Branch-specific work above `b8685416f56e53e30bd11ecf93a54cea10ac8458`.
+[Issue31](http://217.177.34.108:3000/sorokin.oleg.edu/ARCADIA-Studio/issues/31)
+owns live progress. This note records the chosen design and acceptance plan,
+not completed validation or integration.
+
+The user's observed problem is that OA↔SA traceability looks like All
+relationships and its purpose is unclear. Existing core behavior already
+projects both layers' placed elements, ordinary relationships and explicit
+traces with available endpoints. Switching projection neither creates semantic
+counterparts nor adds missing placements. Existing Add existing supports both
+layers, but its default suggested-type filter conceals opposite-layer choices.
+Show in this diagram also has inconsistent cross-layer eligibility and selects
+an opposite-layer element before placement, potentially changing the target view.
+
+## Decision and criteria
+
+Make the existing workflow understandable and reachable before introducing a
+second counterpart browser. Criteria: a new user can explain the distinction,
+find both named ends, place existing counterparts in the chosen saved diagram,
+see/inspect correspondence, understand absent lines, and preserve semantic data.
+Keep the established mixed ordinary/trace contract, explicit semantic creation,
+saved view filters and single-operation placement history.
+
+Use concise projection-local explanation, the actual count of projected trace
+edges, Add existing elements, Review layer traces, and existing View visibility.
+Default the Existing chooser to All compatible types only for Traceability;
+creation and ordinary-view defaults stay scoped to their existing contexts.
+Align Show in this diagram with actual supported placement and retain the
+captured diagram across cross-layer selection. Review layer traces opens a
+predictable layer-trace inventory without a stale artifact filter/search, through
+existing navigation/draft guards. It does not promise that subsequently choosing
+an opposite-layer endpoint preserves the originating diagram.
+
+The count is exactly `project_view(...).edges.filter(trace).count()`, after saved
+filters. It is neither a project-wide trace total nor a coverage denominator.
+No overlapping missing/hidden reasons are added into invented totals. Port
+correspondences use owner-card placements; relation-to-relation correspondences
+remain reviewable semantic records and are not promised a diagram line.
+
+An expandable view-local counterpart browser with named Place/Locate actions
+was independently proposed. It can reduce name memorization, but introduces
+another scope, owner-mapping, omission-reason and targeted-placement interface.
+The existing chooser already completes the bounded placement task once its
+default and shortcut are corrected. Revisit the richer browser if the actual
+native task remains confusing. Tooltip-only, traces-only replacement, automatic
+counterpart creation/placement and forced OA/SA layout were rejected: respectively
+weak task completion, broken mixed-context contract, surprising semantics/history,
+and unwanted authored-layout changes.
+
+## Verification plan
+
+Exercise the real Existing chooser and actual Show menu path for opposite-layer
+elements, including stale/pending refusal and ordinary-view restrictions. Only
+the current diagram's intended placement may change; preserve semantic maps,
+other views, route/visibility choices, exact source Undo/Redo and save/reopen.
+Ports cannot become node placements. An already placed element must not acquire
+a duplicate placement. Predictable trace review must preserve drafts and obey
+the usual modal/navigation guards.
+
+Use core projection/filter evidence for no trace, missing endpoints, both placed,
+ordinary OA/SA edges, multiple traces, explicit hides plus disabled Trace kind,
+port owners and relation correspondence. Do not infer visible lines from
+unfiltered edge_availability or confuse unrelated model traces with counterparts.
+
+Native acceptance starts with an OA-owned mixed view, one already visible
+correspondence pair and another existing named SA counterpart not yet placed.
+Find/place it through the visible controls, see/select the additional trace,
+inspect an absent-line visibility reason, Undo/Redo and Save/reopen. Inspect
+toolbar/canvas space and chooser clarity at a realistic window size. Different
+help text or count tests alone do not resolve the user's comprehension complaint.
+Linux remains user-paused; Codex-956atf retains shared integration ownership.