diff --git a/crates/oa-core/src/ports.rs b/crates/oa-core/src/ports.rs
index 463c9af4..7d066784 100644
--- a/crates/oa-core/src/ports.rs
+++ b/crates/oa-core/src/ports.rs
@@ -251,6 +251,20 @@ pub(crate) fn functional_exchange_commands(
 ) -> Result<Vec<Command>, ModelError> {
     vacant(p, request.id)?;
     let mut working = p.clone();
+    let mut relation = Relation {
+        id: request.id,
+        alias: request.alias.clone(),
+        name: request.name.clone(),
+        description: request.description.clone(),
+        body: RelationBody::new(
+            RelationKind::FunctionalExchange,
+            request.source,
+            request.target,
+        ),
+    };
+    // Reserve the authored alias as well as identity before naming generated
+    // endpoints. This draft exists only in the planner's private candidate.
+    working.relations.insert(relation.id, relation.clone());
     let mut commands = Vec::new();
     let label = if request.name.trim().is_empty() {
         "Exchange"
@@ -289,19 +303,14 @@ pub(crate) fn functional_exchange_commands(
         &request.items,
         &mut commands,
     )?;
-    commands.push(Command::CreateRelation(Relation {
-        id: request.id,
-        alias: request.alias.clone(),
-        name: request.name.clone(),
-        description: request.description.clone(),
-        body: RelationBody::FunctionalExchange {
-            source: request.source,
-            target: request.target,
-            source_port,
-            target_port,
-            items: request.items.clone(),
-        },
-    }));
+    relation.body = RelationBody::FunctionalExchange {
+        source: request.source,
+        target: request.target,
+        source_port,
+        target_port,
+        items: request.items.clone(),
+    };
+    commands.push(Command::CreateRelation(relation));
     Ok(commands)
 }
 fn add_allocation(
@@ -392,6 +401,14 @@ pub fn plan_component_exchange(
             target_port,
         } => {
             vacant(&working, *id)?;
+            let mut relation = Relation {
+                id: *id,
+                alias: alias.clone(),
+                name: name.clone(),
+                description: description.clone(),
+                body: RelationBody::new(RelationKind::BoundaryExchange, Id::nil(), Id::nil()),
+            };
+            working.relations.insert(*id, relation.clone());
             let contract = |outgoing| PortContract::Component {
                 kind: *port_kind,
                 orientation: if *port_kind == ComponentPortKind::Standard {
@@ -424,17 +441,11 @@ pub fn plan_component_exchange(
                 contract(false),
             )?;
             let b = select_port(&mut working, *target_port, input_port, items, &mut commands)?;
-            let relation = Relation {
-                id: *id,
-                alias: alias.clone(),
-                name: name.clone(),
-                description: description.clone(),
-                body: RelationBody::BoundaryExchange {
-                    source: a,
-                    target: b,
-                    oriented: *oriented,
-                    items: items.clone(),
-                },
+            relation.body = RelationBody::BoundaryExchange {
+                source: a,
+                target: b,
+                oriented: *oriented,
+                items: items.clone(),
             };
             working.relations.insert(*id, relation.clone());
             commands.push(Command::CreateRelation(relation));
@@ -646,6 +657,66 @@ pub fn plan_function_port_items(
     finish(p, vec![Command::EditElement(port, e)])
 }
 
+/// Whether removing these allocation facts breaks a typed exchange mapping.
+/// Legacy or malformed endpoints are left to their own validation rules; this
+/// helper only determines the conditional dependency on PortAllocation facts.
+pub(crate) fn missing_exchange_port_allocations(
+    p: &Project,
+    relation: &Relation,
+    removed: &BTreeSet<Id>,
+) -> bool {
+    let Some(Relation {
+        body:
+            RelationBody::BoundaryExchange {
+                source: a,
+                target: b,
+                oriented,
+                ..
+            },
+        ..
+    }) = p.relations.get(&relation.source())
+    else {
+        return false;
+    };
+    let Some(Relation {
+        body:
+            RelationBody::FunctionalExchange {
+                source_port,
+                target_port,
+                ..
+            },
+        ..
+    }) = p.relations.get(&relation.target())
+    else {
+        return false;
+    };
+    if ![*a, *b].iter().all(|id| {
+        p.elements
+            .get(id)
+            .is_some_and(|e| matches!(port_contract(e), Some(PortContract::Component { .. })))
+    }) || !p
+        .elements
+        .get(source_port)
+        .is_some_and(|e| matches!(port_contract(e), Some(PortContract::FunctionOutput { .. })))
+        || !p
+            .elements
+            .get(target_port)
+            .is_some_and(|e| matches!(port_contract(e), Some(PortContract::FunctionInput { .. })))
+    {
+        return false;
+    }
+    let allocated = |component, function| {
+        p.relations.values().any(|allocation| {
+            allocation.kind() == RelationKind::PortAllocation
+                && !removed.contains(&allocation.id)
+                && allocation.source() == component
+                && allocation.target() == function
+        })
+    };
+    !((allocated(*a, *source_port) && allocated(*b, *target_port))
+        || (!*oriented && allocated(*b, *source_port) && allocated(*a, *target_port)))
+}
+
 pub(crate) fn validate_port(p: &Project, e: &Element, out: &mut Vec<Issue>) {
     let Some(SharedBody::Port { contract, legacy }) = e.shared() else {
         return;
diff --git a/crates/oa-core/src/references.rs b/crates/oa-core/src/references.rs
index 16b7f230..20f740f2 100644
--- a/crates/oa-core/src/references.rs
+++ b/crates/oa-core/src/references.rs
@@ -203,6 +203,9 @@ pub fn remap_references(p: &mut Project, old: Id, new: Id) {
 }
 /// IDs removed by a cascade. Cross-layer traced counterparts are never included.
 pub fn deletion_impact(p: &Project, id: Id) -> BTreeSet<Id> {
+    deletion_impact_inner(p, id, false)
+}
+fn deletion_impact_inner(p: &Project, id: Id, defer_exchange_allocations: bool) -> BTreeSet<Id> {
     let mut removed = BTreeSet::from([id]);
     loop {
         let before = removed.len();
@@ -254,12 +257,15 @@ pub fn deletion_impact(p: &Project, id: Id) -> BTreeSet<Id> {
             else {
                 continue;
             };
-            if p.relations.values().any(|allocation| {
-                allocation.kind() == RelationKind::PortAllocation
-                    && removed.contains(&allocation.id)
-                    && [boundary.source(), boundary.target()].contains(&allocation.source())
-                    && [*source_port, *target_port].contains(&allocation.target())
-            }) {
+            if !defer_exchange_allocations
+                && p.relations.values().any(|allocation| {
+                    allocation.kind() == RelationKind::PortAllocation
+                        && removed.contains(&allocation.id)
+                        && [boundary.source(), boundary.target()].contains(&allocation.source())
+                        && [*source_port, *target_port].contains(&allocation.target())
+                })
+                && crate::ports::missing_exchange_port_allocations(p, r, &removed)
+            {
                 removed.insert(r.id);
             }
         }
@@ -288,6 +294,40 @@ pub fn deletion_impact(p: &Project, id: Id) -> BTreeSet<Id> {
 }
 pub fn delete_cascade(p: &mut Project, id: Id) {
     let removed = deletion_impact(p, id);
+    remove_objects(p, removed);
+}
+/// Preserve conditional exchange-allocation dependents until the transaction
+/// has had the opportunity to supply explicit replacement allocation facts.
+pub(crate) fn delete_cascade_deferred(p: &mut Project, id: Id, pending: &mut BTreeSet<Id>) {
+    let complete = deletion_impact(p, id);
+    let removed = deletion_impact_inner(p, id, true);
+    // An explicitly removed relation cannot pass its conditional cascade on
+    // to a new relation that later reuses the same identity in this batch.
+    pending.retain(|id| !removed.contains(id));
+    pending.extend(
+        complete
+            .difference(&removed)
+            .filter(|id| {
+                p.relations
+                    .get(id)
+                    .is_some_and(|r| r.kind() == RelationKind::ExchangeAllocation)
+            })
+            .copied(),
+    );
+    remove_objects(p, removed);
+}
+pub(crate) fn finish_deletions(p: &mut Project, pending: &BTreeSet<Id>) {
+    let none = BTreeSet::new();
+    for id in pending {
+        if p.relations.get(id).is_some_and(|r| {
+            r.kind() == RelationKind::ExchangeAllocation
+                && crate::ports::missing_exchange_port_allocations(p, r, &none)
+        }) {
+            delete_cascade(p, *id);
+        }
+    }
+}
+fn remove_objects(p: &mut Project, removed: BTreeSet<Id>) {
     let removed_names: std::collections::BTreeMap<_, _> = removed
         .iter()
         .map(|id| (*id, p.named(*id).to_string()))
diff --git a/crates/oa-core/src/session.rs b/crates/oa-core/src/session.rs
index 8dadaee9..4ff59dbb 100644
--- a/crates/oa-core/src/session.rs
+++ b/crates/oa-core/src/session.rs
@@ -1,5 +1,6 @@
 use crate::*;
 use serde::{Deserialize, Serialize};
+use std::collections::BTreeSet;
 use thiserror::Error;
 
 #[derive(Debug, Clone, Error, Serialize, Deserialize)]
@@ -135,7 +136,9 @@ impl Session {
     }
     pub fn execute(&mut self, command: Command) -> Result<Option<Id>, ModelError> {
         let mut candidate = self.project.clone();
-        let selected = apply_command(&mut candidate, &command, 0)?;
+        let mut pending_deletions = BTreeSet::new();
+        let selected = apply_command(&mut candidate, &command, 0, &mut pending_deletions)?;
+        crate::references::finish_deletions(&mut candidate, &pending_deletions);
         validate_candidate(&candidate)?;
         if candidate != self.project {
             self.past
@@ -161,9 +164,11 @@ pub fn validate_candidate(p: &Project) -> Result<(), ModelError> {
 }
 pub fn execute_batch(project: &Project, commands: &[Command]) -> Result<Project, ModelError> {
     let mut candidate = project.clone();
+    let mut pending_deletions = BTreeSet::new();
     for command in commands {
-        apply_command(&mut candidate, command, 0)?;
+        apply_command(&mut candidate, command, 0, &mut pending_deletions)?;
     }
+    crate::references::finish_deletions(&mut candidate, &pending_deletions);
     validate_candidate(&candidate)?;
     Ok(candidate)
 }
@@ -224,7 +229,12 @@ fn attach(p: &mut Project, id: Id) {
         }
     }
 }
-fn apply_command(p: &mut Project, c: &Command, depth: usize) -> Result<Option<Id>, ModelError> {
+fn apply_command(
+    p: &mut Project,
+    c: &Command,
+    depth: usize,
+    pending_deletions: &mut BTreeSet<Id>,
+) -> Result<Option<Id>, ModelError> {
     if depth > 64 {
         return Err(ModelError(
             "Command batch nesting exceeds 64 levels.".into(),
@@ -233,12 +243,13 @@ fn apply_command(p: &mut Project, c: &Command, depth: usize) -> Result<Option<Id
     let selected = match c {
         Command::Replace(value) => {
             *p = value.clone();
+            pending_deletions.clear();
             None
         }
         Command::Batch(commands) => {
             let mut selected = None;
             for command in commands {
-                let id = apply_command(p, command, depth + 1)?;
+                let id = apply_command(p, command, depth + 1, pending_deletions)?;
                 if id.is_some() {
                     selected = id;
                 }
@@ -318,6 +329,9 @@ fn apply_command(p: &mut Project, c: &Command, depth: usize) -> Result<Option<Id
             v.id = *old;
             p.relations.insert(*old, v);
             reidentify(p, *old, value.id)?;
+            if pending_deletions.remove(old) {
+                pending_deletions.insert(value.id);
+            }
             Some(value.id)
         }
         Command::CreateDiagram(value) => {
@@ -438,6 +452,9 @@ fn apply_command(p: &mut Project, c: &Command, depth: usize) -> Result<Option<Id
         }
         Command::Reidentify(old, new) => {
             reidentify(p, *old, *new)?;
+            if pending_deletions.remove(old) {
+                pending_deletions.insert(*new);
+            }
             Some(*new)
         }
         Command::Rename(id, value) => {
@@ -469,7 +486,7 @@ fn apply_command(p: &mut Project, c: &Command, depth: usize) -> Result<Option<Id
                         items: vec![],
                     },
                 )?;
-                return apply_command(p, &Command::Batch(commands), depth + 1);
+                return apply_command(p, &Command::Batch(commands), depth + 1, pending_deletions);
             }
             Some(p.relate(*kind, name, *source, *target))
         }
@@ -480,7 +497,7 @@ fn apply_command(p: &mut Project, c: &Command, depth: usize) -> Result<Option<Id
             if !p.contains(*id) {
                 return Err(missing());
             }
-            crate::references::delete_cascade(p, *id);
+            crate::references::delete_cascade_deferred(p, *id, pending_deletions);
             None
         }
         Command::AddStep(owner, exchange) => {
@@ -519,7 +536,7 @@ fn apply_command(p: &mut Project, c: &Command, depth: usize) -> Result<Option<Id
                 .and_then(Element::steps)
                 .and_then(|s| s.get(*index))
                 .ok_or_else(|| ModelError("Step index is out of range.".into()))?;
-            crate::references::delete_cascade(p, id);
+            crate::references::delete_cascade_deferred(p, id, pending_deletions);
             Some(*owner)
         }
         Command::MoveStep(owner, from, to) => {
diff --git a/crates/oa-core/tests/release_ports.rs b/crates/oa-core/tests/release_ports.rs
index 30b3a6e9..3b952d82 100644
--- a/crates/oa-core/tests/release_ports.rs
+++ b/crates/oa-core/tests/release_ports.rs
@@ -137,6 +137,245 @@ fn ambiguous_reuse_creates_a_fresh_port_and_collisions_never_overwrite() {
     assert_eq!(p.elements[&other], occupied);
 }
 
+#[test]
+fn generated_ports_respect_authored_exchange_aliases() {
+    let mut p = Project::empty();
+    let a = add(&mut p, Kind::Function, Layer::Sa, "Send");
+    let b = add(&mut p, Kind::Function, Layer::Sa, "Receive");
+    for alias in ["message_output", "message_input"] {
+        let mut req = request(&p, a, b, vec![]);
+        req.alias = alias.into();
+        req.source_port = PortChoice::Create;
+        req.target_port = PortChoice::Create;
+        let commands = plan_functional_exchange(&p, &req).unwrap();
+        assert_eq!(
+            serde_json::to_value(&commands).unwrap(),
+            serde_json::to_value(plan_functional_exchange(&p, &req).unwrap()).unwrap()
+        );
+        let result = execute_batch(&p, &commands).unwrap();
+        assert_eq!(result.relations[&req.id].alias, alias);
+        let (output, input) = endpoints(&result, req.id);
+        assert_eq!(output, Id::new_v5(&req.id, b"function-source-port"));
+        assert_eq!(input, Id::new_v5(&req.id, b"function-target-port"));
+        assert_ne!(result.elements[&output].alias, alias);
+        assert_ne!(result.elements[&input].alias, alias);
+        assert!(!p.contains(req.id));
+        req.alias = p.elements[&a].alias.clone();
+        assert!(plan_functional_exchange(&p, &req).is_err());
+    }
+
+    let (mut p, a, b, _, fe) = fixture();
+    allocate(&mut p, a, b);
+    for alias in ["boundary_source_port", "boundary_target_port"] {
+        let mut req = component_request(&p, fe, ComponentPortKind::Flow);
+        let id = boundary_id(&req);
+        if let ComponentExchangeChoice::Create {
+            alias: authored,
+            source_port,
+            target_port,
+            ..
+        } = &mut req.boundary
+        {
+            *authored = alias.into();
+            *source_port = PortChoice::Create;
+            *target_port = PortChoice::Create;
+        }
+        let commands = plan_component_exchange(&p, &req).unwrap();
+        assert_eq!(
+            serde_json::to_value(&commands).unwrap(),
+            serde_json::to_value(plan_component_exchange(&p, &req).unwrap()).unwrap()
+        );
+        let result = execute_batch(&p, &commands).unwrap();
+        assert_eq!(result.relations[&id].alias, alias);
+        let (source, target) = result.relations[&id].body.endpoints();
+        assert_ne!(result.elements[&source].alias, alias);
+        assert_ne!(result.elements[&target].alias, alias);
+        assert!(!p.contains(id));
+        if let ComponentExchangeChoice::Create { alias, .. } = &mut req.boundary {
+            *alias = p.elements[&a].alias.clone();
+        }
+        assert!(plan_component_exchange(&p, &req).is_err());
+    }
+}
+
+fn allocated_fixture() -> (Project, Id, Id, Id) {
+    let (mut p, a, b, _, fe) = fixture();
+    allocate(&mut p, a, b);
+    let req = component_request(&p, fe, ComponentPortKind::Flow);
+    p = execute_batch(&p, &plan_component_exchange(&p, &req).unwrap()).unwrap();
+    let allocation = p
+        .relations
+        .values()
+        .find(|r| r.kind() == RelationKind::PortAllocation)
+        .unwrap()
+        .id;
+    let exchange_allocation = p
+        .relations
+        .values()
+        .find(|r| r.kind() == RelationKind::ExchangeAllocation)
+        .unwrap()
+        .id;
+    p.relations
+        .get_mut(&exchange_allocation)
+        .unwrap()
+        .description = "Retain this authored mapping rationale".into();
+    let artifact = Id::new_v4();
+    p.artifact_links.insert(
+        artifact,
+        ArtifactLink {
+            id: artifact,
+            alias: "mapping_evidence".into(),
+            name: "Allocation evidence".into(),
+            description: "Keep the original evidence".into(),
+            owner: exchange_allocation,
+            relation: ArtifactRelation::References,
+            uri: "docs/port-rationale.md".into(),
+            revision: Some("r1".into()),
+            fragment: None,
+        },
+    );
+    validate_candidate(&p).unwrap();
+    (p, allocation, exchange_allocation, artifact)
+}
+
+#[test]
+fn replacement_port_allocation_retains_exchange_mapping_and_evidence_in_either_order() {
+    let (p, old, exchange_allocation, artifact) = allocated_fixture();
+    let mut replacement = p.relations[&old].clone();
+    replacement.id = Id::new_v4();
+    replacement.alias = "replacement_mapping".into();
+    for delete_first in [false, true] {
+        let mut commands = vec![
+            Command::CreateRelation(replacement.clone()),
+            Command::Delete(old),
+        ];
+        if delete_first {
+            commands.reverse();
+        }
+        let mut expected = p.clone();
+        expected.relations.remove(&old);
+        expected
+            .relations
+            .insert(replacement.id, replacement.clone());
+        let mut session = Session::new(p.clone());
+        session.execute(Command::Batch(commands)).unwrap();
+        assert_eq!(session.project(), &expected);
+        assert_eq!(
+            session.project().relations[&exchange_allocation],
+            p.relations[&exchange_allocation]
+        );
+        assert_eq!(
+            session.project().artifact_links[&artifact],
+            p.artifact_links[&artifact]
+        );
+        assert_eq!(session.revision(), 1);
+        session.undo();
+        assert_eq!(session.project(), &p);
+        assert!(!session.can_undo());
+    }
+}
+
+#[test]
+fn deferred_deletion_preserves_preview_explicit_deletion_and_reidentification() {
+    let (p, old, exchange_allocation, artifact) = allocated_fixture();
+    let impact = references::deletion_impact(&p, old);
+    assert!(impact.contains(&exchange_allocation));
+    assert!(impact.contains(&artifact));
+    let result = execute_batch(&p, &[Command::Delete(old)]).unwrap();
+    assert!(impact.iter().all(|id| !result.contains(*id)));
+    let mut expected = p.clone();
+    references::delete_cascade(&mut expected, old);
+    assert_eq!(result, expected);
+
+    let mut replacement = p.relations[&old].clone();
+    replacement.id = Id::new_v4();
+    replacement.alias = "replacement_mapping".into();
+    let explicit = execute_batch(
+        &p,
+        &[
+            Command::Delete(old),
+            Command::Delete(exchange_allocation),
+            Command::CreateRelation(replacement.clone()),
+        ],
+    )
+    .unwrap();
+    assert!(!explicit.contains(exchange_allocation));
+    assert!(!explicit.contains(artifact));
+    assert_eq!(explicit.relations[&replacement.id], replacement);
+
+    let renamed = Id::new_v4();
+    let mut edited = p.relations[&exchange_allocation].clone();
+    edited.id = renamed;
+    for command in [
+        Command::Reidentify(exchange_allocation, renamed),
+        Command::EditRelation(exchange_allocation, edited),
+    ] {
+        let result = execute_batch(&p, &[Command::Delete(old), command.clone()]).unwrap();
+        assert_eq!(result, expected);
+        let preserved = execute_batch(
+            &p,
+            &[
+                Command::Delete(old),
+                command,
+                Command::CreateRelation(replacement.clone()),
+            ],
+        )
+        .unwrap();
+        assert_eq!(
+            preserved.relations[&renamed].description,
+            p.relations[&exchange_allocation].description
+        );
+        assert_eq!(preserved.artifact_links[&artifact].owner, renamed);
+    }
+
+    let recreated = execute_batch(
+        &p,
+        &[
+            Command::Delete(old),
+            Command::Delete(exchange_allocation),
+            Command::CreateRelation(replacement),
+            Command::CreateRelation(p.relations[&exchange_allocation].clone()),
+        ],
+    )
+    .unwrap();
+    assert_eq!(
+        recreated.relations[&exchange_allocation],
+        p.relations[&exchange_allocation]
+    );
+    assert!(!recreated.contains(artifact));
+}
+
+#[test]
+fn invalid_replacement_rolls_back_without_repairing_explicit_replacement_projects() {
+    let (p, old, exchange_allocation, _) = allocated_fixture();
+    let mut replacement = p.relations[&old].clone();
+    replacement.id = Id::new_v4();
+    replacement.alias = "invalid_replacement_mapping".into();
+    // The reverse allocation is an invalid role, even if deletion would remove
+    // its dependent exchange allocation before the final candidate check.
+    replacement.body = RelationBody::PortAllocation {
+        source: replacement.target(),
+        target: replacement.source(),
+    };
+    let mut invalid_project = p.clone();
+    invalid_project.relations.remove(&old);
+    for commands in [
+        vec![Command::Delete(old), Command::CreateRelation(replacement)],
+        vec![Command::Delete(old), Command::Replace(invalid_project)],
+        vec![
+            Command::Delete(old),
+            Command::Delete(exchange_allocation),
+            Command::CreateRelation(p.relations[&exchange_allocation].clone()),
+        ],
+    ] {
+        let mut session = Session::new(p.clone());
+        assert!(session.execute(Command::Batch(commands)).is_err());
+        assert_eq!(session.project(), &p);
+        assert_eq!(session.revision(), 0);
+        assert!(!session.can_undo());
+    }
+}
+
 #[test]
 fn component_generation_requires_real_allocations_and_reuses_existing_facts() {
     let (mut p, a, b, _, fe) = fixture();