test(application): document user-not-found silent-skip and locality guard in FederationEventService

crates/application/src/services/federation_event.rs

@@ -28,6 +28,8 @@ impl FederationEventService {
             }
 
             DomainEvent::ThoughtDeleted { thought_id, user_id } => {
+                // No DB lookup — thought is already deleted when this event fires.
+                // No locality guard: delete commands only reach local thoughts via the use case.
                 let ap_id = format!("{}/thoughts/{}", self.base_url, thought_id);
                 self.ap.broadcast_delete(user_id, &ap_id).await
             }
@@ -215,6 +217,7 @@ mod tests {
             .unwrap();
 
         assert_eq!(spy.updated.lock().unwrap().len(), 1);
+        assert_eq!(spy.updated.lock().unwrap()[0], thought.id);
     }
 
     #[tokio::test]
@@ -278,4 +281,45 @@ mod tests {
         assert!(spy.updated.lock().unwrap().is_empty());
         assert!(spy.announced.lock().unwrap().is_empty());
     }
+
+    #[tokio::test]
+    async fn thought_created_does_not_broadcast_if_user_missing() {
+        let store = TestStore::default();
+        let alice = alice();
+        let thought = local_thought(alice.id.clone());
+        // Don't push alice into users — simulates user deleted before handler runs
+        store.thoughts.lock().unwrap().push(thought.clone());
+
+        let spy = Arc::new(SpyPort::default());
+        svc(&store, spy.clone())
+            .process(&DomainEvent::ThoughtCreated {
+                thought_id: thought.id.clone(),
+                user_id: alice.id.clone(),
+                in_reply_to_id: None,
+            })
+            .await
+            .unwrap();
+
+        assert!(spy.created.lock().unwrap().is_empty());
+    }
+
+    #[tokio::test]
+    async fn thought_updated_does_not_broadcast_if_user_missing() {
+        let store = TestStore::default();
+        let alice = alice();
+        let thought = local_thought(alice.id.clone());
+        // Don't push alice into users
+        store.thoughts.lock().unwrap().push(thought.clone());
+
+        let spy = Arc::new(SpyPort::default());
+        svc(&store, spy.clone())
+            .process(&DomainEvent::ThoughtUpdated {
+                thought_id: thought.id.clone(),
+                user_id: alice.id.clone(),
+            })
+            .await
+            .unwrap();
+
+        assert!(spy.updated.lock().unwrap().is_empty());
+    }
 }