fix(cmux-tui): fence repeated ABA echo keys

cmux-tui/crates/cmux-tui-core/src/mux.rs

@@ -6526,6 +6526,13 @@ impl Mux {
         source: AgentSource,
         session: Option<&str>,
     ) -> anyhow::Result<Option<String>> {
+        // Resource revisions are durable and strictly monotonic. Include the
+        // current revision in the transition key so an ABA sequence cannot
+        // reuse the key from an earlier cycle after the compatibility cache
+        // returns to the same state. Repeated polls of one semantic state
+        // still return early through `unchanged`, so steady-state reports do
+        // not append another echo.
+        let resource_revision = self.state.lock().unwrap().resource_revision;
         // The durable projection is updated before its echo is folded. Read
         // it first so a blocked roster replay still has a stable semantic
         // receipt for repeated reports.
@@ -6619,7 +6626,7 @@ impl Mux {
         // journal cursor would make an unrelated event defeat coalescing and
         // turn a steady socket poll into one durable row per event elsewhere.
         let material = format!(
-            "agent-report-echo-v4|{terminal_id}|{}|{}|{:?}|{previous}",
+            "agent-report-echo-v5|{terminal_id}|{}|{}|{:?}|revision={resource_revision}|{previous}",
             state.as_str(),
             source.as_str(),
             session,
@@ -24711,6 +24718,65 @@ mod tests {
         std::fs::remove_dir_all(root).unwrap();
     }
 
+    #[test]
+    fn socket_echoes_do_not_reuse_keys_after_repeated_aba_cycles() {
+        let root = std::env::temp_dir().join(format!(
+            "cmux-roster-aba-repeat-echo-{}",
+            crate::workspace_registry::new_uuid_v4()
+        ));
+        let mux = Mux::open_persistent("roster-aba-repeat-echo", SurfaceOptions::default(), &root)
+            .unwrap();
+        let surface = mux.new_workspace(None, None).unwrap();
+        let terminal_id = surface.terminal_public_id().cloned().expect("workspace terminal");
+        let states = [
+            AgentState::Working,
+            AgentState::Blocked,
+            AgentState::Working,
+            AgentState::Blocked,
+            AgentState::Working,
+            AgentState::Blocked,
+        ];
+
+        for state in states {
+            mux.report_agent(
+                surface.id,
+                state,
+                AgentSource::Socket,
+                Some("aba-repeat-session".into()),
+            )
+            .unwrap();
+        }
+
+        let keys =
+            mux.workspace_registry
+                .lock()
+                .unwrap()
+                .session_journal_after(0, 1024)
+                .unwrap()
+                .records
+                .into_iter()
+                .filter(|record| {
+                    record.subjects.iter().any(|subject| {
+                        subject.kind == "terminal" && subject.id == terminal_id.as_str()
+                    })
+                })
+                .filter_map(|record| {
+                    (record
+                        .payload
+                        .get("adapter")
+                        .and_then(|adapter| adapter.get("id"))
+                        .and_then(Value::as_str)
+                        == Some(crate::journal_reducers::SOCKET_REPORT_ADAPTER))
+                    .then_some(record.event_id)
+                })
+                .collect::<std::collections::HashSet<_>>();
+        assert_eq!(keys.len(), states.len(), "each ABA transition needs a unique echo");
+
+        mux.shutdown();
+        drop(mux);
+        std::fs::remove_dir_all(root).unwrap();
+    }
+
     #[test]
     fn repeated_socket_done_reports_coalesce_after_roster_removal() {
         let root = std::env::temp_dir()