diff --git a/codex-rs/tui/src/app.rs b/codex-rs/tui/src/app.rs
index 258944b15c..82bba8241d 100644
--- a/codex-rs/tui/src/app.rs
+++ b/codex-rs/tui/src/app.rs
@@ -215,6 +215,7 @@ mod app_server_events;
 pub(crate) mod app_server_requests;
 mod app_server_thread_ownership;
 mod backend_banner_fallback;
+mod backend_events;
 mod background_requests;
 mod composer_hints;
 mod config_panel;
diff --git a/codex-rs/tui/src/app/agents_overview_tests.rs b/codex-rs/tui/src/app/agents_overview_tests.rs
index 8603973f3e..1293fe6533 100644
--- a/codex-rs/tui/src/app/agents_overview_tests.rs
+++ b/codex-rs/tui/src/app/agents_overview_tests.rs
@@ -573,9 +573,9 @@ async fn shared_overview_seeds_once_and_retains_locally_resumed_history() -> Res
     tokio::time::timeout(Duration::from_secs(10), async {
         loop {
             let event = app_server.next_event().await.expect("server notification");
-            let is_created = matches!(&event, AppServerEvent::ServerNotification(notification)
+            let is_created = matches!(&event.event, AppServerEvent::ServerNotification(notification)
                 if matches!(notification.as_ref(), ServerNotification::ThreadStarted(started) if started.thread.id == created.to_string()));
-            app.handle_app_server_event(&app_server, event).await;
+            app.handle_backend_event(&app_server, event).await;
             if is_created { break; }
         }
     }).await.expect("creation notification received");
diff --git a/codex-rs/tui/src/app/backend_events.rs b/codex-rs/tui/src/app/backend_events.rs
new file mode 100644
index 0000000000..8fc839c5c9
--- /dev/null
+++ b/codex-rs/tui/src/app/backend_events.rs
@@ -0,0 +1,19 @@
+//! Checks incoming event ownership before consulting native-thread caches or UI state.
+
+use super::App;
+use crate::app_server_session::AppServerSession;
+use crate::app_server_session::AppServerSessionEvent;
+
+impl App {
+    pub(super) async fn handle_backend_event(
+        &mut self,
+        app_server: &AppServerSession,
+        event: AppServerSessionEvent,
+    ) {
+        if event.backend_id != app_server.backend_id() {
+            tracing::warn!("ignoring server event from a different backend");
+            return;
+        }
+        self.handle_app_server_event(app_server, event.event).await;
+    }
+}
diff --git a/codex-rs/tui/src/app/event_dispatch.rs b/codex-rs/tui/src/app/event_dispatch.rs
index 81b7718dfa..89bdf72a00 100644
--- a/codex-rs/tui/src/app/event_dispatch.rs
+++ b/codex-rs/tui/src/app/event_dispatch.rs
@@ -814,13 +814,13 @@ impl App {
                 // transcript would hide the fact that server history has already changed.
                 tokio::time::timeout(Duration::from_secs(/*secs*/ 10), async {
                     while let Some(event) = app_server.next_event().await {
-                        let is_reverted = matches!(
-                            &event,
+                        let is_reverted = event.backend_id == app_server.backend_id() && matches!(
+                            &event.event,
                             AppServerEvent::ServerNotification(notification)
                                 if matches!(notification.as_ref(), ServerNotification::ThreadReverted(notification)
                                     if notification.thread_id == thread_id.to_string())
                         );
-                        self.handle_app_server_event(app_server, event).await;
+                        self.handle_backend_event(app_server, event).await;
                         if is_reverted {
                             return Ok(());
                         }
diff --git a/codex-rs/tui/src/app/startup.rs b/codex-rs/tui/src/app/startup.rs
index 787e7b947b..143653936f 100644
--- a/codex-rs/tui/src/app/startup.rs
+++ b/codex-rs/tui/src/app/startup.rs
@@ -1383,7 +1383,7 @@ See the Codex keymap documentation for supported actions and examples."
                     app_server_event = app_server.next_event(), if listen_for_app_server_events && !app.reconnect.offline
                         && (matches!(app.app_server_target, AppServerTarget::Embedded) || !has_pending_app_events) => {
                         match app_server_event {
-                            Some(event) => app.handle_app_server_event(&app_server, event).await,
+                            Some(event) => app.handle_backend_event(&app_server, event).await,
                             None => {
                                 listen_for_app_server_events = false;
                                 app.begin_reconnect();
diff --git a/codex-rs/tui/src/app/tests.rs b/codex-rs/tui/src/app/tests.rs
index fd09c4091c..2e03905e1c 100644
--- a/codex-rs/tui/src/app/tests.rs
+++ b/codex-rs/tui/src/app/tests.rs
@@ -483,7 +483,8 @@ async fn next_thread_settings_updated(
         .await
         .expect("app-server should emit an event")
         .expect("app-server event stream should remain open");
-        if let codex_app_server_client::AppServerEvent::ServerNotification(notification) = event
+        if let codex_app_server_client::AppServerEvent::ServerNotification(notification) =
+            event.event
             && let ServerNotification::ThreadSettingsUpdated(notification) = *notification
             && notification.thread_id == thread_id.to_string()
         {
@@ -2876,7 +2877,7 @@ fn selected_and_resumed_threads_use_server_capability_for_v1_and_v2_children() -
             app_server.thread_unsubscribe(child_thread_id).await?;
             let closed = tokio::time::timeout(Duration::from_secs(/*secs*/ 5), async {
                 while let Some(event) = app_server.next_event().await {
-                    if matches!(&event,
+                    if matches!(&event.event,
                         codex_app_server_client::AppServerEvent::ServerNotification(notification)
                             if matches!(notification.as_ref(), ServerNotification::ThreadClosed(closed)
                                 if closed.thread_id == child_thread_id.to_string()))
@@ -2891,7 +2892,7 @@ fn selected_and_resumed_threads_use_server_capability_for_v1_and_v2_children() -
             app.select_agent_thread(&mut tui, &mut app_server, child_thread_id)
                 .await?;
             // A queued close from the old runtime must not undo the new attachment.
-            app.handle_app_server_event(&app_server, closed).await;
+            app.handle_backend_event(&app_server, closed).await;
             app.drain_active_thread_events(&mut tui).await?;
             assert_eq!(app.active_thread_id, Some(child_thread_id));
             assert!(!matches!(
@@ -3188,7 +3189,8 @@ async fn handle_start_side_seeds_navigation_before_thread_started() -> Result<()
         .await
         .expect("app-server should emit an event")
         .expect("app-server event stream should remain open");
-        if let codex_app_server_client::AppServerEvent::ServerNotification(notification) = event
+        if let codex_app_server_client::AppServerEvent::ServerNotification(notification) =
+            event.event
             && let ServerNotification::ThreadStarted(notification) = notification.as_ref()
             && notification.thread.id == side_thread_id.to_string()
         {
@@ -10267,3 +10269,6 @@ mod active_reconnect;
 #[cfg(unix)]
 #[path = "tests/navigation_reconnect_tests.rs"]
 mod navigation_reconnect;
+
+#[path = "tests/backend_event_tests.rs"]
+mod backend_event_tests;
diff --git a/codex-rs/tui/src/app/tests/backend_event_tests.rs b/codex-rs/tui/src/app/tests/backend_event_tests.rs
new file mode 100644
index 0000000000..dfb93688d2
--- /dev/null
+++ b/codex-rs/tui/src/app/tests/backend_event_tests.rs
@@ -0,0 +1,105 @@
+//! Incoming events cannot use a colliding native thread ID to mutate another backend's state.
+
+use super::*;
+use crate::app_server_session::AppServerSessionEvent;
+use crate::backend_id::BackendId;
+use codex_app_server_client::AppServerEvent;
+use pretty_assertions::assert_eq;
+
+#[tokio::test]
+async fn foreign_backend_events_leave_thread_cache_and_connection_untouched() -> Result<()> {
+    let (mut app, mut events, _) = make_test_app_with_channels().await;
+    let (server, requests, proxy) =
+        session_lifecycle_requests::start_recording_remote_app_server(&app.config).await?;
+    let id = ThreadId::new();
+    app.primary_thread_id = Some(id);
+    app.active_thread_id = Some(id);
+    set_test_initial_prompt(&mut app, String::new());
+    app.chat_widget
+        .handle_thread_session(test_thread_session(id, app.config.cwd.to_path_buf()));
+    app.chat_widget
+        .restore_user_message_to_composer("keep draft".into());
+    app.ensure_thread_channel(id);
+    while events.try_recv().is_ok() {}
+    requests.lock().unwrap().clear();
+    let input = app.chat_widget.capture_thread_input_state();
+    let foreign = BackendId::new();
+    let request = exec_approval_request(id, "foreign-turn", "command", /*approval_id*/ None);
+    for event in [
+        AppServerEvent::ServerNotification(Box::new(turn_started_notification(id, "foreign-turn"))),
+        AppServerEvent::ServerRequest(Box::new(request.clone())),
+        AppServerEvent::Lagged { skipped: 1 },
+        AppServerEvent::Disconnected {
+            message: "foreign disconnected".into(),
+        },
+    ] {
+        app.handle_backend_event(
+            &server,
+            AppServerSessionEvent {
+                backend_id: foreign,
+                event,
+            },
+        )
+        .await;
+    }
+    assert!(!app.reconnect.offline);
+    assert!(
+        !app.pending_app_server_requests
+            .contains_server_request(&request)
+    );
+    assert_eq!(app.chat_widget.capture_thread_input_state(), input);
+    assert!(requests.lock().unwrap().is_empty());
+    assert!(events.try_recv().is_err());
+    {
+        let store = app.thread_event_channels[&id].store.lock().await;
+        assert_eq!(store.active_turn_id(), None);
+        assert!(store.pending_replay_requests().is_empty());
+    }
+    app.handle_backend_event(
+        &server,
+        AppServerSessionEvent {
+            backend_id: server.backend_id(),
+            event: AppServerEvent::ServerNotification(Box::new(turn_started_notification(
+                id,
+                "owned-turn",
+            ))),
+        },
+    )
+    .await;
+    assert_eq!(
+        app.thread_event_channels[&id]
+            .store
+            .lock()
+            .await
+            .active_turn_id(),
+        Some("owned-turn")
+    );
+    server.shutdown().await?;
+    proxy.await??;
+    Ok(())
+}
+
+#[tokio::test]
+async fn transport_events_retain_the_session_backend() -> Result<()> {
+    let app = make_test_app().await;
+    let (mut server, _, proxy) =
+        session_lifecycle_requests::start_recording_remote_app_server(&app.config).await?;
+    let started = server.start_thread(&app.config).await?;
+    server
+        .thread_settings_update(codex_app_server_protocol::ThreadSettingsUpdateParams {
+            thread_id: started.session.thread_id.to_string(),
+            permissions: Some(":read-only".into()),
+            ..Default::default()
+        })
+        .await?;
+    let event = tokio::time::timeout(
+        std::time::Duration::from_secs(/*secs*/ 5),
+        server.next_event(),
+    )
+    .await?
+    .expect("settings update emits an event");
+    assert_eq!(event.backend_id, server.backend_id());
+    server.shutdown().await?;
+    proxy.await??;
+    Ok(())
+}
diff --git a/codex-rs/tui/src/app/tests/background_exit_tests.rs b/codex-rs/tui/src/app/tests/background_exit_tests.rs
index 3d2c8066de..d9d351ccef 100644
--- a/codex-rs/tui/src/app/tests/background_exit_tests.rs
+++ b/codex-rs/tui/src/app/tests/background_exit_tests.rs
@@ -467,7 +467,8 @@ async fn exit_interrupts_before_requesting_shutdown() -> Result<()> {
                 .next_event()
                 .await
                 .expect("app-server event stream should remain open");
-            if let codex_app_server_client::AppServerEvent::ServerNotification(notification) = event
+            if let codex_app_server_client::AppServerEvent::ServerNotification(notification) =
+                event.event
             {
                 match notification.as_ref() {
                     ServerNotification::TurnStarted(notification)
diff --git a/codex-rs/tui/src/app/tests/navigation_reconnect_tests.rs b/codex-rs/tui/src/app/tests/navigation_reconnect_tests.rs
index d34ee7d38d..5f8a8e5381 100644
--- a/codex-rs/tui/src/app/tests/navigation_reconnect_tests.rs
+++ b/codex-rs/tui/src/app/tests/navigation_reconnect_tests.rs
@@ -272,7 +272,7 @@ async fn reconnect_daemon_command_center_after_socket_replacement_without_a_conv
                 "Waiting for active turns.".into(),
             );
         }
-        app.handle_app_server_event(&session, disconnected).await;
+        app.handle_backend_event(&session, disconnected).await;
         assert!(app.reconnect.offline);
         assert!(app.agents_overview.last_messages.is_empty());
         assert!(refresh.await.unwrap_err().is_cancelled());
diff --git a/codex-rs/tui/src/app/tests/realtime_handoff_e2e.rs b/codex-rs/tui/src/app/tests/realtime_handoff_e2e.rs
index 6907784de5..38a395e89f 100644
--- a/codex-rs/tui/src/app/tests/realtime_handoff_e2e.rs
+++ b/codex-rs/tui/src/app/tests/realtime_handoff_e2e.rs
@@ -158,7 +158,7 @@ async fn delegated_core_events_keep_private_output_hidden_and_deliver_final_spee
         loop {
             tokio::select! {
                 event = app_server.next_event() => {
-                    app.handle_app_server_event(
+                    app.handle_backend_event(
                         &app_server,
                         event.expect("embedded app-server should stay connected"),
                     ).await;
@@ -268,9 +268,9 @@ async fn delegated_core_events_keep_private_output_hidden_and_deliver_final_spee
             tokio::select! {
                 event = app_server.next_event() => {
                     let event = event.expect("embedded app-server should stay connected");
-                    let completed = matches!(&event, AppServerEvent::ServerNotification(notification)
+                    let completed = matches!(&event.event, AppServerEvent::ServerNotification(notification)
                         if matches!(notification.as_ref(), ServerNotification::TurnCompleted(_)));
-                    app.handle_app_server_event(&app_server, event).await;
+                    app.handle_backend_event(&app_server, event).await;
                     app.drain_active_thread_events(&mut tui).await?;
                     if completed {
                         break Ok::<_, color_eyre::Report>(());
diff --git a/codex-rs/tui/src/app/tests/recap_generation_tests.rs b/codex-rs/tui/src/app/tests/recap_generation_tests.rs
index 6199df7fd2..2aeaa2b39c 100644
--- a/codex-rs/tui/src/app/tests/recap_generation_tests.rs
+++ b/codex-rs/tui/src/app/tests/recap_generation_tests.rs
@@ -160,7 +160,7 @@ stream_max_retries = 0
                 }
                 event = app_server.next_event() => {
                     let event = event.expect("app-server event stream");
-                    app.handle_app_server_event(&app_server, event).await;
+                    app.handle_backend_event(&app_server, event).await;
                 }
             }
         }
diff --git a/codex-rs/tui/src/app/tests/resume_shutdown_tests.rs b/codex-rs/tui/src/app/tests/resume_shutdown_tests.rs
index 6daf28c9c6..8169741404 100644
--- a/codex-rs/tui/src/app/tests/resume_shutdown_tests.rs
+++ b/codex-rs/tui/src/app/tests/resume_shutdown_tests.rs
@@ -39,7 +39,7 @@ async fn thread_close_exits_only_when_displayed_thread_is_unloaded() -> Result<(
     server.thread_unsubscribe(thread_id).await?;
     let closed = tokio::time::timeout(Duration::from_secs(/*secs*/ 5), async {
         while let Some(event) = server.next_event().await {
-            if matches!(&event,
+            if matches!(&event.event,
                 AppServerEvent::ServerNotification(notification)
                     if matches!(notification.as_ref(), ServerNotification::ThreadClosed(closed)
                         if closed.thread_id == thread_id.to_string()))
@@ -50,7 +50,7 @@ async fn thread_close_exits_only_when_displayed_thread_is_unloaded() -> Result<(
         panic!("server event stream ended before the thread closed");
     })
     .await?;
-    app.handle_app_server_event(&server, closed).await;
+    app.handle_backend_event(&server, closed).await;
     app.drain_active_thread_events(&mut tui).await?;
     assert!(
         std::iter::from_fn(|| events.try_recv().ok())
diff --git a/codex-rs/tui/src/app/tests/safety_buffering.rs b/codex-rs/tui/src/app/tests/safety_buffering.rs
index 71a8f2b5bb..1dcfae9370 100644
--- a/codex-rs/tui/src/app/tests/safety_buffering.rs
+++ b/codex-rs/tui/src/app/tests/safety_buffering.rs
@@ -122,7 +122,7 @@ async fn next_turn_started(
         .await
         .expect("app-server should emit a turn/start event")
         .expect("app-server event stream should remain open");
-        let started_turn_id = if let AppServerEvent::ServerNotification(notification) = &event
+        let started_turn_id = if let AppServerEvent::ServerNotification(notification) = &event.event
             && let ServerNotification::TurnStarted(notification) = notification.as_ref()
             && notification.thread_id == thread_id.to_string()
         {
@@ -130,7 +130,7 @@ async fn next_turn_started(
         } else {
             None
         };
-        app.handle_app_server_event(app_server, event).await;
+        app.handle_backend_event(app_server, event).await;
         drain_active_thread_events(app);
         if let Some(turn_id) = started_turn_id {
             return turn_id;
@@ -152,7 +152,7 @@ async fn wait_for_turn_completed(
         .expect("app-server should emit a turn/completed event")
         .expect("app-server event stream should remain open");
         let completed = matches!(
-            &event,
+            &event.event,
             AppServerEvent::ServerNotification(notification)
                 if matches!(
                     notification.as_ref(),
@@ -160,7 +160,7 @@ async fn wait_for_turn_completed(
                         if notification.thread_id == thread_id.to_string()
                 )
         );
-        app.handle_app_server_event(app_server, event).await;
+        app.handle_backend_event(app_server, event).await;
         drain_active_thread_events(app);
         if completed {
             return;
@@ -315,7 +315,7 @@ stream_max_retries = 0
         )
         .await?
         .expect("app-server remains open");
-        let committed_id = if let AppServerEvent::ServerNotification(notification) = &event
+        let committed_id = if let AppServerEvent::ServerNotification(notification) = &event.event
             && let ServerNotification::ItemCompleted(item) = notification.as_ref()
             && let ThreadItem::UserMessage {
                 content, client_id, ..
@@ -326,7 +326,7 @@ stream_max_retries = 0
         } else {
             None
         };
-        app.handle_app_server_event(&app_server, event).await;
+        app.handle_backend_event(&app_server, event).await;
         if let Some(client_id) = committed_id {
             let saved_input = if via_overview {
                 assert!(!app.thread_event_channels.contains_key(&thread_id));
@@ -429,7 +429,7 @@ async fn drive_until_request_count(
             () = server.wait_for_request_count(expected_request_count) => return,
             event = app_server.next_event() => {
                 let event = event.expect("app-server event stream should remain open");
-                app.handle_app_server_event(app_server, event).await;
+                app.handle_backend_event(app_server, event).await;
                 drain_active_thread_events(app);
             }
             () = &mut timeout => {
diff --git a/codex-rs/tui/src/app/tests/streaming_interleave_e2e.rs b/codex-rs/tui/src/app/tests/streaming_interleave_e2e.rs
index f763f65e72..a1db23cfa9 100644
--- a/codex-rs/tui/src/app/tests/streaming_interleave_e2e.rs
+++ b/codex-rs/tui/src/app/tests/streaming_interleave_e2e.rs
@@ -118,9 +118,9 @@ async fn command_start_before_message_completion_does_not_duplicate_preamble() -
             tokio::select! {
                 event = app_server.next_event() => {
                     let event = event.expect("embedded app-server should stay connected");
-                    let turn_completed = matches!(&event, AppServerEvent::ServerNotification(notification)
+                    let turn_completed = matches!(&event.event, AppServerEvent::ServerNotification(notification)
                         if matches!(notification.as_ref(), ServerNotification::TurnCompleted(_)));
-                    if let AppServerEvent::ServerNotification(notification) = &event {
+                    if let AppServerEvent::ServerNotification(notification) = &event.event {
                         match notification.as_ref() {
                             ServerNotification::AgentMessageDelta(delta) if delta.delta == PREAMBLE => {
                                 observed_order.push("agent delta");
@@ -157,7 +157,7 @@ async fn command_start_before_message_completion_does_not_duplicate_preamble() -
                             _ => {}
                         }
                     }
-                    app.handle_app_server_event(&app_server, event).await;
+                    app.handle_backend_event(&app_server, event).await;
                     app.drain_active_thread_events(&mut tui).await?;
                     if turn_completed {
                         break Ok::<_, color_eyre::Report>(());
diff --git a/codex-rs/tui/src/app/thread_title_tests.rs b/codex-rs/tui/src/app/thread_title_tests.rs
index ca73ee8d30..c8161ef53a 100644
--- a/codex-rs/tui/src/app/thread_title_tests.rs
+++ b/codex-rs/tui/src/app/thread_title_tests.rs
@@ -314,7 +314,7 @@ async fn check_thread_title_generation(scenario: TitleScenario) -> color_eyre::R
 
     enum TitleDriveEvent {
         Ui(Box<AppEvent>),
-        Server(AppServerEvent),
+        Server(crate::app_server_session::AppServerSessionEvent),
         RequestStarted,
     }
 
@@ -347,7 +347,7 @@ async fn check_thread_title_generation(scenario: TitleScenario) -> color_eyre::R
                 app.handle_event(&mut tui, &mut app_server, *event).await?;
             }
             TitleDriveEvent::Server(event) => {
-                if let AppServerEvent::ServerNotification(notification) = &event
+                if let AppServerEvent::ServerNotification(notification) = &event.event
                     && let ServerNotification::ThreadStarted(started) = notification.as_ref()
                     && started.thread.ephemeral
                 {
@@ -356,13 +356,13 @@ async fn check_thread_title_generation(scenario: TitleScenario) -> color_eyre::R
                         Some(ThreadSource::Feature("thread_title".to_string())),
                     );
                 }
-                if let AppServerEvent::ServerNotification(notification) = &event
+                if let AppServerEvent::ServerNotification(notification) = &event.event
                     && let ServerNotification::TurnCompleted(completed) = notification.as_ref()
                     && Some(&completed.thread_id) == temporary_thread_id.as_ref()
                 {
                     interrupted = completed.turn.status == TurnStatus::Interrupted;
                 }
-                app.handle_app_server_event(&app_server, event).await;
+                app.handle_backend_event(&app_server, event).await;
             }
             TitleDriveEvent::RequestStarted => {
                 let name = "Keep this title".to_string();
diff --git a/codex-rs/tui/src/app_server_session.rs b/codex-rs/tui/src/app_server_session.rs
index 008203eff6..38bd2c21e4 100644
--- a/codex-rs/tui/src/app_server_session.rs
+++ b/codex-rs/tui/src/app_server_session.rs
@@ -4,6 +4,7 @@
 //! request/response plumbing out of `App` and `ChatWidget`.
 
 mod daybreak_api_key_compat;
+mod events;
 mod external_agent_config;
 pub(crate) mod fs;
 mod history;
@@ -22,6 +23,7 @@ mod web_search;
 #[path = "app_server_session/collaboration_catalog_tests.rs"]
 mod collaboration_catalog_tests;
 
+pub(crate) use events::AppServerSessionEvent;
 pub(crate) use history::HISTORY_ITEM_PAGE_LIMIT;
 pub(crate) use history::HISTORY_ITEM_SCAN_LIMIT;
 pub(crate) use history::HistoryHydrationScope;
@@ -43,7 +45,6 @@ use crate::status::StatusAccountDisplay;
 use crate::status::plan_type_display_name;
 use crate::terminal_visualization_instructions::with_terminal_visualization_instructions;
 use codex_app_server_client::AppServerClient;
-use codex_app_server_client::AppServerEvent;
 use codex_app_server_client::AppServerPath;
 use codex_app_server_client::AppServerRequestHandle;
 use codex_app_server_client::TypedRequestError;
@@ -854,8 +855,14 @@ impl AppServerSession {
             .map_err(|err| bootstrap_request_error("account/read failed during TUI bootstrap", err))
     }
 
-    pub(crate) async fn next_event(&mut self) -> Option<AppServerEvent> {
-        self.client.next_event().await
+    pub(crate) async fn next_event(&mut self) -> Option<AppServerSessionEvent> {
+        self.client
+            .next_event()
+            .await
+            .map(|event| AppServerSessionEvent {
+                backend_id: self.backend_id,
+                event,
+            })
     }
 
     #[cfg(test)]
diff --git a/codex-rs/tui/src/app_server_session/events.rs b/codex-rs/tui/src/app_server_session/events.rs
new file mode 100644
index 0000000000..3cb42f9f48
--- /dev/null
+++ b/codex-rs/tui/src/app_server_session/events.rs
@@ -0,0 +1,10 @@
+//! Retains the logical backend that produced a session event before UI dispatch.
+//! Backend identity survives reconnects; it is not a transport generation or wire ID.
+
+use crate::backend_id::BackendId;
+use codex_app_server_client::AppServerEvent;
+
+pub(crate) struct AppServerSessionEvent {
+    pub(crate) backend_id: BackendId,
+    pub(crate) event: AppServerEvent,
+}
diff --git a/codex-rs/tui/src/app_server_session/external_agent_config_tests.rs b/codex-rs/tui/src/app_server_session/external_agent_config_tests.rs
index 2385514767..59b61e6814 100644
--- a/codex-rs/tui/src/app_server_session/external_agent_config_tests.rs
+++ b/codex-rs/tui/src/app_server_session/external_agent_config_tests.rs
@@ -3,6 +3,7 @@
 use super::*;
 use crate::external_agent_config_migration::flow::ExternalAgentConfigMigrationFlowOutcome;
 use crate::external_agent_config_migration::flow::handle_external_agent_config_migration_prompt;
+use codex_app_server_client::AppServerEvent;
 use codex_app_server_protocol::JSONRPCMessage;
 use codex_app_server_protocol::ServerNotification;
 use futures::SinkExt;
@@ -103,7 +104,9 @@ async fn external_agent_config_migration_over_shared_transport() -> Result<()> {
         for (import_id, consumed) in [("other-client", false), ("this-client", true)] {
             let event =
                 tokio::time::timeout(Duration::from_secs(/*secs*/ 5), session.next_event()).await?;
-            let Some(AppServerEvent::ServerNotification(notification)) = event else {
+            let Some(AppServerEvent::ServerNotification(notification)) =
+                event.map(|event| event.event)
+            else {
                 panic!("expected import completion");
             };
             let ServerNotification::ExternalAgentConfigImportCompleted(notification) =
diff --git a/codex-rs/tui/src/app_server_session/reasoning_defaults_tests.rs b/codex-rs/tui/src/app_server_session/reasoning_defaults_tests.rs
index d5fdc6b518..904187679f 100644
--- a/codex-rs/tui/src/app_server_session/reasoning_defaults_tests.rs
+++ b/codex-rs/tui/src/app_server_session/reasoning_defaults_tests.rs
@@ -2,6 +2,7 @@
 
 use super::*;
 use crate::legacy_core::config::ConfigBuilder;
+use codex_app_server_client::AppServerEvent;
 use codex_app_server_protocol::ServerNotification;
 use core_test_support::responses;
 use pretty_assertions::assert_eq;
@@ -155,7 +156,7 @@ stream_max_retries = 0
                 .await?;
             tokio::time::timeout(std::time::Duration::from_secs(/*secs*/ 30), async {
                 while let Some(event) = app_server.next_event().await {
-                    if let AppServerEvent::ServerNotification(notification) = event
+                    if let AppServerEvent::ServerNotification(notification) = event.event
                         && let ServerNotification::TurnCompleted(completed) = *notification
                     {
                         assert_eq!(
diff --git a/codex-rs/tui/src/app_server_session/rollout_history_tests.rs b/codex-rs/tui/src/app_server_session/rollout_history_tests.rs
index ecce710de8..fb315da585 100644
--- a/codex-rs/tui/src/app_server_session/rollout_history_tests.rs
+++ b/codex-rs/tui/src/app_server_session/rollout_history_tests.rs
@@ -83,7 +83,7 @@ async fn remote_resume_restores_saved_server_profile_without_permission_override
     tokio::time::timeout(std::time::Duration::from_secs(5), async {
         loop {
             if let Some(codex_app_server_client::AppServerEvent::ServerNotification(notification)) =
-                server.next_event().await
+                server.next_event().await.map(|event| event.event)
                 && let codex_app_server_protocol::ServerNotification::ThreadSettingsUpdated(
                     settings,
                 ) = *notification
diff --git a/codex-rs/tui/src/app_server_session/workspace_roots_tests.rs b/codex-rs/tui/src/app_server_session/workspace_roots_tests.rs
index 525eed5ece..7edfc83ae0 100644
--- a/codex-rs/tui/src/app_server_session/workspace_roots_tests.rs
+++ b/codex-rs/tui/src/app_server_session/workspace_roots_tests.rs
@@ -3,6 +3,7 @@
 use super::*;
 use crate::legacy_core::config::ConfigBuilder;
 use crate::legacy_core::config::ConfigOverrides;
+use codex_app_server_client::AppServerEvent;
 use codex_app_server_protocol::ServerNotification;
 use core_test_support::responses;
 use pretty_assertions::assert_eq;
@@ -112,7 +113,7 @@ stream_max_retries = 0
                     .await?;
                 tokio::time::timeout(std::time::Duration::from_secs(/*secs*/ 30), async {
                     while let Some(event) = app_server.next_event().await {
-                        if let AppServerEvent::ServerNotification(notification) = event
+                        if let AppServerEvent::ServerNotification(notification) = event.event
                             && let ServerNotification::TurnCompleted(completed) = *notification
                         {
                             assert_eq!(
diff --git a/codex-rs/tui/src/dynamic_tools_tests.rs b/codex-rs/tui/src/dynamic_tools_tests.rs
index f6b7a33af2..86049ce6cd 100644
--- a/codex-rs/tui/src/dynamic_tools_tests.rs
+++ b/codex-rs/tui/src/dynamic_tools_tests.rs
@@ -236,7 +236,7 @@ stream_max_retries = 0
     assert_eq!(expected["page"]["order"], "newest_first");
     tokio::time::timeout(Duration::from_secs(/*secs*/ 30), async {
         while let Some(event) = model_server.next_event().await {
-            match event {
+            match event.event {
                 codex_app_server_client::AppServerEvent::ServerRequest(request) => {
                     if let codex_app_server_protocol::ServerRequest::DynamicToolCall {
                         request_id,
diff --git a/codex-rs/tui/src/managed_worktree_model_tests.rs b/codex-rs/tui/src/managed_worktree_model_tests.rs
index 2f66b7cf68..4e2d4cb77c 100644
--- a/codex-rs/tui/src/managed_worktree_model_tests.rs
+++ b/codex-rs/tui/src/managed_worktree_model_tests.rs
@@ -56,7 +56,7 @@ async fn model_call(
     let approvals = tokio::time::timeout(Duration::from_secs(/*secs*/ 30), async {
         let mut approvals = 0;
         while let Some(event) = server.next_event().await {
-            match event {
+            match event.event {
                 AppServerEvent::ServerRequest(request) => {
                     let ServerRequest::McpServerElicitationRequest { request_id, params } = *request else { panic!("unexpected server request: {request:?}"); };
                     assert_eq!(params.thread_id, thread);
diff --git a/codex-rs/tui/src/managed_worktree_tools_tests.rs b/codex-rs/tui/src/managed_worktree_tools_tests.rs
index ab59305251..d799c52dd3 100644
--- a/codex-rs/tui/src/managed_worktree_tools_tests.rs
+++ b/codex-rs/tui/src/managed_worktree_tools_tests.rs
@@ -152,7 +152,7 @@ async fn creation_attaches_to_original_task_and_survives_service_restart_scenari
         .await?;
     tokio::time::timeout(Duration::from_secs(20), async {
         loop {
-            if matches!(server.next_event().await, Some(codex_app_server_client::AppServerEvent::ServerNotification(notification)) if matches!(notification.as_ref(), codex_app_server_protocol::ServerNotification::TurnCompleted(_))) { break; }
+            if matches!(server.next_event().await, Some(event) if matches!(&event.event, codex_app_server_client::AppServerEvent::ServerNotification(notification) if matches!(notification.as_ref(), codex_app_server_protocol::ServerNotification::TurnCompleted(_)))) { break; }
         }
     }).await?;
     let tools = ManagedWorktreeTools::new(&config)
diff --git a/codex-rs/tui/src/onboarding/onboarding_screen.rs b/codex-rs/tui/src/onboarding/onboarding_screen.rs
index 626e545637..a2843b0e5d 100644
--- a/codex-rs/tui/src/onboarding/onboarding_screen.rs
+++ b/codex-rs/tui/src/onboarding/onboarding_screen.rs
@@ -764,7 +764,7 @@ async fn run_onboarding_screen_inner(
                 }
             }, if app_server.is_some() => {
                 if let Some(event) = event {
-                    match event {
+                    match event.event {
                         AppServerEvent::ServerNotification(notification) => {
                             onboarding_screen.handle_app_server_notification(*notification);
                         }
diff --git a/codex-rs/tui/src/resume_picker_transcript_preview_tests.rs b/codex-rs/tui/src/resume_picker_transcript_preview_tests.rs
index 53b09f3dd8..0750e3eb76 100644
--- a/codex-rs/tui/src/resume_picker_transcript_preview_tests.rs
+++ b/codex-rs/tui/src/resume_picker_transcript_preview_tests.rs
@@ -391,7 +391,7 @@ async fn transcript_preview_for_history_mode(
                     panic!("app-server event stream closed before turn completed");
                 };
                 if matches!(
-                    event,
+                    event.event,
                     AppServerEvent::ServerNotification(notification)
                         if matches!(notification.as_ref(), ServerNotification::TurnCompleted(_))
                 ) {