feat(core): store turn_id on ResponseItem metadata (#28360)

## Description

This PR is a followup to https://github.com/openai/codex/pull/28355 and
starts assigning `internal_chat_message_metadata_passthrough.turn_id` to
durable Responses API items created during a turn.

The goal is that those items keep the `turn_id` that introduced them
when Codex resends stateless HTTP context, reconstructs history for
resume/fork paths, or reuses websocket response state.

## What changed

- Set `internal_chat_message_metadata_passthrough.turn_id` when missing
as response items enter durable history, initial/replacement history,
inter-agent communication history, and local compaction summaries.
- Preserve existing item turn IDs instead of overwriting them during
persistence, resume reconstruction, compaction, forked history, and
websocket incremental reuse.
- Keep `compaction_trigger` fieldless because it is a request control,
not a durable response item.
- Update focused history/request assertions and fixtures for stateless
requests, websocket incrementals, compaction, thread injection, prompt
debug, and related CI coverage.

codex-rs/core/src/session/mod.rs

@@ -2693,6 +2693,10 @@ impl Session {
     ) -> Cow<'a, [ResponseItem]> {
         let mut items = Cow::Borrowed(items);
         prepare_response_items(items.to_mut());
+        // Most response items get their passthrough turn ID at the durable history boundary.
+        for item in items.to_mut() {
+            item.set_turn_id_if_missing(&turn_context.sub_id);
+        }
         if turn_context.config.features.enabled(Feature::ItemIds) {
             Self::assign_missing_response_item_ids(items)
         } else {
@@ -2784,8 +2788,9 @@ impl Session {
     pub(crate) async fn record_inter_agent_communication(
         &self,
         turn_context: &TurnContext,
-        communication: InterAgentCommunication,
+        mut communication: InterAgentCommunication,
     ) {
+        communication.set_turn_id_if_missing(&turn_context.sub_id);
         let response_item = communication.to_model_input_item();
         let items = self.prepare_conversation_items_for_history(
             turn_context,
@@ -3355,6 +3360,10 @@ impl Session {
         {
             items.push(guardian_developer_message);
         }
+        // New context windows and compaction install these items directly into replacement history.
+        for item in &mut items {
+            item.set_turn_id_if_missing(&turn_context.sub_id);
+        }
         items
     }
 

codex-rs/core/src/session/tests.rs

@@ -152,6 +152,7 @@ use core_test_support::responses::ev_response_created;
 use core_test_support::responses::mount_sse_once;
 use core_test_support::responses::sse;
 use core_test_support::responses::start_mock_server;
+use core_test_support::responses::strip_metadata_from_items;
 use core_test_support::test_codex::local;
 use core_test_support::test_codex::test_codex;
 use core_test_support::test_path_buf;
@@ -1692,6 +1693,67 @@ async fn record_initial_history_reconstructs_resumed_transcript() {
     assert_eq!(expected, history.raw_items());
 }
 
+#[tokio::test]
+async fn record_conversation_items_stamps_missing_turn_id_and_preserves_existing_turn_id() {
+    let (session, turn_context) = make_session_and_context().await;
+    let fresh_item = user_message("fresh");
+    let mut existing_item = assistant_message("existing");
+    existing_item.set_turn_id_if_missing("older-turn");
+
+    session
+        .record_conversation_items(&turn_context, &[fresh_item.clone(), existing_item.clone()])
+        .await;
+
+    let mut expected_fresh_item = fresh_item;
+    expected_fresh_item.set_turn_id_if_missing(&turn_context.sub_id);
+    let expected_items = vec![expected_fresh_item, existing_item];
+    assert_eq!(
+        session.clone_history().await.raw_items(),
+        expected_items.as_slice()
+    );
+}
+
+#[tokio::test]
+async fn record_inter_agent_communication_sets_turn_id_in_rollout_and_resume() {
+    let (mut session, turn_context) = make_session_and_context().await;
+    let rollout_path = attach_thread_persistence(&mut session).await;
+    let communication = InterAgentCommunication::new(
+        AgentPath::root().join("worker").expect("worker path"),
+        AgentPath::root(),
+        Vec::new(),
+        "child done".to_string(),
+        /*trigger_turn*/ false,
+    );
+    let mut expected_item = communication.to_model_input_item();
+    expected_item.set_turn_id_if_missing(&turn_context.sub_id);
+
+    session
+        .record_inter_agent_communication(&turn_context, communication)
+        .await;
+
+    assert_eq!(
+        session.clone_history().await.raw_items(),
+        std::slice::from_ref(&expected_item)
+    );
+
+    session.flush_rollout().await.expect("rollout should flush");
+    let InitialHistory::Resumed(resumed) = RolloutRecorder::get_rollout_history(&rollout_path)
+        .await
+        .expect("read rollout history")
+    else {
+        panic!("expected resumed rollout history");
+    };
+
+    let (resumed_session, _resumed_turn_context) = make_session_and_context().await;
+    resumed_session
+        .record_initial_history(InitialHistory::Resumed(resumed))
+        .await;
+    assert_eq!(
+        resumed_session.clone_history().await.raw_items(),
+        std::slice::from_ref(&expected_item)
+    );
+}
+
 #[tokio::test]
 async fn prepares_image_failures_before_history_insertion() {
     let (session, turn_context, _rx) = make_session_and_context_with_auth_and_config_and_rx(
@@ -1758,7 +1820,7 @@ async fn prepares_image_failures_before_history_insertion() {
         },
         internal_chat_message_metadata_passthrough: None,
     }];
-    assert_eq!(history.raw_items(), expected.as_slice());
+    assert_eq!(strip_metadata_from_items(history.raw_items()), expected);
 }
 
 #[tokio::test]
@@ -8224,7 +8286,7 @@ async fn handle_output_item_done_records_image_save_history_message() {
         ),
     );
     let expected = vec![image_message, item];
-    assert_eq!(history.raw_items(), expected.as_slice());
+    assert_eq!(strip_metadata_from_items(history.raw_items()), expected);
     assert_eq!(
         std::fs::read(&expected_saved_path).expect("saved file"),
         b"foo"
@@ -8267,7 +8329,7 @@ async fn handle_output_item_done_skips_image_save_message_when_save_fails() {
 
     let history = session.clone_history().await;
     let expected = vec![item];
-    assert_eq!(history.raw_items(), expected.as_slice());
+    assert_eq!(strip_metadata_from_items(history.raw_items()), expected);
     assert!(!expected_saved_path.exists());
 }
 
@@ -9019,7 +9081,7 @@ async fn task_finish_emits_turn_item_lifecycle_for_leftover_pending_user_input()
         internal_chat_message_metadata_passthrough: None,
     };
     assert!(
-        history.raw_items().iter().any(|item| item == &expected),
+        strip_metadata_from_items(history.raw_items()).contains(&expected),
         "expected pending input to be persisted into history on turn completion"
     );