From 60e7e634bbf42dfd5fb04aa36ebbcb62fdbe40c9 Mon Sep 17 00:00:00 2001
From: Charles Cunningham <ccunningham@openai.com>
Date: Sat, 21 Feb 2026 22:49:52 -0800
Subject: [PATCH] Preserve legacy no-id turn baselines across rollback

---
 codex-rs/core/src/codex.rs                   | 82 ++++++++++++++++++++
 codex-rs/core/src/context_manager/history.rs |  6 +-
 2 files changed, 87 insertions(+), 1 deletion(-)

diff --git a/codex-rs/core/src/codex.rs b/codex-rs/core/src/codex.rs
index aa31da0ac4..3039db8c54 100644
--- a/codex-rs/core/src/codex.rs
+++ b/codex-rs/core/src/codex.rs
@@ -6678,6 +6678,88 @@ mod tests {
         );
     }
 
+    #[tokio::test]
+    async fn record_initial_history_resumed_rollback_with_missing_turn_context_ids_keeps_distinct_baselines()
+     {
+        let (session, turn_context) = make_session_and_context().await;
+        let first_turn_id = "turn-1".to_string();
+        let second_turn_id = "turn-2".to_string();
+
+        let mut first_context_item = turn_context.to_turn_context_item();
+        first_context_item.turn_id = None;
+        first_context_item.model = "model-a".to_string();
+
+        let mut second_context_item = turn_context.to_turn_context_item();
+        second_context_item.turn_id = None;
+        second_context_item.model = "model-b".to_string();
+
+        let rollout_items = vec![
+            RolloutItem::EventMsg(EventMsg::TurnStarted(
+                codex_protocol::protocol::TurnStartedEvent {
+                    turn_id: first_turn_id.clone(),
+                    model_context_window: Some(128_000),
+                    collaboration_mode_kind: ModeKind::Default,
+                },
+            )),
+            RolloutItem::EventMsg(EventMsg::UserMessage(
+                codex_protocol::protocol::UserMessageEvent {
+                    message: "first".to_string(),
+                    images: None,
+                    local_images: Vec::new(),
+                    text_elements: Vec::new(),
+                },
+            )),
+            RolloutItem::TurnContext(first_context_item.clone()),
+            RolloutItem::EventMsg(EventMsg::TurnComplete(
+                codex_protocol::protocol::TurnCompleteEvent {
+                    turn_id: first_turn_id,
+                    last_agent_message: None,
+                },
+            )),
+            RolloutItem::EventMsg(EventMsg::TurnStarted(
+                codex_protocol::protocol::TurnStartedEvent {
+                    turn_id: second_turn_id.clone(),
+                    model_context_window: Some(128_000),
+                    collaboration_mode_kind: ModeKind::Default,
+                },
+            )),
+            RolloutItem::EventMsg(EventMsg::UserMessage(
+                codex_protocol::protocol::UserMessageEvent {
+                    message: "second".to_string(),
+                    images: None,
+                    local_images: Vec::new(),
+                    text_elements: Vec::new(),
+                },
+            )),
+            RolloutItem::TurnContext(second_context_item),
+            RolloutItem::EventMsg(EventMsg::TurnComplete(
+                codex_protocol::protocol::TurnCompleteEvent {
+                    turn_id: second_turn_id,
+                    last_agent_message: None,
+                },
+            )),
+            RolloutItem::EventMsg(EventMsg::ThreadRolledBack(
+                codex_protocol::protocol::ThreadRolledBackEvent { num_turns: 1 },
+            )),
+        ];
+
+        session
+            .record_initial_history(InitialHistory::Resumed(ResumedHistory {
+                conversation_id: ThreadId::default(),
+                history: rollout_items,
+                rollout_path: PathBuf::from("/tmp/resume.jsonl"),
+            }))
+            .await;
+
+        assert_eq!(session.previous_model().await, Some("model-a".to_string()));
+        assert_eq!(
+            serde_json::to_value(session.reference_context_item().await)
+                .expect("serialize seeded reference context item"),
+            serde_json::to_value(Some(first_context_item))
+                .expect("serialize expected reference context item")
+        );
+    }
+
     #[tokio::test]
     async fn record_initial_history_resumed_rollback_skips_only_user_turns() {
         let (session, turn_context) = make_session_and_context().await;
diff --git a/codex-rs/core/src/context_manager/history.rs b/codex-rs/core/src/context_manager/history.rs
index d1fa1828a3..5c1403e56a 100644
--- a/codex-rs/core/src/context_manager/history.rs
+++ b/codex-rs/core/src/context_manager/history.rs
@@ -100,7 +100,11 @@ impl ContextManager {
 
     pub(crate) fn record_regular_turn_baseline(&mut self, item: TurnContextItem) {
         if let Some(top) = self.user_turn_baselines.last_mut()
-            && top.turn_context_item.turn_id == item.turn_id
+            && let (Some(top_turn_id), Some(item_turn_id)) = (
+                top.turn_context_item.turn_id.as_deref(),
+                item.turn_id.as_deref(),
+            )
+            && top_turn_id == item_turn_id
         {
             top.turn_context_item = item.clone();
             top.invalidated_by_following_compaction = false;