Only treat in-progress snapshots as mid-turn

Co-authored-by: Codex <noreply@openai.com>

codex-rs/core/src/thread_manager.rs

@@ -940,7 +940,7 @@ fn snapshot_turn_state(history: &InitialHistory) -> SnapshotTurnState {
         let active_turn_snapshot = builder.active_turn_snapshot();
         if active_turn_snapshot
             .as_ref()
-            .is_some_and(|turn| turn.status == TurnStatus::Interrupted)
+            .is_some_and(|turn| turn.status != TurnStatus::InProgress)
         {
             return SnapshotTurnState {
                 ends_mid_turn: false,

codex-rs/core/src/thread_manager_tests.rs

@@ -9,7 +9,9 @@ use codex_protocol::models::ContentItem;
 use codex_protocol::models::ReasoningItemReasoningSummary;
 use codex_protocol::models::ResponseItem;
 use codex_protocol::openai_models::ModelsResponse;
+use codex_protocol::protocol::AgentMessageEvent;
 use codex_protocol::protocol::TurnStartedEvent;
+use codex_protocol::protocol::UserMessageEvent;
 use core_test_support::responses::mount_models_once;
 use pretty_assertions::assert_eq;
 use std::time::Duration;
@@ -277,6 +279,31 @@ fn interrupted_snapshot_is_not_mid_turn() {
     );
 }
 
+#[test]
+fn completed_legacy_event_history_is_not_mid_turn() {
+    let completed_history = InitialHistory::Forked(vec![
+        RolloutItem::EventMsg(EventMsg::UserMessage(UserMessageEvent {
+            message: "hello".to_string(),
+            images: None,
+            text_elements: Vec::new(),
+            local_images: Vec::new(),
+        })),
+        RolloutItem::EventMsg(EventMsg::AgentMessage(AgentMessageEvent {
+            message: "done".to_string(),
+            phase: None,
+            memory_citation: None,
+        })),
+    ]);
+
+    assert_eq!(
+        snapshot_turn_state(&completed_history),
+        SnapshotTurnState {
+            ends_mid_turn: false,
+            active_turn_id: None,
+        },
+    );
+}
+
 #[tokio::test]
 async fn interrupted_fork_snapshot_does_not_synthesize_turn_id_for_legacy_history() {
     let temp_dir = tempdir().expect("tempdir");