V3

codex-rs/tui/src/chatwidget.rs

@@ -108,6 +108,8 @@ struct PatchInFlight {
     working_dir: PathBuf,
 }
 
+const MAX_COMPLETED_UNDO_TURNS: usize = 1;
+
 #[derive(Default)]
 struct PatchUndoHistory {
     trackers: HashMap<String, PatchInFlight>,
@@ -129,6 +131,7 @@ impl PatchUndoHistory {
         let completed = self.take_active_turn()?;
         let count = completed.len();
         self.completed_turns.push(completed);
+        self.prune_completed_turns();
         Some(count)
     }
 
@@ -179,6 +182,12 @@ impl PatchUndoHistory {
         }
     }
 
+    fn prune_completed_turns(&mut self) {
+        while self.completed_turns.len() > MAX_COMPLETED_UNDO_TURNS {
+            self.completed_turns.remove(0);
+        }
+    }
+
     fn begin_undo(&mut self) -> Option<Arc<[AppliedPatchDiff]>> {
         if self.undo_in_progress.is_some() {
             return None;
@@ -198,6 +207,7 @@ impl PatchUndoHistory {
             && !success
         {
             self.completed_turns.push(turn);
+            self.prune_completed_turns();
         }
     }
 

codex-rs/tui/src/chatwidget/tests.rs

@@ -78,6 +78,29 @@ fn upgrade_event_payload_for_tests(mut payload: serde_json::Value) -> serde_json
     payload
 }
 
+#[test]
+fn patch_undo_history_is_bounded() {
+    fn make_diff(label: &str) -> Arc<[AppliedPatchDiff]> {
+        Arc::from(vec![AppliedPatchDiff {
+            diff: format!("diff --git a/{label} b/{label}"),
+            working_dir: PathBuf::from("/repo"),
+        }])
+    }
+
+    let mut history = PatchUndoHistory::new();
+    history.completed_turns.push(make_diff("first"));
+    history.prune_completed_turns();
+    assert_eq!(history.completed_turns.len(), 1);
+
+    history.completed_turns.push(make_diff("second"));
+    history.prune_completed_turns();
+    assert_eq!(history.completed_turns.len(), 1);
+    assert_eq!(
+        history.completed_turns[0][0].diff,
+        "diff --git a/second b/second"
+    );
+}
+
 #[test]
 fn final_answer_without_newline_is_flushed_immediately() {
     let (mut chat, mut rx, _op_rx) = make_chatwidget_manual();