Chrome extension: stale active-writer lock prevents creating a chat

What issue are you seeing?

When using the ChatGPT/Codex app, sending a message in an existing chat can fail with this error:

Error creating chat
thread <thread-id> already has an active writer

The error blocks creating or continuing the chat. The thread ID has been redacted.

What steps can reproduce the bug?

1. In the ChatGPT/Codex app, open an existing chat thread.
2. Enter and send any message in that chat.
3. Observe the thread <thread-id> already has an active writer error.
4. Close the Codex Chrome extension window and retry sending a message.
5. Observe that the error can persist after the extension window is closed.

What is the expected behavior?

The app should allow a message to be sent when no live writer remains. If another view is actively using the thread, the UI should identify that state and provide a way to recover without requiring the user to restart Chrome or abandon the chat.

Additional information

This was observed on macOS. Closing the Chrome extension window did not clear the lock.

No source file or test is identified in the report. Start by reproducing the stale active-writer error in the Chrome extension on macOS, then trace the writer lifecycle across closing and retrying the extension window; done means a message can be sent after no live writer remains, with a recoverable UI state when another view is active.