Subscribe To Chat

Reconnect to an in-flight chat's SSE stream without sending a new message.

Replays every logged event with index > after_index (the client's anchor from GET /chats/{id}.last_event_index) and then tails the live log — the event log is durable, so this works across workers.

Orphaned-run revival: if the chat looks in-flight but no worker holds its lock and the engine's persisted conversation is unfinished (its worker was SIGKILLed mid-run), this endpoint takes the lock and restarts the turn with message=None so the run continues instead of hanging forever.