Two sessions running at once both stopped with nothing on screen but `interrupted`. The reason was there and was being thrown away: a usage cap or a rate limit arrives as a synthetic assistant message, `#assistant` dropped it on `is_api_error_message`, and the result that follows reports `interrupted` — a status that carries no error by design. So the one sentence explaining the stop reached nobody. It is emitted as an error now, and the turn still reports how it ended. Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>