Resolve and retrieve the trace produced for a specific message, identified by the message ID returned from the thread messages endpoint. Returns the same shape as retrieveAgentTrace. Returns 404 when no trace can be resolved for the message — because it predates the trace-retention window, because the message belongs to a different agent than the one in the path, or because the message was not produced by an agent run at all. A non-UUID message ID is rejected at validation with a 400.

Rate limit: shares the trace-list limiter — 30 requests per minute per organization. Responses carry RateLimit-Limit, RateLimit-Remaining, and RateLimit-Reset headers, plus Retry-After on a 429.

{
  "sessionStartHook": {
    "fetchedAt": "2026-07-22T19:03:58.412Z"
  }
}