| 200 / 201 | Success | — |
| 400 | Validation or precondition failed | Read message; do not retry without changing the request. |
| 401 | Auth failed | Check the API key. Do not retry with the same key. |
| 403 | Forbidden | Check organization_id and space_id. |
| 404 | Resource not found | If a known booking returns 404, remove from your dedupe mapping. |
| 409 | Conflict (rare) | Refresh state via GET /api/bookings/{id} and re-decide. |
| 429 | Rate limit (not enforced today) | Back off exponentially. |
| 5xx | Server error | Retry with backoff: 1s, 2s, 5s, 15s, 1m, give up. Alert a human. |