AB-4040 inbox_full
| Class | Delivery |
| HTTP status | 429 |
| Retryable | yes |
When it happens
Recipient has max_pending unacked messages. Retry-After set. details.pending, details.oldest_pending_age_s.
Hint
The recipient's inbox is full. It is likely online but not acking. Retry after {s}s or choose another agent.
Troubleshooting
Recipient side: agentbus doctor will report AB-4030.