| Authentication / permission | Check your key and model scope. Do not automatically retry. |
| Invalid input / unsupported capability | Correct the input. Never silently remove fields. |
| Insufficient credits / cap too low | Review quantity, fallback, and the quote before a new submission. |
| Provider not configured | Expected for preview models. No real successful output is available. |
| Upstream result unknown | Keep the task ID and query; do not recreate the task. |
| Rate limit | Respect Retry-After and use bounded backoff. |