- Preserve upstream AI provider HTTP status codes and expose AI-specific error codes for overload, rate limit, unavailable, and generic provider failures.
- Add short retries for transient AI provider 429/5xx chat completion responses, with configurable retry delays.
- Show friendly AI busy/unavailable messages in the report editor instead of raw provider JSON.
- Preserve custom backend error codes in the shared API exception filter.
- Add AI service tests for retry behavior and overload error mapping.
- Update API, feature, and testing documentation for AI proxy retry and error handling.