- Backoff delay = Retry-After + exponential (2s, 4s, 8s, ...)
- If Retry-After exceeds 60s max, give up immediately
- Respects Retry-After header as floor, adds incremental backoff
- Comprehensive unit tests for all backoff paths
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>