Context

Implement robust error handling for all LLM API calls. Production reliability requires graceful handling of transient failures, rate limits, and provider outages.

Acceptance Criteria

• Exponential backoff for transient errors (429, 500, 503)
• Configurable maximum retry count per provider
• Rate limiting per provider (respect API rate limits)
• Automatic fallback to alternate provider/model on persistent failure
• Timeout handling with configurable duration
• Structured error types: RateLimitError, AuthError, TimeoutError, ProviderUnavailableError
• Clear error messages with actionable context
• Unit tests with simulated failures for each error type
• Integration test for fallback chain activation

Dependencies

• Depends on Implement provider adapter layer (direct API or via LiteLLM) #5 (provider adapter layer implementation)

Design Spec Reference

Section 9.1 — Provider Interface (error handling requirements)