Error Handling Patterns Consistent, robust error handling patterns for production applications. When to Activate - Designing error types or exception hierarchies for a new module or service - Adding retry logic or circuit breakers for unreliable external dependencies - Reviewing API endpoints for missing error handling - Implementing user-facing error messages and feedback - Debugging cascading failures or silent error swallowing Core Principles 1. Fail fast and loudly — surface errors at the boundary where they occur; don't bury them 2. Typed errors over string messages — errors are first-cl…