Why use error codes in addition to error messages?

Explanation

Error codes provide stable, machine-readable identifiers for specific error conditions, complementing human-readable messages. They enable programmatic error handling (switch on code rather than parsing messages), internationalization (translate messages while codes stay constant), API contracts (clients handle specific codes), and analytics (group errors by code). Codes should be stable across versions, well-documented, and follow a consistent naming convention (e.g., AUTH_INVALID_TOKEN, DB_CONNECTION_LOST).