Guidewire Common Errors
Overview
Fix 400 (validation), 401 (OAuth token expired), 403 (missing API role), 404 (wrong endpoint path), 409 (stale checksum - re-GET and retry), 422 (business rule violation - read userMessage). Gosu errors: ClassNotFoundException (wrong module), NPE (null entity reference), ValidationException (missing required fields).
For detailed implementation, see: implementation guide