debug:fastapi

Resolve FastAPI 422 errors by validating request data against OpenAPI docs and checking Pydantic model definitions. A structured debugging workflow helps reproduce the error, isolate the failing field, apply the correction, and prevent future regressions.

Debug FastAPI dependency injection failures by enabling uvicorn logs to trace resolution errors. A four-phase debugging approach helps reproduce the issue, isolate the misconfigured dependency, fix the injection scope, and prevent similar regressions.

Troubleshoot FastAPI CORS issues by using middleware debugging patterns to inspect headers and origins. Systematically reproduce the cross-origin error, isolate the misconfigured middleware, fix the allowed origins, and prevent regressions.

FastAPI startup circular imports happen when modules reference each other before initialization. Diagnose this by checking uvicorn startup logs, isolating the conflicting import path, restructuring the dependencies, and adding import guards to prevent regressions.

Handle FastAPI async/await and database session issues by tracing execution with uvicorn logs and debug middleware. The structured workflow ensures you reproduce the concurrency bug, isolate the session handling failure, fix the async block, and prevent deadlocks.