Hello Vercel Support,

My FastAPI project builds successfully on Vercel, but every request to the deployed backend returns 500 FUNCTION_INVOCATION_FAILED.

The runtime logs show:

1ImportError: cannot import name 'vc_handler'2from 'vercel_runtime.vc_init'34File "/var/task/vc__handler__python.py", line 435Application startup failed. Exiting.

Project configuration:

• Framework: FastAPI
• Python version: 3.12
• Root Directory: backend
• Entry point: main.py
• Application: app = FastAPI(...)

The build completes successfully, including dependency installation, but the generated Python runtime handler fails during initialization before the application starts.

I have checked the application entry point, dependencies, Python version, and deployment configuration.

Could you investigate whether this is a Python runtime or generated-handler issue and advise how to resolve it?

Thank you.