How to handle exceptions thrown during lifespan startup?

[madduck]

I am developing a FastAPI application with uvicorn, and I have run into an issue where I cannot seem to catch an exception thrown during startup.

The code is below. Yes, I am using FastAPI, but I am reasonably convinced that the issue with with uvicorn. When I run the below, I get this output:

INFO:     Started server process [3478436]
INFO:     Waiting for application startup.
ERROR:    Traceback (most recent call last):
  File "/home/madduck/.tmp/2025-07-09-172139-fastapi-lifespan/.direnv/python-3.13.3/lib/python3.13/site-packages/starlette/routing.py", line 692, in lifespan
    async with self.lifespan_context(app) as maybe_state:
               ~~~~~~~~~~~~~~~~~~~~~^^^^^
  File "/usr/lib/python3.13/contextlib.py", line 214, in __aenter__
    return await anext(self.gen)
           ^^^^^^^^^^^^^^^^^^^^^
  File "/home/madduck/.tmp/2025-07-09-172139-fastapi-lifespan/app.py", line 9, in lifespan
    raise RuntimeError("BOOOOOM")
RuntimeError: BOOOOOM

ERROR:    Application startup failed. Exiting.

Those error messages are coming from uvicorn.

I've raised this issue over at FastAPI, but I was told that FastAPI cannot do anything.

But can I do anything with Uvicorn? The following does not work. Where do I need to catch the exception?

from contextlib import asynccontextmanager
import sys
from fastapi import FastAPI
import uvicorn


@asynccontextmanager
async def lifespan(app):
    raise RuntimeError("BOOOOOM")
    yield


try:
    app = FastAPI(lifespan=lifespan)

except Exception:
    import ipdb; ipdb.set_trace()  # noqa: E402 E702 I001 # fmt: skip
    sys.exit(1)


@app.get("/")
async def root():
    return {"message": "Hello World"}


def main():
    try:
        config = uvicorn.Config(app)
        server = uvicorn.Server(config)
        server.run()

    except* Exception:
        import ipdb; ipdb.set_trace()  # noqa: E402 E702 I001 # fmt: skip


if __name__ == "__main__":
    import sys

    sys.exit(main())

Update FYI, the idea of handling lifespan outside of FastAPI provides a viable approach: fastapi/fastapi#13878 (reply in thread) . Better than nothing…