First Check

• I added a very descriptive title here.
• I used the GitHub search to find a similar question and didn't find it.
• I searched the FastAPI documentation, with the integrated search.
• I already searched in Google "How to X in FastAPI" and didn't find any information.
• I already read and followed all the tutorial in the docs and didn't find an answer.
• I already checked if it is not related to FastAPI but to Pydantic.
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Commit to Help

• I commit to help with one of those options 👆

Example Code

from fastapi import FastAPI, APIRouter


class MyAPIRouter(APIRouter):
    pass


app = FastAPI(router_class=MyAPIRouter)

Description

I have a custom APIRouter implementation that I want to use in my FastAPI application.

Currently, it's not possible to override the default APIRouter in FastAPI instance.

As far as we can override default APIRoute class on APIRouter level, I guess it also makes sense to be able to override the default APIRouter class on FastAPI level.

My current workaround is to use mount method which is not ideal, because it will eventually miss a lot of features like
for instance openapi generation, etc.

Operating System

Linux, Windows, macOS, Other

Operating System Details

No response

FastAPI Version

0.115.12

Pydantic Version

2.11.4

Python Version

Python 3.10.16

Additional Context

No response