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Example Code

from __future__ import annotations
from typing import Annotated
from fastapi import FastAPI, Depends, Request

app = FastAPI()

def get_value() -> str:
    return "injected"

class AuthHandler:
    def __init__(self, roles: list[str]):
        self.roles = roles

    async def __call__(self, request: Request, value: Annotated[str, Depends(get_value)]):
        return {"value": value, "roles": self.roles}

@app.get("/auth")
async def auth_endpoint(auth: Annotated[dict, Depends(AuthHandler(["ADMIN"]))]):
    return auth

Description

When I try to run this with Python 3.14+ and FastAPI 0.121.x, the endpoint /auth fails to start.
The error mentions unresolved ForwardRef objects, and the dependency parameters are treated as query parameters.

I expected FastAPI to correctly inject the value dependency into the callable class, but it does not work.

Operating System

macOS

Operating System Details

No response

FastAPI Version

FastAPI: 0.121.2

Pydantic Version

Pydantic: 2.1.4

Python Version

Python: 3.14.0

Additional Context

I read about a similar issue caused by from future import annotations affecting callable instances. I’d like guidance on the correct pattern to make callable classes work with sub-dependencies in Python 3.14+ without breaking OpenAPI generation.