Sharing middleware between FastMCP and FastAPI

[ammmir]

I have a middleware that I'm using with FastAPI that I'm trying to reuse in FastMCP in the spirit of DRY:

class AuthMiddleware:
    def __init__(self, app):
        self.app = app

    async def __call__(self, scope, receive, send):
        if scope["type"] not in ["http", "websocket"]:
            return await self.app(scope, receive, send)

        user_id = ... # fetch from db based on Authorization header

        scope["state"] = {
            "user_id": user_id
        }

        return await self.app(scope, receive, send)

The problem is, the State object seems to not have anything in it in my MCP tool:

@mcp.tool()
async def hello(ctx: Context) -> dict:
    user_id = get_http_request().state.user_id
    return {
        "user_id": user_id
    }

It's blank

AttributeError: 'State' object has no attribute 'user_id'

I'm adding the middleware like:

app.add_middleware(AuthMiddleware)
mcp_app.add_middleware(AuthMiddleware)

Any ideas what I'm doing wrong?

[Idotr1997]

have you managed to do that?
i want to do the same thing