When using SlowAPIASGIMiddleware with anything that streams (like FileResponse or StaticFiles), it crashes with:

RuntimeError: ASGI flow error: Response already started

The problem is in _ASGIMiddlewareResponder.send_wrapper — it sends http.response.start on every http.response.body chunk instead of just the first one. Streaming responses send multiple body chunks with more_body=True, so the second chunk triggers the error because the response was already started.

Easy to reproduce: just mount a StaticFiles directory and request any file through the middleware.