I wrote a middleware which is calling external API like this:

import { NextAuthRequest } from 'next-auth/lib';
import { NextResponse } from 'next/server';

import { auth } from './auth';

export default auth((req: NextAuthRequest) => {
  // retrieve the azure idToken
  const token = req.auth?.idToken;
  const pathname = req.nextUrl.pathname.replace('/api/wg', '');

  // rewrite the api url to the WunderGraph API
  const url = new URL(
    pathname + req.nextUrl.search,
    process.env.NEXT_WUNDERGRAPH_URL || 'http://localhost:9991',
  );

  // add the token to the Authorization header
  const newHeaders = new Headers(req.headers);
  newHeaders.set('Authorization', `Bearer ${token}`);

  // rewrite the request to the WunderGraph API
  const response = NextResponse.rewrite(url, {
    request: {
      headers: newHeaders,
    },
  });

  return response;
});

export const config = {
  matcher: ['/api/wg/:function*'],
};

Everything seems to be working fine for simple cases but whenever it is calling Streaming Api which is using EventSource the responses headers like Connection: keep-alive from external API are wiped and I'm getting Connection: closed. When I change it to fetch instead of NextResponse.rewrite:

  ...
  // add the token to the Authorization header
  const newHeaders = new Headers(req.headers);
  newHeaders.set('Authorization', `Bearer ${token}`);

  const data = await fetch(url, { ...req, headers: newHeaders });

  return data;
});
  ...

I'm getting response headers from external API correctly. Am I missing something with NextResponse.rewrite. I think it should not remove response headers from external api.