Hi! First off, yes, I know fetching in middleware isn't necessarily a good thing, but it's for a concept I will flesh out later.

The issue I'm encountering is that I am trying to fetch data from an API endpoint with a custom header "js_sender".
I also inject client cookies into the request, which I'll get to shortly.

Before executing fetch, I have logged the value of the init variable for fetch and this is what it contains:

{
  headers: {
    js_sender: 'JumpStart Middleware',
    Cookie: '<client cookies>'
  }
}

The problem happens that when I receive the request on my backend, the js_sender cookie is entirely missing, but the cookie header is present:

Headers {
  Host: 'REDACTED',
  'X-Forwarded-Scheme': 'https',
  'X-Forwarded-Proto': 'https',
  'X-Forwarded-For': 'REDACTED',
  'X-Real-IP': 'REDACTED',
  Connection: 'close',
  'cdn-loop': 'cloudflare; loops=1',
  accept: '*/*',
  'accept-encoding': 'gzip, br',
  'cf-ipcountry': 'US',
  'x-middleware-subrequest': 'src/middleware',
  'user-agent': 'Next.js Middleware',
  'cf-visitor': '{"scheme":"https"}',
  'cf-connecting-ip': 'REDACTED',
  'sec-fetch-mode': 'cors',
  'accept-language': '*',
  cookie: '<client cookies>'
}

I cannot replicate it locally, when both NextJS and the backend are running and middleware does the same request. It only seems to happen server-side, and I'm unsure what to do.

Any help would be greatly appreciated!