[Bug]: Content-Length header is added to GET requests following a redirect when using request interceptor

[cjbhaines]

Version

1.52.0

Steps to reproduce

I am using the following request interceptor:

await page.route(async (route: Route) => {
  const request = route.request();
  const headers = request.headers();

  headers["My-Extra-Header"] = "Extra-Header-Value";

  await route.continue({
    headers: headers,
  });
});

(I'm not sure if the interceptor is affecting anything or if this would happen without it, but I thought I would mention it anyway)

After a POST request to a server, which returns a 302 redirect as the result, and when Playwright is set to follow redirects automatically, the Content-Length header from the original POST request is included with the GET request to the redirect URI:

General
URL: Omitted
Method: GET
Status Code: 400

Request Headers
Host: Omitted
Cookie: Omitted
user-agent: Mozilla/5.0 (X11; Linux x86_64; rv:137.0) Gecko/20100101 Firefox/137.0
accept: text/html,application/xhtml+xml,application/xml;q=0.9,/;q=0.8
accept-language: en-US
accept-encoding: gzip, deflate, br, zstd
content-type: application/x-www-form-urlencoded
content-length: 47
referer: Omitted
origin: Omitted
upgrade-insecure-requests: 1
sec-fetch-dest: document
sec-fetch-mode: navigate
sec-fetch-site: same-origin
sec-fetch-user: ?1
connection: keep-alive
My-Extra-Header: Extra-Header-Value

Time
Start: 7.1s
Duration: 7ms

Content-Length is not valid for GET requests, so when this happens against CloudFront it rejects the request:

Expected behavior

The Content-Length header is never included for HTTP Verbs that do not have a body.

Actual behavior

The Content-Length header was included in the request, causing an error with CloudFront.

Additional context

NOTE: This only happens with Firefox and Safari, it is not happening with Chromium based browsers. I can confirm that this exact set up works fine with Chrome and I cannot see a Content-Length header in the network logs on Chrome.

Environment

System:
  OS: macOS 15.3.1
  Memory: 84.78 MB / 36.00 GB
Binaries:
  Node: 18.20.4 - ~/.nvm/versions/node/v18.20.4/bin/node
  npm: 10.7.0 - ~/.nvm/versions/node/v18.20.4/bin/npm
  pnpm: 9.9.0 - ~/.nvm/versions/node/v18.20.4/bin/pnpm
Languages:
  Bash: 5.2.32 - /opt/homebrew/bin/bash

[yury-s]

I can only reproduce it in Firefox (at least on macOS and Linux).

[cjbhaines]

Thanks for picking this up @yury-s! I've not actually seen this happen again in Safari since I raised this report, so that might be a red herring, glad you can reproduce in Firefox though!