Request URL is incorrect

[VeryCrazyDog]

Link to the code that reproduces this issue

https://github.com/VeryCrazyDog/nextjs-bug-req-url

To Reproduce

1. Clone the minimal reproducible repo.
2. Run npm ci to install dependencies.
3. Run npm run build to build standalone output.
4. Run node ./.next/standalone/server.js to run the standalone server. It is expected that the server listening on 0.0.0.0 on network.

   ▲ Next.js 15.4.0-canary.34
   - Local:        http://localhost:3000
   - Network:      http://0.0.0.0:3000
   

5. Access http://localhost:3000/get/127.0.0.5/show/127.0.0.1 from browser. The request URL printed is incorrect.

   Request URL: http://0.0.0.0:3000/get/localhost/show/127.0.0.1
   

6. Run npm run dev to run server in development mode.
7. Access http://server-hostname:3000/get/127.0.0.5/show/127.0.0.1 from browser, where server-hostname is the hostname the running server. The request URL is not showing server-hostname.

   Request URL: http://localhost:3000/get/127.0.0.5/show/127.0.0.1
   

Current vs. Expected behavior

Issue 1: Host name is invalid and pathname being altered

When running server using standalone output and accessing http://localhost:3000/get/127.0.0.5/show/127.0.0.1, the request URL printed is:

http://0.0.0.0:3000/get/localhost/show/127.0.0.1

It is expected the printed request URL is the same as the URL being accessed.

http://localhost:3000/get/127.0.0.5/show/127.0.0.1

Issue 2: Host name is incorrect

When running server using development mode and accessing http://server-hostname:3000/get/127.0.0.5/show/127.0.0.1, where server-hostname is the host name the running server, the request URL printed is:

http://localhost:3000/get/127.0.0.5/show/127.0.0.1

It is expected the printed request URL is the same as the URL being accessed.

http://server-hostname:3000/get/127.0.0.5/show/127.0.0.1

Provide environment information

'yarn' is not recognized as an internal or external command,
operable program or batch file.
'pnpm' is not recognized as an internal or external command,
operable program or batch file.

Operating System:
  Platform: win32
  Arch: x64
  Version: Windows 11 Pro
  Available memory (MB): 32426
  Available CPU cores: 12
Binaries:
  Node: 20.11.1
  npm: 10.2.4
  Yarn: N/A
  pnpm: N/A
Relevant Packages:
  next: 15.4.0-canary.34 // Latest available version is detected (15.4.0-canary.34).
  eslint-config-next: N/A
  react: 19.1.0
  react-dom: 19.1.0
  typescript: 5.8.3
Next.js Config:
  output: standalone

Which area(s) are affected? (Select all that apply)

Middleware

Which stage(s) are affected? (Select all that apply)

next dev (local), next start (local), Other (Deployed)

Additional context

For issue pathname being altered, the root cause is because REGEX_LOCALHOST_HOSTNAME is incorrect.

https://regex101.com/r/2KVnEM/1

[zachingle-easygo]

Would love to see this fixed!

Any URLs which have 127.0.0.1 in them will have it rewritten to localhost . This also includes query parameters, which we use on the Kick Public API when performing OAuth authorisation. For any applications which integrate with the public API, and use a callback URL with 127.0.0.1 as their host, it will cause authorisation to fail as we require redirect URIs to match as NextJS is modifying the query parameter. See KickEngineering/KickDevDocs#211 for more info.

URL normalisation definitely seems to be the cause. If I set the skipMiddlewareUrlNormalize option to true in the Next config on the reproduction, it fixes the issue.