testProxy breaks axios with Basic Auth

[jokklan]

Link to the code that reproduces this issue

https://github.com/jokklan/nextjs-reproduce-app

To Reproduce

1. Call any endpoint with axios including basic auth credentials in the auth options key (this works)
2. Change experimental.testProxy to true in next.config.ts
3. Make the same axios request as in Added css using aphrodite #1, now it fails with "Request cannot be constructed from a URL that includes credential: https://user:pass@domain/path"

Current vs. Expected behavior

Changing testProxy should not change the behaviour of axios request.

Provide environment information

Operating System:
  Platform: darwin
  Arch: arm64
  Version: Darwin Kernel Version 24.4.0: Fri Apr 11 18:32:50 PDT 2025; root:xnu-11417.101.15~117/RELEASE_ARM64_T6041
  Available memory (MB): 24576
  Available CPU cores: 12
Binaries:
  Node: 22.16.0
  npm: 10.9.2
  Yarn: N/A
  pnpm: N/A
Relevant Packages:
  next: 15.4.2-canary.44 // Latest available version is detected (15.4.2-canary.44).
  eslint-config-next: N/A
  react: 19.1.1
  react-dom: 19.1.1
  typescript: 5.9.2
Next.js Config:
  output: N/A

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

Runtime

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

next dev (local)

Additional context

Changing the axios adapter to fetch is a temporary fix for this issue, it only happens when using the http adapter which is default for node requests.

[Karthikeya-Thatipamula]

Hey I could reproduce this issue with the repo you shared. I’ve worked with Next.js quite a bit and have a good grasp of the basics, so I’d like to take this on. Can you assign me the issue? I’ll work on a fix and add a test to cover it.

[LeeWxx]

@Karthikeya-Thatipamula I just saw your comment. I started working on a fix a few hours ago and have just opened PR #82692. Sorry for the overlap. If there are additional tests or improvements you’d like, please let me know and I’ll incorporate them promptly.