Consecutive slashes in URL trigger routing error and no page renders in browser when Next.js runs behind gateway

Link to the code that reproduces this issue

https://github.com/cosieLq/exampleApp_nextjs/tree/reproduction-double-slash-routing-error

To Reproduce

1. Start the application (npm run dev or npm run start)
2. Start the gateway (node proxy.js)
3. Go to localhost:8000///about
4. Observe browser console and see 'Error: invariant: invalid relative URL, router received...'

Current vs. Expected behavior

I expected no error in browser console and the page to render correctly.

Provide environment information

Operating System:
  Platform: darwin
  Arch: arm64
  Version: Darwin Kernel Version 23.6.0: Wed Jul 31 20:48:52 PDT 2024; root:xnu-10063.141.1.700.5~1/RELEASE_ARM64_T6020
  Available memory (MB): 16384
  Available CPU cores: 12
Binaries:
  Node: 20.15.1
  npm: 10.7.0
  Yarn: 1.22.19
  pnpm: N/A
Relevant Packages:
  next: 15.0.0-canary.179 // Latest available version is detected (15.0.0-canary.179).
  eslint-config-next: N/A
  react: 19.0.0-beta-04b058868c-20240508
  react-dom: 19.0.0-beta-04b058868c-20240508
  typescript: 5.1.3
Next.js Config:
  output: N/A

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

Internationalization (i18n), Navigation, Pages Router

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

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

Additional context

When i18n is disabled in next.config.js, no error will appear and the page renders correctly.

Start with the exampleApp_nextjs reproduction branch, run npm run dev or npm run start alongside node proxy.js, and reproduce the issue at localhost:8000///about. Then compare the behavior with i18n enabled and disabled in next.config.js, tracing the Pages Router navigation path. Done means the browser console has no routing error and the page renders correctly behind the gateway.