Server action - Internal error not handled if middleware is used Server action does not finish request on file size exceeded error

[liri2006]

Link to the code that reproduces this issue

https://github.com/liri2006/next-file-upload-issue

To Reproduce

1. Ensure app uses middleware.ts file
2. Start the app
3. Upload file > 1mb
4. Submit form
5. Check Network tab in browser

Current vs. Expected behavior

Expected:
Error is returned to the client.

Actual:
Request is in permanent "pending" state, so form submit never ends. Error is printed in server logs though .

Provide environment information

Operating System:
  Platform: win32
  Arch: x64
  Version: Windows 11 Pro
  Available memory (MB): 32536
  Available CPU cores: 16
Binaries:
  Node: 22.11.0
  npm: 10.9.0
  Yarn: N/A
  pnpm: 9.12.3
Relevant Packages:
  next: 15.0.4-canary.21 // Latest available version is detected (15.0.4-canary.21).
  eslint-config-next: N/A
  react: 19.0.0-rc-380f5d67-20241113
  react-dom: 19.0.0-rc-380f5d67-20241113
  typescript: 5.3.3
Next.js Config:
  output: N/A

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

Middleware, Runtime

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

next dev (local), Vercel (Deployed)

Additional context

Works as expected if middleware file is deleted.