404 when redirecting in server action with subdomain rewrite rule

[lukemorton]

Link to the code that reproduces this issue

https://github.com/lukemorton/next-testing

To Reproduce

1. Add admin.localhost to /etc/hosts
2. Run development server
3. Navigate to http://admin.localhost:3000/a
4. Submit form

Current vs. Expected behavior

When you submit the form, the redirect in the server action attempts to redirect to /b but 404s instead even though the URL exists. If you refresh the page works.

In the example attached there is also a <Link /> on /a which navigates fine to /b.

Appears to be an issue with redirect specifically in server actions.

Could not reproduce without the subdomain rewrite rule in next.config.mjs.

Could not reproduce when redirecting with relative URLs — changing from redirect("/b") to redirect("./b") fixes the issue.

I have been able to reproduce on Vercel with similar subdomain rewrite rule so not just related to localhost.

Expected behaviour: no 404 occurs when redirecting in a server action when I have rewrite rules in my application.

Provide environment information

Operating System:
  Platform: darwin
  Arch: arm64
  Version: Darwin Kernel Version 22.1.0: Sun Oct  9 20:15:52 PDT 2022; root:xnu-8792.41.9~2/RELEASE_ARM64_T8112
  Available memory (MB): 24576
  Available CPU cores: 8
Binaries:
  Node: 20.13.1
  npm: 10.7.0
  Yarn: 1.22.19
  pnpm: N/A
Relevant Packages:
  next: 14.2.3 // Latest available version is detected (14.2.3).
  eslint-config-next: 14.2.3
  react: 18.3.1
  react-dom: 18.3.1
  typescript: 5.4.5
Next.js Config:
  output: N/A

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

Navigation

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

next dev (local), Vercel (Deployed)

Additional context

This issue started in 14.2.1. Appears to be fine in 14.1.3 and so we are holding back any further updates at our organisation.

[igorxmath]

I'm having the same issue with rewrites in middleware. Every time a redirect is called with server actions, Next.js shows a 404 page. However, when I reload the browser, the page loads correctly.

[lukemorton]

@igorxmath Good point about refreshing. A refresh after the 404 does indeed show the right page.

Only consistent fix I’ve found is to start redirect URL with a dot “./location” instead of “/location” or fully qualified domain, e.g. “https://example.com/location”. That’s if redirecting to another location on the same domain. I have not tested cross domain redirects after a server action.