Page re-export leaks server code to browser

Why this is a good first issue

Server code leaks to browser due to re-exporting pages.

AI Summary

The issue involves server code leaking to the browser when re-exporting pages in the Pages Router, specifically causing module resolution errors. The problem appears to be related to tree-shaking limitations in Next.js. The issue is somewhat clear but requires understanding of Next.js bundling behavior.

Issue Description

Link to the code that reproduces this issue

https://github.com/timheerwagen/re-export-page-server-code-leak

To Reproduce

Install dependencies and start the development server: next dev
The server code for the /index page works.
Navigate to /plugin-page - Server Code leaks to browser (Module not found: Can't resolve 'fs/promises')
Navigate to /component-page - Server Code leaks to browser (Module not found: Can't resolve 'fs/promises')

Current vs. Expected behavior

Only the getServerSideProps function in the pages directory works with server code.

Re-exporting a page, whether within the same application package or an external/workspace package (e.g. plugin), leaks server code to the browser.

The docs state a fix, which has already been used to reproduce the issue: https://nextjs.org/docs/messages/export-all-in-page#possible-ways-to-fix-it (export { default, getServerSideProps } from "@repo/page-plugin/pages/index"; )

Provide environment information

Operating System:
  Platform: win32
  Arch: x64
  Version: Windows 11 Home
  Available memory (MB): 16294
  Available CPU cores: 12
Binaries:
  Node: 24.11.1
  npm: 11.6.2
  Yarn: N/A
  pnpm: 9.0.0
Relevant Packages:
  next: 16.1.0 // Latest available version is detected (16.1.0).
  eslint-config-next: N/A
  react: 19.2.3
  react-dom: 19.2.3
  typescript: N/A
Next.js Config:
  output: N/A

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

Pages Router

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

next dev (local)

Additional context

No response

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