vercel / vercel/next.js

After upgrading to Next.js 16.0.1, the build fails during prerendering of the internal /_not-found route with the following error:

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linear: next
Dominant language
JavaScript
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Description

Link to the code that reproduces this issue

https://github.com/md2docx/mdast2docx/tree/a9078b882ec58f3cdafb68446c8d0c679a1907b8/examples/nextjs

To Reproduce
  1. clone repo and install dependencies
  2. run build command
Current vs. Expected behavior

Current:

Build fails with following error:

Error occurred prerendering page "/_not-found".
Error: Functions cannot be passed directly to Client Components unless you explicitly expose it by marking it with "use server". Or maybe you meant to call this function rather than return it.
  {linkComponent: function i}
                  ^^^^^^^^^^
Export encountered an error on /_not-found/page: /_not-found, exiting the build.

Expected: should build without errors as with next.js 15

Provide environment information
Operating System:
  Platform: win32
  Arch: x64
  Version: Windows 11 Home Single Language
  Available memory (MB): 16168
  Available CPU cores: 8
Binaries:
  Node: 22.19.0
  npm: 10.9.3
  Yarn: 1.22.19
  pnpm: 10.20.0
Relevant Packages:
  next: 16.0.1 // Latest available version is detected (16.0.1).
  eslint-config-next: N/A
  react: 19.2.0
  react-dom: 19.2.0
  typescript: 5.9.3
Next.js Config:
  output: N/A
Done in 3.06s.
Which area(s) are affected? (Select all that apply)

Not sure

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

next build (local)

Additional context

No response

Contributor guide

Open the contributing guide

First steps

  1. Read the whole issue, then the project's contributing guide.
  2. Comment on the issue to say you are picking it up — it saves two people doing the same work.
  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

Research direction

Start with the linked md2docx examples/nextjs reproduction, install dependencies, and run its build command under Next.js 16.0.1. Compare the failing /_not-found prerender with Next.js 15; done means the reproduction builds without the reported function-passing error.

Written by the indexing model from the issue text.

Assessment

Tech stack
javascript, next.js, react, typescript
Domain
build-system, frontend, web-dev
Issue type
Bug
Difficulty
3/5
Estimated time
1-2 days
Activity status
Stale
Clarity
Mostly clear
Newbie friendliness
35/100

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