Link to the code that reproduces this issue

https://github.com/snelusha/nextjs-16-config-wrapper-issue

To Reproduce

1. Start the application in development (next dev)
2. Observe that withContentCollections wrapper does not execute
3. Stop the server with Ctrl+C and the wrapper will execute during shutdown

Current vs. Expected behavior

Current Behavior:

When I run next dev in Next.js 16.0.0-beta, the development server starts successfully, but the withContentCollections config wrapper never executes during startup. The content collections are not processed, so the application runs without them. Only when I stop the server using Ctrl+C does the withContentCollections wrapper finally execute - it processes the content collections and starts watching for changes, but the server is already shutting down at this point.

Note: The config wrapper works as expected when running next build - it only fails during next dev.

Expected Behavior:

The withContentCollections config wrapper should execute immediately when next dev starts, before the server becomes available. Content collections should be processed during the startup phase and the wrapper should start watching for changes while the server is running. This is how it worked correctly in Next.js 15.x - the wrapper would run first, process content, watch for changes, and then the dev server would be ready.

Provide environment information

Operating System:
  Platform: linux
  Arch: x64
  Version: #1 SMP PREEMPT_DYNAMIC Thu Jun  5 18:30:46 UTC 2025
  Available memory (MB): 7741
  Available CPU cores: 8
Binaries:
  Node: 22.17.0
  npm: 10.9.2
  Yarn: N/A
  pnpm: 10.14.0
  bun: 1.2.22
Relevant Packages:
  next: 16.0.0-beta.0 // Latest available version is detected (16.0.0-beta.0).
  eslint-config-next: 16.0.0-beta.0
  react: 19.1.0
  react-dom: 19.1.0
  typescript: 5.9.3
Next.js Config:
  output: N/A

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

Not sure

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

next dev (local)

Additional context

This issue is a regression - the same configuration works correctly in Next.js 15.x.

The config wrapper pattern is commonly used by many Next.js plugins and build-time tools (like MDX processors, content management systems, etc.), so this likely affects other similar packages that wrap the Next.js config, not just @content-collections/next. (not sure)

Workaround: Downgrading to Next.js 15.x resolves the issue.