nextjs - 💡(How to fix) Fix Turbopack dev on macOS hits Watchpack fs.watch EMFILE on ancestor directories and app subtrees [1 comments, 2 participants]

Title: Turbopack dev on macOS hits Watchpack fs.watch EMFILE on ancestor directories and app subtrees

Summary

On macOS, Next.js 16.2.3 Turbopack development mode is hitting repeated native fs.watch EMFILE errors even with a very high shell file-descriptor limit. The failure appears in Watchpack, triggers false next.config.js restarts, and can destabilize the dev server.

Version

Next.js 16.2.3

Link to the code that reproduces this issue

https://github.com/wzrdgang/next-turbopack-emfile-macos-repro

To Reproduce

1. On macOS, clone the repro repo.
2. Run npm install
3. Run npm run dev:debug
4. Observe repeated Watchpack Error (watcher): Error: EMFILE: too many open files, watch
5. Observe the debug watcher targets printed by the fs.watch preload in scripts/watch-debug.cjs

Current vs. Expected behavior

Current behavior:

• Turbopack dev starts, then immediately emits repeated Watchpack EMFILE errors
• The debug logger shows fs.watch EMFILE events for ancestor directories like:
  • /Users
  • /Users/<user>
  • /Users/<user>/Documents/...
  • the project root
  • multiple app/... subdirectories
• The same run also triggers false Found a change in next.config.js. Restarting the server to apply the changes...

Expected behavior:

• next dev with Turbopack should watch only the needed project paths without entering an EMFILE loop
• A high ulimit -n should not still result in repeated native watcher failures
• Turbopack should not restart because of false-positive config change detection during watcher failure

Environment

• OS: macOS 15.7.4
• Kernel: Darwin 24.6.0 arm64
• Node versions tested:
  • 25.9.0
  • 24.14.0
• npm: 11.12.1
• ulimit -n: 1048575

Additional context

• The repro intentionally creates a moderately wide App Router tree under app/ because the larger real-world app showed the same failure pattern
• The failure reproduced with both Node 25.9.0 and Node 24.14.0
• The repro still succeeds with npm run build, so the problem appears isolated to Turbopack dev watchers
• A validated watcher-target excerpt is included in VALIDATED_WATCH_LOG.txt
• In the larger Munimetric app, the same logger also showed native watch attempts on /Users, /Users/samhowell, /Users/samhowell/Documents, /Users/samhowell/Documents/munimetric, /Users/samhowell/Documents/munimetric/frontend, /Users/samhowell/Documents/munimetric/frontend/app, and many frontend/app/... route directories
• In the larger app, webpack + polling works around the issue, but that bypasses Turbopack instead of fixing it

Validated watcher-target excerpt

[fs.watch EMFILE event] /private
[fs.watch EMFILE event] /private/tmp
[fs.watch EMFILE event] /private/tmp/next-turbopack-emfile-macos-repro
[fs.watch EMFILE event] /private/tmp/next-turbopack-emfile-macos-repro/app
[fs.watch EMFILE event] /private/tmp/next-turbopack-emfile-macos-repro/app/about
[fs.watch EMFILE event] /private/tmp/next-turbopack-emfile-macos-repro/app/api
[fs.watch EMFILE event] /private/tmp/next-turbopack-emfile-macos-repro/app/internal
[fs.watch EMFILE event] /private/tmp/next-turbopack-emfile-macos-repro/app/states
Watchpack Error (watcher): Error: EMFILE: too many open files, watch
⚠ Found a change in next.config.js. Restarting the server to apply the changes...