nextjs - 💡(How to fix) Fix Turbopack build: NFT warning "unexpected file" / next.config in trace with server routes reading fs outside app/ (outputFileTracingRoot) [1 comments, 2 participants]

Description

During next build (Turbopack, Next.js 16.2.x), the build succeeds but prints:

Encountered unexpected file in NFT list for ./app/next.config.ts, with an import trace such as:

next.config.ts → src/lib/records.ts → src/app/api/records/route.ts

The message suggests "whole project traced unintentionally" and mentions path.join / fs.readFile.

Setup (minimal shape)

• Monorepo or repo layout where the Next app lives in app/ and shared content (e.g. markdown DB) lives next to app/ at the repo root, e.g. knowledge-base/app/ and knowledge-base/db/**/*.md.
• next.config.ts under app/ sets:
  • outputFileTracingRoot: path.join(__dirname, '..') (parent = repo root that contains db/)
  • outputFileTracingIncludes with globs like db/**/*.md relative to that root.
• Server-only code uses fs + path.join(process.cwd(), '..', 'db', ...) (with turbopackIgnore on process.cwd() where applicable) to read markdown at runtime.

Actual behavior

Warning appears every production build. It does not fail the build.

Expected / question

• Is this warning safe to ignore when outputFileTracingIncludes and deploy traces are correct?
• Or should Turbopack stop associating next.config with route modules in this graph, or downgrade the diagnostic when outputFileTracingRoot intentionally points outside app/?

What we tried (still warns or worse)

• /* turbopackIgnore: true */ on __dirname in path.join for outputFileTracingRoot — warning remains.
• next build --webpack — warning gone, but NFT manifests did not list db/**/*.md the same way; deployment trace checks failed.
• turbopack.root — not used; known to cause other resolution issues in monorepos (see existing discussions).

Environment

• Next.js: 16.2.2
• Node: 22.x (example)
• OS: Windows / Linux (repro on Windows with repo under Dropbox path)

Reference

Public repo for full layout (if maintainers want a real tree): https://github.com/alawein/knowledge-base — build: cd app && npm run build; post-build NFT check: npm run verify:nft in app/.