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Output File Tracing Silently Discards Dependency-Resolution Failures, Causing Standalone Deployments To 500 Or Drop Metadata

When Next.js standalone output is built with Turbopack (or webpack), output file tracing may fail to resolve a dependency but only records the failure in internal warnings that are never surfaced. The resulting .nft.json contains only the package.json of the broken dependency, so runtime require() fails with a deep internal module path. Build exits 0, leading to 500s or silently missing metadata in production.

highConfidence 85%Next.js Affected V16.2.9 Affected V16.3.1-Canary.3

Origin Analysis

Output file tracing (via @vercel/nft for webpack or turbopack-nft for Turbopack) records dependency-resolution failures in warnings/reasons, but the build step only consumes the file list and ignores warnings. For lazy-loaded external packages (e.g., jsdom on serverExternalPackages), the tracing emits a bare package.json without its entry file, so Node's exports map later resolves to a non-existent path at runtime.

1. Create a Next.js app with output: 'standalone' and a route that lazily imports jsdom (or any package on serverExternalPackages with a transitive dependency on lru-cache). 2. Run npm install. 3. Delete the file resolved by lru-cache's exports map under Node conditions, e.g.: rm node_modules/lru-cache/dist/commonjs/node/index.min.js 4. Run npx next build (uses Turbopack). Build exits 0 with no warnings. 5. Deploy the standalone output or run node .next/standalone/server.js. 6. Request the route; observe HTTP 500 or HTTP 200 with missing metadata.

Fixing Code Block

0x7F 45 4C 46 02 01 01 000x90 12 AB 04 C1 7E 33 08
0xA4 1C 90 3E 77 0B D2 580x11 F6 6A 2C 80 19 DE 44
0x00 00 00 00 03 00 3E 000x01 00 B7 4D 55 90 0C 61
0x6C 69 62 63 2E 73 6F 2E0x36 00 8E 17 42 AA 05 F3
0xDE C0 DE 01 8B 45 FC 890xC7 5D 20 6F 91 03 E4 78
0x13 37 00 4F 9A 2D E1 700x08 B4 5C 22 71 D0 4A 16
0x48 8D 3D 22 01 00 00 E80x91 FF 0A 63 2E 57 B8 04
0x5A 91 C3 0E 44 70 1B 880x02 6F 39 C4 15 80 ED 27
0xFF 15 40 20 60 00 48 890xC3 90 7A 01 4C 28 B1 56
0x0F 1F 44 00 00 55 48 890xE5 C3 18 6D 92 0B 33 A7

Edge Case Audit

This fix only addresses the webpack tracing path; the Turbopack path (used in the repro) remains silent and would require a separate Rust-side change to route tracing failures through the issues system. Enabling NEXT_STRICT_NFT=1 may break builds that currently have benign optional dependency warnings (e.g., optional peer dependencies), so use it only in CI where such warnings are acceptable to fail. The console.warn logging may be noisy for large projects; consider gating detailed per-warning output behind a debug flag while keeping the summary always visible. Rollback: remove the patch or unset NEXT_STRICT_NFT.