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Turbopack 16.3: Nft.Json Drops Store Target Files For An ESM ServerExternalPackage Reached Via A 'Use Client' Component In A Shared SSR-Layer Chunk → Dangling Alias → ERR_MODULE_NOT_FOUND On Vercel

In Next.js 16.3 with Turbopack, when an externalized server package is referenced only from a shared SSR-layer chunk (generated for 'use client' components), routes that do not import the package can have the package's content-hashed alias symlink in their .nft.json but not the corresponding store target files. This causes Vercel to pack a dangling symlink, leading to ERR_MODULE_NOT_FOUND and HTTP 500 on affected routes.

highConfidence 90%Next.js Affected V16.3.0-Preview.6 Affected V16.3.0-Canary.86

Origin Analysis

The endpoint file tracer for nft.json includes the alias symlink for a shared SSR chunk because the chunk's specifier string physically contains the alias, but it only traces the store target files for packages present in the endpoint's own module graph. For a shared SSR chunk referenced by endpoints that do not import the package, the alias is collected without its resolved store target, producing a broken trace.

1. Create a Next.js 16.3 app with Turbopack and `serverExternalPackages` including a package like `@ai-sdk/google`. 2. Import the package transitively through a `'use client'` component that gets bundled into a shared SSR-layer chunk, ensuring another route (e.g. auth page) does not import the package but shares the chunk. 3. Run `next build` with a package manager using an isolated linker (e.g. bun). 4. Inspect the `.nft.json` of the non-importing route: it contains the package's content-hashed alias symlink but no store target files. 5. Deploy to Vercel: the route fails with `ERR_MODULE_NOT_FOUND`.

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

The script adds the entire resolved package directory to the nft trace, which may increase deployment size and include unnecessary files (source maps, test files). It relies on Node.js `fs.realpathSync` and recursive directory walking; on Windows, path separators are normalized for nft. It should be run after `next build` and before deployment; remove the script and revert nft files to rollback. Test thoroughly across platforms and package managers, especially with pnpm/yarn PnP layouts. This is a temporary workaround until the upstream tracer is fixed.