TypeError: Could not find package '__sveltekit' from referrer

[janosh]

Describe the bug

vitest started failing after #13971 was shipped in v2.22.3

TypeError: Could not find package '__sveltekit' from referrer 'file:///home/runner/work/matterviz/matterviz/node_modules/.deno/@sveltejs+kit@2.22.3/node_modules/@sveltejs/kit/src/runtime/client/client.js'.
 ❯ src/lib/periodic-table/PeriodicTable.svelte:4:31
 ❯ src/lib/periodic-table/index.ts:3:1

⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯
Serialized Error: { code: 'ERR_MODULE_NOT_FOUND' }

Reproduction

run npm install && npm test in https://stackblitz.com/edit/sveltejs-kit-template-default-4x24ccgf

Logs

System Info

System:
    OS: macOS 15.5
    CPU: (14) arm64 Apple M4 Pro
    Memory: 141.50 MB / 24.00 GB
    Shell: 5.9 - /bin/zsh
  Binaries:
    Node: 24.2.0 - /opt/homebrew/bin/node
    npm: 11.3.0 - /opt/homebrew/bin/npm
    pnpm: 10.11.0 - /opt/homebrew/bin/pnpm
  Browsers:
    Brave Browser: 138.1.80.115
    Safari: 18.5

Severity

serious, but I can work around it

Additional Information

No response

[Rich-Harris]

The heart of the issue appears to be that $app/navigation and similar modules aren't being processed by Vite when run via vitest — they're being loaded as-is direct from the filesystem. I don't yet know why, and I don't know why #13971 would have changed it

[Rich-Harris]

Trawling through the Vitest codebase, I see this — Vitest apparently has its own logic for determining which modules should be externalized, which it seems doesn't perfectly match Vite's. The $app/* modules are externalized because they resolve to files inside node_modules. Trying to understand how to force it to bundle them instead

[Rich-Harris]

#13977 appears to fix it:

pnpm i https://pkg.pr.new/sveltejs/kit/@sveltejs/kit@dd5f2c1 

Or at least, the error I get running pnpm test is the same as I get with 2.22.2