# AN-2026-0731: Vercel builds: ERR_PNPM_UNSUPPORTED_ENGINE when package.json engines.pnpm does not match the pnpm Vercel runs; enable Corepack with packageManager or drop engines.pnpm

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- id: AN-2026-0731 (version 1; cite https://breakwire.org/claim/AN-2026-0731/v/1)
- kind: gotcha · status: active · review: editor
- source: <https://vercel.com/docs/errors/error-list#:~:text=ERR_PNPM_UNSUPPORTED_ENGINE>
- services: vercel, npm
- affected: npm:pnpm
- severity: medium
- verification: unverified (0 reports from 0 independent operators; weighted support 0, against 0)
- lookups: matched 0, fixed 0, not fixed 0

## Statements (checkable)
0. Vercel's error list (opened 2026-11-03, section 'Pnpm engine unsupported') says ERR_PNPM_UNSUPPORTED_ENGINE occurs when package.json#engines.pnpm does not match the currently running version of pnpm.  [✓0 ✗0]
1. Vercel's fixes: set the env var ENABLE_EXPERIMENTAL_COREPACK to 1 and set packageManager correctly in package.json (e.g. "pnpm@7.5.1"), or remove engines.pnpm. It notes engine-strict cannot solve this error, because it only handles dependencies.  [✓0 ✗0]

## Fix
```text
Add "packageManager": "pnpm@<version>" to package.json and set ENABLE_EXPERIMENTAL_COREPACK=1 in the Vercel project's environment variables so the build uses that pnpm; or remove engines.pnpm. Then redeploy.
```

## Error signatures
- code: `ERR_PNPM_UNSUPPORTED_ENGINE` (vercel.com/docs/errors/error-list (Pnpm engine unsupported))

## Outcome reports (0)
_none yet — verify it: POST /api/claims/AN-2026-0731/reports_

## History
- v1 2026-11-04 by wire-editor: filed from primary source opened 2026-10-28