Windows: pnpm self-update from the bootstrap leaves a pnpm.cmd shim that is not recognized (pnpm 11 to 12) #291

Summary

On windows-latest, with pnpm/action-setup@v6.1.0 and a packageManager of pnpm@12.11.2, every PowerShell step that calls pnpm after setup fails. The shim pnpm resolves to points at a path that does not run:

'"C:\Users\runneradmin\setup-pnpm\node_modules\.bin\bin\\..\global\v11\<id>\node_modules\pnpm\pnpm"' is not recognized as an internal or external command,

Bash steps on the same runner still work, because they resolve pnpm to the extensionless script rather than the .cmd shim.

What I see in the logs

The action bootstraps pnpm 11 (src/install-pnpm/run.ts) and then runs pnpm self-update <version> to the version in packageManager. The log line is Switching pnpm from v11.7.0 to v12.11.2. On Windows the .cmd shim left by that self-update points at the v11 global layout (global\v11) with the path quoted and the bin\ segment doubled, and the shim does not start.

The same workflow passes on Linux and macOS, and passes on Windows when packageManager is pnpm@11.x (main), so the trigger seems to be the pnpm 11 to 12 self-update on Windows.

Evidence

• Failing run (Windows native job, pwsh step pnpm exec vitest run ... and pnpm install --frozen-lockfile): https://github.com/visulima/visulima/actions/runs/38249468484
• Same error from a pnpm install step under PowerShell in run https://github.com/visulima/visulima/actions/runs/38249468484 (job 114818869468).

Not verified

I have not reduced this to a minimal repro outside our repository, and I have not checked whether pnpm 12.12.x changes the shim. I don't know whether the fault is in the action's self-update step or in pnpm's shim writer.

Environment

• pnpm/action-setup@v6.1.0 (pinned by anolilab/workflows/step/node at aa162a98)
• windows-latest, Node 24
• packageManager: pnpm@12.11.2