[Bug]: Each dev worktree costs ~160 MB and ~372k files; deleting one takes minutes #26926

Before submitting

• I searched existing issues and did not find a duplicate.
• I included enough detail to reproduce or investigate the problem.

Area

Build, CI, or release tooling

Steps to reproduce

1. On macOS (APFS), check out this repo into many git worktrees, as agent threads do (one worktree per thread).
2. Run the normal worktree setup (vp i) in each, with the default per-project pnpm virtual store.
3. Measure the physical disk use per worktree on an isolated volume, then rm -rf node_modules.

Expected behavior

Additional dev worktrees should cost little disk and be cheap to delete, since the package files are already in pnpm's content-addressed store.

Actual behavior

Measured on macOS (APFS), warm store, one worktree each, on an isolated APFS volume so other writes couldn't skew it:

The global store itself is a one-time ~7.6 GB. du reports ~6–7 GB per per-project worktree because APFS clones are counted per copy. The physical cost is the ~160 MB above, plus ~372k files of metadata that every delete has to walk.

Impact

Major degradation or frequent failure

Version or commit

main (e6ca170)

Environment

macOS 27, APFS, pnpm 11.28.6 for the comparison. With ~100 agent worktrees on one machine, that's ~15 GB of disk and minutes of delete I/O per cleanup, and the disk fills during multi-agent work.

Logs or stack traces

No response

Screenshots, recordings, or supporting files

#22765 tried an opt-in global virtual store and was closed because pnpm 12 took most of the install-speed win; disk and delete time weren't part of that decision. Proposal and discussion: #26925

Workaround

Our fork runs pnpm's virtualStoreType: global unconditionally, CI included, so type resolution can't differ from CI. Vite, Metro and desktop packaging follow the store links through one shared helper. Happy to send a focused PR if maintainers want it.