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The stash is one stack, shared by every worktree

Problem

Work vanished from one worktree and reappeared in another. The symptoms, in the order they confuse:

  • edits made in one worktree are gone from the working tree, and git stash list does not show them
  • a diff nobody in this worktree wrote appears in git status, touching files this branch never intended to change
  • git stash pop reports a conflict against files the branch has not modified

Nothing is corrupted. refs/stash lives in the shared .git directory, so every worktree of the repo pushes onto and pops from one stack. A bare git stash pop takes whatever is on top, which is whoever stashed most recently — not necessarily this worktree.

Any repo with concurrent sessions is exposed to it, because a second session isolates in a worktree of its own. This repo adds one more source. CLAUDE.md puts branch work in a worktree (worktree new <slug>, under ~/.worktrees/) rather than a checkout, so a branch cannot deploy itself over the machine.

Measured 2026-08-10: three worktrees each ran git stash to take a clean pytest baseline. One popped another's work-in-progress into its own tree, a third found its own edits missing from the stack. No commit was lost, but each rebuilt its changes by hand, and one nearly committed another branch's files.

Solution

Do not use git stash while a second worktree on the same repo is active. There is no worktree-scoped stash; --all, --keep-index and a message do not change which stack is used.

To take a before/after baseline without stashing:

  • git worktree add a throwaway checkout at the base commit and measure there, or
  • measure only the after state and compare against what CI recorded for the base commit

To undo local edits to specific files, git restore -- <paths> — it is worktree-local and touches no shared ref.

If a foreign diff has already landed in the working tree: save it (git diff > /tmp/...) before running git restore, and tell whoever owns those files, because their copy may be the only one left.

Key Learnings

  • refs/stash is shared; HEAD, the index and the working tree are per-worktree. Which git state is shared and which is not is not obvious, and stash is the one that surprises.
  • A bare git stash pop is a race whenever more than one worktree exists. It has no "mine only" mode.
  • git restore is the safe alternative for discarding local changes — no shared ref involved.
  • Reach for a throwaway worktree to measure a baseline, never the stash.
  • The same applies to any tool that stashes on your behalf. pre-commit does, which is what pre-commit-stash-recovery.md records from the single-worktree era.