Branch switch times out after 10 seconds in large repos and leaves the working tree half-switched #22245

What happened

I switched branches with the branch picker in a large monorepo. The switch failed after about 10 seconds. The old branch was still checked out, but the working tree showed 3,918 deleted files, 2,241 modified files and 50 untracked files from the target branch.

It happened twice. The first time I didn't notice, and my next git pull --autostash stashed the broken tree and then conflicted when applying it back.

Diagnosis

switchRef runs git checkout with a fixed 10-second timeout:

In this repo, switching between the two branches rewrites about 6,000 files, some through Git LFS, so the checkout takes longer than 10 seconds. The timeout kills git after it has written part of the target branch's files, but before it updates the index and HEAD. Git can't roll back an interrupted checkout, so the working tree is left mixed and the UI shows only a generic failure.

Long-running commands such as push already pass timeoutMs: null (L2660). Checkout changes the working tree, so killing it partway does more damage than letting it finish. Running it without a timeout, or warning that the working tree may be partially updated when it fails, would avoid this.

Steps to reproduce

1. Open a repo where switching between two branches rewrites enough files that git checkout takes more than 10 seconds (here about 6,000 files, with Git LFS).
2. Switch to the other branch with the branch picker.
3. After about 10 seconds the switch fails. git status shows thousands of changes and the old branch is still checked out.

Running the same git checkout <branch> in a terminal completes normally.

Version

0.1.1-nightly.20261019.3348

Environment

Windows desktop app, server in WSL2 (Ubuntu 24.04.4), git 2.43.0, git-lfs 3.4.1

Evidence

server.trace.ndjson:
GitVcsDriver.switchRef.checkout  durationMs=10025.5  2026-10-20 11:45:32
GitVcsDriver.switchRef.checkout  durationMs=10028.8  2026-10-20 12:06:23
GitCommandError: Git command failed in GitVcsDriver.switchRef.checkout (<repo>): Git command timed out.
cause: InterruptError: All fibers interrupted without error
    at runGitCommand

git status --short | cut -c1-2 | sort | uniq -c   (after the second failure)
   3918  D
   2241  M
     50 ??

Related issues

#15541 hits the fixed 5-minute git timeout during worktree creation. It's the same kind of problem, but a different code path and limit, so a fix there wouldn't cover branch switching.

Fix applied or workaround

Restored the old branch with git reset --hard HEAD and git clean -fd, then ran git checkout from a terminal, which completed.

Filed by

Claude Code (claude-opus-5-5) in a T3 Code thread