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[Bug]: New worktrees fail with "Git output exceeded 1000000 bytes" when git worktree add writes over 1 MB

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Assessment

Difficulty
2/5
Estimated time
1-3 hours
Newbie friendliness
75/100
Issue type
Bug
Clarity
Clearly specified
Activity status
Active
Tech stack
git, typescript
Domain
developer-experience, tooling

Research direction

Start in apps/server at src/vcs/GitVcsDriverCore.ts, in createWorktree and its call to executeGitWithStableDiagnostics; compare the output handling with the git pull change in #17376. The issue points to truncation handling and progress callbacks as the area to investigate. Verify that oversized output no longer makes a successful git worktree add fail, and that the worktree is created.

Written by the indexing model from the issue text.

Description

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

apps/server

Steps to reproduce
  1. In any repo, add a post-checkout hook that prints more than 1 MB (git sends hook stdout to its stderr): 
    printf '#!/bin/sh\nhead -c 1100000 /dev/zero | tr "\\0" x\n' > .git/hooks/post-checkout && chmod +x .git/hooks/post-checkout
  2. Start a new-worktree thread for that project, or call delegate_task with isolation: "worktree".

The hook is a stand-in for any large output during checkout. A focused driver test on main (695f5c99) fails the same way.

Expected behavior

If git worktree add succeeds, the worktree is created and the thread starts. T3 only needs the progress lines from this command, not its full output.

Actual behavior

createWorktree runs git worktree add under the default 1 MB per-stream output cap, without appendTruncationMarker (GitVcsDriverCore.ts, createWorktree → executeGitWithStableDiagnostics). Once stderr passes 1 MB, the command fails and git is stopped partway through:

Workspace preparation failed during provision worktree: Git command failed in GitVcsDriver.createWorktree (<repo>): Git output exceeded 1000000 bytes and was truncated.

The failed attempt's t3/… branch is left behind.

We hit this in a repo with about 85,000 tracked files and 12,000 Git LFS objects. Two delegate_task worktree launches started 19 s apart from the same commit; one failed this way after about 230 s, and the other succeeded. Checkout progress (GIT_PROGRESS_DELAY=0) isn't the cause: piped stderr from git worktree add measured about 4.4 KB in that repo. We couldn't identify what went over 1 MB, because the output isn't logged. Anything that writes to git's stderr during checkout counts, including hooks, filter drivers such as git-lfs, and per-file warnings.

Impact

Minor bug or occasional failure

Version or commit

Desktop 0.1.1 (same createWorktree as main @ 695f5c99)

Environment

macOS (Darwin 25.6), Apple git 2.50.1, git-lfs 3.5.1

Logs or stack traces
GitCommandError: Git command failed in GitVcsDriver.createWorktree (…): Git output exceeded 1000000 bytes and was truncated.
 ❯ src/vcs/GitVcsDriverCore.ts:870:21  (collectOutput)
Screenshots, recordings, or supporting files

No response

Workaround

Delegate with isolation: "shared" and create the worktree manually.

Possible fix (suggestion only)

Do what #17376 did for git pull: run worktree add with appendTruncationMarker: true. Oversized output is then cut off instead of failing a checkout git completed, and the exit code still decides success. Progress updates past the cap would also need keepLineCallbacksAfterTruncation. Related: #17358, #25207, #21635.

Dominant language
TypeScript
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Merged PRs (30d)
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