Thread resumes in a worktree folder without .git instead of recreating the checkout #24390

What happened

Earlier storage-cleanup removals on Windows left the worktree folder in place with only node_modules (sometimes .next) inside, with no .git and no tracked files. When a thread pointing at such a folder runs again, T3 Code sees that the folder exists and skips checkout recovery, so the agent works in a directory with no checkout.

Expected: a managed worktree path that is not a valid checkout is recovered (cleared and recreated from the thread's branch), the same way a missing folder is.

Diagnosis

• On this machine, 75 folders under ~\.t3\worktrees\<project>\ were in this state. Most were removed in bursts on 2026-10-16 and 2026-10-21 on 0.1.1. Their node_modules are pnpm layouts full of NTFS junctions. With Git for Windows ≥ 2.54, git worktree remove skips junctions and leaves them and their parent folders behind, which is exactly what apps/server/src/vcs/worktreeRemoval.ts describes. fix(server): removing a worktree on Windows no longer deletes what its junctions point to #21099 fixed the removal for new cleanups, but nothing repairs folders that are already broken.
• apps/server/src/orchestration-v2/ProviderTurnStartService.ts:476-480 (v0.1.2; same on main at ~491-493) recreates the worktree only when !fileSystem.exists(worktreePath). A folder holding only node_modules passes the existence check, so pruneWorktrees + createWorktree never run.
• The same folders also make every storage-cleanup sweep log a failure. storageCleanup.ts:803 calls fs.stat(path.join(worktreePath, ".git")), which throws ENOENT instead of returning keep("not a linked worktree"). In the retained traces, the same thread failed this way at 10:47 and 11:48 (hourly).

Suggested direction: in ProviderTurnStartService, treat a managed worktree path without a valid .git link (or one not registered in git worktree list) like a missing one. In storageCleanup.ts, handle a missing .git as a "kept" outcome, not an error.

Steps to reproduce

Deterministic, without depending on Git's junction behaviour:

1. Create a worktree thread in a pnpm project and let setup install node_modules.
2. Stop the thread, then delete everything in the worktree folder except node_modules (including the .git file). Optionally run git worktree prune in the main repo.
3. Send a new message to the thread.
4. Expected: "provider turn start recreating missing worktree" and a fresh checkout of the thread's branch. Actual (from source): the existence check passes, recovery is skipped, and the turn runs in the gutted folder.
5. Separately, the next storage-cleanup sweep logs "storage cleanup failed for worktree" with NotFound … stat …\.git.

Natural repro on 0.1.1: Windows, Git for Windows ≥ 2.54, pnpm project, and any worktree cleanup rule removing the worktree.

Version

0.1.2 (recovery gap and sweep error; also on main). The leftover folders themselves were created on 0.1.1.

Environment

Windows 11 (10.0.26200) x64, Node v26.12.1, Git 2.55.0.windows.3, pnpm projects, desktop app with local server

Evidence

# leftover folder (one of 75)
~\.t3\worktrees\zesty-explorer\t3code-df890ade\   contents: node_modules\   (no .git; mtime 2026-10-16 11:35)
node_modules\clsx  Junction -> ...\t3code-df890ade\node_modules\.pnpm\clsx@2.1.1\node_modules\clsx

# server.trace.ndjson, StorageCleanup.cleanWorktrees, 2026-10-24 10:47 and 11:48
"storage cleanup failed for worktree", threadId 6ba3d897-8d26-4c66-b75a-17d412d03866
  reason: { _tag: "NotFound", module: "FileSystem", method: "stat",
            pathOrDescriptor: "~\\.t3\\worktrees\\zesty-explorer\\t3code-df890ade\\.git" }

Related issues

#21374 covers a missing worktree directory where the re-create fails with branch_checked_out_in_worktree; this report is the case where the directory still exists, so re-create never starts. #19124 is about turns failing after merge removes the worktree and branch. #21099 (PR) fixed how the folders get left behind, not recovery from them.

Fix applied or workaround

With the user's approval, deleted the 75 folders whose only top-level entries were node_modules/.next and that had no .git. Deletion used Node's fs.rmSync, which unlinks junctions without following them; no junction pointed outside its own folder. Threads using those paths should now go through the normal missing-worktree recreation. Folders with any other content were left alone.

Filed by

Claude Code (Claude Opus 5.5, claude-opus-5-5) via t3 triage