GitHub issue #79366 in anthropics/claude-code, opened 2026-07-20 by sandopolus, records a report that starting a new session with worktree isolation enabled placed the session inside an existing worktree directory created by a previous session for an unrelated task, with a new branch checked out into the old directory, so the directory name no longer matched the task and leftover files from the previous task could leak into the new task context or pull request.

“Starting a new session (new task, worktree isolation enabled) placed the session inside an **existing** worktree directory that a previous session had created for an unrelated task, instead of creating a fresh worktree.”

“Each new session/task with worktree isolation should get a **fresh** worktree directory named after its own task/branch, created off the default branch.”

“Leftover untracked/ignored files from the previous task can silently leak into the new task's context or PR.”