claude-code - 💡(How to fix) Fix [Bug] Agent isolation: "worktree" flag ignored for concurrent background agents [2 comments, 3 participants]

Bug Description

Title: Agent tool's isolation: "worktree" flag silently ignored for concurrent background agents

Summary

The Agent tool accepts isolation: "worktree", documented as "creates a temporary git worktree so the agent works on an
isolated copy of the repo." When launching 3 concurrent background agents with this flag, no worktrees were created — all three agents ran in the shared main working tree and clobbered each other's uncommitted files via concurrent branch
switches.

Repro

1. From a branch with some existing state, launch 3+ agents in a single message:
   Agent({ subagent_type: "general-purpose",
   isolation: "worktree",
   run_in_background: true, prompt: "git checkout -b test-<N> origin/main, write some new files, build, commit, push, open PR"
   })
2. Let them run concurrently.

Expected: each agent gets its own worktree under .claude/worktrees/<something>. Main working tree and other agents' trees remain untouched.

Actual:

• task-notification result includes worktreePath: /path/to/repo/.claude/worktrees/null (literal string "null") for every agent.
• No worktrees appear in git worktree list that correspond to the agents.
• All agents operate on the shared main working tree. When one runs git checkout -b …, it switches the branch for all;
  uncommitted/untracked files from the other agents get stashed, lost, or reverted.
• Multiple agents independently reported: "a concurrent /batch agent clobbered the main repo working tree mid-run,
  dropping my first set of file writes." … Note: Content was truncated.