worktree-agent git:20260612.868c7a0A

Immutable. This exact content is served forever at /api/v1/blob/d0c12ea609ca15f1.

---
name: worktree-agent
description: "Mandatory rules for agents in git worktree isolation."
user-invocable: false
context: fork
tags: [worktree, isolation, parallel, agent]
routing:
  triggers:
    - "worktree agent"
    - "git worktree"
    - "git worktree rules"
    - "isolated agent"
  category: git-workflow
---

# Worktree Agent Rules

Mandatory rules for any agent dispatched with `isolation: "worktree"`.

## Rule 1: Verify Your Working Directory

On start, run `pwd`. Your path MUST contain `.claude/worktrees/`.
If your CWD is the main repo path, **STOP** and report the error.

## Rule 2: Create Feature Branch First

```bash
git checkout -b <branch-name>
```

Never commit on the default `worktree-agent-*` branch. Create your feature branch FIRST.

If `git checkout -b <branch-name>` fails with "a branch named X already exists":

```bash
# Option A: the branch has no commits beyond main — safe to reset and reuse
git branch -D <branch-name>
git checkout -b <branch-name>

# Option B: the branch is checked out in another active worktree — use a unique name
git checkout -b <branch-name>-2   # or append timestamp: $(date +%s)
```

If `git checkout -b <branch-name>` fails with "X is already used by worktree at Y":

```bash
# Branch is live in another worktree — use a unique suffix
git checkout -b <branch-name>-$(date +%s)
```

To update a branch held by another worktree (e.g. an existing PR branch): work detached from `origin/<branch>` and push with `git push origin HEAD:<branch>`. `gh pr merge`'s post-merge local-checkout errors are harmless.

## Rule 3: Use Worktree-Relative Paths

Never hardcode absolute paths from the main repo. Use `$(git rev-parse --show-toplevel)/path`.
**Exception**: Reading gitignored ADR files requires the main repo absolute path.

## Rule 4: Ignore Auto-Plan Hooks

Keep planning inline instead of creating `task_plan.md`. If the auto-plan hook fires, continue with the current task and keep your attention on implementation.

## Rule 5: Stage Specific Files Only

```bash
git add path/to/specific/file.py
```

Never `git add .`, `git add -A`, or `git add --all`. Verify with `git diff --cached --stat`.

## Rule 6: Do Not Touch the Main Worktree

Never write to paths outside your worktree directory. Never run `git checkout` in the main repo.

## Rule 7: Commit with Conventional Format

Use the commit message specified in your prompt. No attribution lines.

## Rule 8: Run Both ruff Checks Before Declaring CI-Ready

For any Python code changes, run both checks before pushing or creating a PR:

```bash
ruff check . --config pyproject.toml
ruff format --check . --config pyproject.toml
```

Running only `ruff check` misses formatting violations. The `Tests / lint` CI job runs both — if you skip `ruff format --check`, the PR will fail CI and cannot merge due to branch protection.

## Rule 9: Run Preflight Check on Start

Run the preflight script at the start of any worktree task to confirm clean state:

```bash
bash scripts/worktree-preflight.sh <intended-branch-name>
```

If it exits 1, fix the reported issue before proceeding.

## Post-Merge Cleanup

After a PR is merged, the dispatcher runs:

```bash
bash scripts/worktree-cleanup.sh --force
```

This prunes stale `.git/worktrees` entries and deletes zombie branches (harness-created branches with no active worktree that are already merged into main). Run manually when `git worktree list` shows stale locked entries.

## Failure Modes This Prevents

| Failure | Rule | Without It |
|---------|------|-----------|
| Agent edits main repo files | 1, 6 | Changes leak to main, get stashed/lost |
| Context wasted on task_plan.md | 4 | Implementation budget consumed by planning |
| Commit on wrong branch | 2 | Orchestrator merges wrong content |
| PR has changes from 2 ADRs | 5, 6 | Cross-contamination between agents |
| Branch locked by worktree | 2 | Fatal error on checkout |
| PR fails CI on format | 8 | Merge blocked; `ruff format --check` was skipped |
| New task fails to create worktree | 9 | Branch name collision from prior stale run |