---
name: worktree-agent
promoted_to: do
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.

## Rule 10: Reserve disk capacity before creating a checkout

The dispatcher runs this before each implementation worktree:

```bash
python3 ~/.claude/skills/process/worktree-agent/scripts/worktree_capacity.py \
  --repo "$(git rev-parse --show-toplevel)" --strict
```

The JSON report has three states:

| State | Dispatcher action |
|---|---|
| `ready` (<80% used) | Create the one implementation checkout for the candidate. |
| `cleanup-soon` (80–<85%) | Reclaim accepted clean checkouts before adding another. Use root read-only review work where possible. |
| `blocked` (≥85%) | Integrate, deploy, verify, or reclaim; create no new checkout. |

The report lists clean candidates only. The dispatcher confirms their task is inactive before removal because Git cleanliness alone does not prove that fact.

## Rule 11: Assign checkout roles deliberately

| Task | Checkout policy |
|---|---|
| Source implementation or repair | One writable task worktree, reused through review corrections. |
| Code review, test-plan review, or read-only investigation | Read the candidate through `git diff` or `git show` from the repository root; allocate no checkout. |
| Large repository implementation | Create a sparse worktree containing declared source/test/config scopes; include whole-repository content only when the task requires it. |

For a sparse implementation checkout:

```bash
git worktree add --no-checkout <worktree-path> -b <branch> <base-sha>
git -C <worktree-path> sparse-checkout init --no-cone
git -C <worktree-path> sparse-checkout set --no-cone <declared-path>...
git -C <worktree-path> checkout
```

Record any full-checkout reason in the dispatch handoff.

## Post-Merge Cleanup

After integration or a PR merge, the dispatcher first confirms that the task is inactive and the checkout is clean, then runs:

```bash
git worktree remove -- <accepted-worktree-path>
bash scripts/worktree-cleanup.sh --force
```

`git worktree remove` frees the materialized checkout while preserving its branch for recovery. The cleanup script then prunes stale `.git/worktrees` entries and removes merged harness branches.

## 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 |