Use when starting feature work that needs isolation from current workspace or before executing implementation plans - ensures an isolated workspace exists via native tools or git worktree fallback
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Use when starting feature work that needs isolation from current workspace or before executing implementation plans - ensures an isolated workspace exists via native tools or git worktree fallback
Using Git Worktrees
Overview
Ensure work happens in an isolated workspace. Prefer your platform's native worktree tools. Fall back to manual git worktrees only when no native tool is available.
Core principle: Detect existing isolation first. Then use native tools. Then fall back to git. Never fight the harness.
Announce at start: "I'm using the compose:worktree skill to set up an isolated workspace."
Step 0: Detect Existing Isolation
Before creating anything, check if you are already in an isolated workspace.
Submodule guard:GIT_DIR != GIT_COMMON is also true inside git submodules. Before concluding "already in a worktree," verify you are not in a submodule:
# If this returns a path, you're in a submodule, not a worktree — treat as normal repo
git rev-parse --show-superproject-working-tree 2>/dev/null
If GIT_DIR != GIT_COMMON (and not a submodule): You are already in a linked worktree. Skip to Step 3 (Project Setup). Do NOT create another worktree.
Report with branch state:
On a branch: "Already in isolated workspace at <path> on branch <name>."
Detached HEAD: "Already in isolated workspace at <path> (detached HEAD, externally managed). Branch creation needed at finish time."
If GIT_DIR == GIT_COMMON (or in a submodule): You are in a normal repo checkout.
Check memory for a worktree-consent preference in the compose-preferences memory file, or check your instructions for a declared worktree preference. If either exists, honor it silently.
If no saved preference, use compose:ask:
header: Worktree
question: Set up an isolated worktree? It protects your current branch from changes.
options:
label: Yes (Recommended), description: Create an isolated worktree for this work
label: No, description: Work directly on the current branch
label: Always use worktrees, description: Use worktrees now and remember for future sessions
label: Never use worktrees, description: Work in place now and remember for future sessions
If no user is available, create the worktree and proceed.
If "Always" or "Never": Save to the compose-preferences memory file as worktree-consent: always or worktree-consent: never.
If the user declined (chose "No" or "Never"), work in place and skip to Step 3.
Step 1: Create Isolated Workspace
You have two mechanisms. Try them in this order.
1a. Native Worktree Tools (preferred)
The user has asked for an isolated workspace (Step 0 consent). Do you already have a way to create a worktree? It might be a tool with a name like EnterWorktree, WorktreeCreate, a /worktree command, or a --worktree flag. If you do, use it and skip to Step 3.
Native tools handle directory placement, branch creation, and cleanup automatically. Using git worktree add when you have a native tool creates phantom state your harness can't see or manage.
Only proceed to Step 1b if you have no native worktree tool available.
1b. Git Worktree Fallback
Only use this if Step 1a does not apply — you have no native worktree tool available. Create a worktree manually using git.
Directory Selection
Follow this priority order. Explicit user preference always beats observed filesystem state.
Check your instructions for a declared worktree directory preference. If the user has already specified one, use it without asking.
Check for an existing project-local worktree directory:
ls -d .worktrees 2>/dev/null # Preferred (hidden)ls -d worktrees 2>/dev/null # Alternative
If found, use it. If both exist, .worktrees wins.
Check for an existing global directory:
project=$(basename"$(git rev-parse --show-toplevel)")
ls -d ~/.config/compose/worktrees/$project 2>/dev/null
If found, use it (backward compatibility with legacy global path).
If there is no other guidance available, default to .worktrees/ at the project root.
If NOT ignored: Add to .gitignore, commit the change, then proceed.
Why critical: Prevents accidentally committing worktree contents to repository.
Global directories (~/.config/compose/worktrees/) need no verification.
Create the Worktree
project=$(basename"$(git rev-parse --show-toplevel)")
# Determine path based on chosen location# For project-local: path="$LOCATION/$BRANCH_NAME"# For global: path="~/.config/compose/worktrees/$project/$BRANCH_NAME"
git worktree add "$path" -b "$BRANCH_NAME"cd"$path"
Sandbox fallback: If git worktree add fails with a permission error (sandbox denial), tell the user the sandbox blocked worktree creation and you're working in the current directory instead. Then run setup and baseline tests in place.
Step 3: Project Setup
Auto-detect and run appropriate setup:
# Node.jsif [ -f package.json ]; then npm install; fi# Rustif [ -f Cargo.toml ]; then cargo build; fi# Pythonif [ -f requirements.txt ]; then pip install -r requirements.txt; fiif [ -f pyproject.toml ]; then poetry install; fi# Goif [ -f go.mod ]; then go mod download; fi
Step 4: Verify Clean Baseline
Run tests to ensure workspace starts clean:
# Use project-appropriate command
npm test / cargo test / pytest / go test ./...
If tests fail: Report failures, then use compose:ask:
header: Baseline Tests
question: Baseline tests have <N> failures (pre-existing, not caused by your changes).
options:
label: Proceed anyway (Recommended), description: Start working — failures existed before this branch
label: Investigate first, description: Debug test failures before starting
If no user is available, proceed with the failing tests.
If tests pass: Report ready.
Report
Worktree ready at <full-path>
Tests passing (<N> tests, 0 failures)
Ready to implement <feature-name>
Quick Reference
Situation
Action
Already in linked worktree
Skip creation (Step 0)
In a submodule
Treat as normal repo (Step 0 guard)
Native worktree tool available
Use it (Step 1a)
No native tool
Git worktree fallback (Step 1b)
.worktrees/ exists
Use it (verify ignored)
worktrees/ exists
Use it (verify ignored)
Both exist
Use .worktrees/
Neither exists
Check instruction file, then default .worktrees/
Global path exists
Use it (backward compat)
Directory not ignored
Add to .gitignore + commit
Permission error on create
Sandbox fallback, work in place
Tests fail during baseline
Report failures + ask
No package.json/Cargo.toml
Skip dependency install
Common Mistakes
Fighting the harness
Problem: Using git worktree add when the platform already provides isolation
