aleqsio/react-native-worktree/skill

react-native-worktree — Multi-Agent Worktree Guide

You are an AI agent working on a React Native / Expo project alongside other agents. Each agent works in its own git worktree with its own Metro server. Only one agent can use the device/simulator at a time per platform. react-native-worktree handles port switching and runtime coordination.

Creating a Worktree (Lightweight)

Git worktrees share the .git object store, so they're cheap — but you should still exclude heavy generated directories that each worktree can regenerate on its own.

Expo projects with Continuous Native Generation (CNG)

If ios/ and android/ are in .gitignore (standard for CNG projects), worktrees are already lightweight — those dirs won't be copied. Just create normally:

git worktree add ../my-feature -b my-feature

Projects with tracked native directories

If ios/ and android/ are tracked in git, use sparse checkout to skip them:

# Create worktree without checking out files
git worktree add --no-checkout ../my-feature -b my-feature
 
# Configure sparse checkout to exclude native dirs
cd ../my-feature
git sparse-checkout set --no-cone '/*' '!ios/' '!android/'
git checkout

This saves significant disk space and creation time. The agent can run npx expo prebuild later if it specifically needs native files.

Always exclude node_modules

node_modules/ is gitignored and never copied by worktrees. Each worktree needs its own install:

cd ../my-feature
npm install   # or: yarn / bun install

Registering and Using react-native-worktree

Registering your worktree

On first run, add auto-detects the bundle ID and platforms from app.json / app.config.js and creates the config automatically. No separate init step needed.

react-native-worktree add my-feature --path /path/to/my-feature
# Output: Added 'my-feature' on port 8083 (app: com.myapp)
# Output: Start Metro: cd /path/to/my-feature && npx expo start --port 8083

The port is auto-assigned. If a previously registered worktree's Metro is dead, its port is reclaimed and the stale worktree entry is removed from config.

IMPORTANT: Start Metro immediately after `add`, before registering any other worktrees. Port reclamation detects dead Metro servers — if you register multiple worktrees without starting Metro, they may all get the same port. Always do add then start sequentially for each worktree:

react-native-worktree add my-feature --path /path/to/my-feature
cd /path/to/my-feature
npx expo start --port 8083    # start BEFORE adding the next worktree

If Metro reports "port busy", re-run add with the same worktree name — it will reassign a new available port:

react-native-worktree add my-feature --path /path/to/my-feature
# got port 8082, but Metro says it's busy:
# Error: port 8082 already in use
react-native-worktree add my-feature --path /path/to/my-feature   # re-add → gets port 8083
npx expo start --port 8083

Multi-app projects

If you have multiple apps configured, specify which one:

react-native-worktree add my-feature --app com.myapp --path /path/to/my-feature

If only one app is configured, --app is auto-detected.

Switching the device to your worktree

react-native-worktree switch my-feature                    # uses first configured platform
react-native-worktree switch my-feature --platform ios     # explicit platform
react-native-worktree switch my-feature --platform android # independent Android lock

This does three things atomically:

1. Acquires the mutex lock for that platform (waits if another agent holds it)
2. Reconfigures the device to connect to your Metro port
3. Kills and relaunches the app

iOS and Android locks are independent — one agent can hold the iOS lock while another holds Android. If another agent holds the lock for your platform, the command blocks and prints Waiting for 'other-agent' to release... until the lock is freed or goes stale.

The --timeout flag controls the inactivity threshold — how long a lock can sit without a heartbeat before another agent can reclaim it. It does NOT limit how long the waiting agent will poll.

Heartbeat — keeping the lock alive

While you are actively using the device, periodically call switch again:

react-native-worktree switch my-feature --platform ios   # refreshes timestamp, no app restart

This updates the lock timestamp so other agents know you're still active. If you stop calling, the lock goes stale after 60s and another agent can take over.

Releasing the device

When done testing:

react-native-worktree release --platform ios
react-native-worktree release --platform android

Always release when you're finished so other agents don't have to wait for the stale timeout. Each platform is released independently.

Checking status

react-native-worktree status                    # all platform locks
react-native-worktree status --platform ios      # just iOS
react-native-worktree list                       # all apps and worktrees
react-native-worktree list --app com.myapp       # filter by app

Typical Agent Workflow

# 1. Create worktree, register, and start Metro (do these sequentially — don't add another worktree until Metro is running)
git worktree add ../feat-auth -b feat-auth
cd ../feat-auth
npm install
react-native-worktree add feat-auth --path $(pwd)
# note the assigned port from output
npx expo start --port <assigned-port>   # start Metro IMMEDIATELY after add
 
# 2. When you need the device to preview your work
react-native-worktree switch feat-auth --platform ios
# device restarts connected to your Metro
 
# 4. Keep the lock alive while user is testing
react-native-worktree switch feat-auth --platform ios   # heartbeat every ~20s
 
# 5. Release when done
react-native-worktree release --platform ios
 
# 6. Clean up when branch is merged
cd /path/to/main
git worktree remove ../feat-auth

CRITICAL: Lock Before Any Device Operation

You MUST call `react-native-worktree switch <name> --platform <platform>` and hold the lock BEFORE any operation that touches the simulator or emulator. This includes:

• Taking screenshots of the app
• Reading simulator/emulator logs
• Running xcrun simctl commands
• Running adb commands against the device
• Any UI testing or visual inspection
• Launching or restarting the app

If you do not hold the lock, another agent may switch the device out from under you at any moment, causing your operation to hit the wrong app state or fail entirely. Always acquire first, then interact with the device.

Important Rules

• Never use Expo Go. Always build and use the actual development client with the correct bundle ID. Expo Go does not support RCT_jsLocation switching or custom native modules. Only use Expo Go if the user explicitly asks for it.
• Build and install the app if needed. If the app is not already installed on the simulator/emulator, build and install it first:
• iOS: npx expo run:ios (builds with the correct bundle ID and installs on the simulator)
• Android: npx expo run:android (builds with the correct package name and installs on the emulator)
• Only one worktree needs to build — the binary is shared across all worktrees since only the Metro port changes.
• Lock before touching the device. Every xcrun simctl, adb, screenshot, or log read requires you to hold the lock for that platform. No exceptions.
• Always release the lock when you're done with the device. Don't hog it.
• Start Metro before switching. react-native-worktree switch warns if Metro isn't running on your port, but it still acquires the lock.
• Don't force-take the lock. If another agent holds it, wait. The mutex exists to prevent app thrashing.
• Heartbeat if holding long. If you hold the lock for more than a few seconds, call switch again periodically to avoid the inactivity timeout (default 60s).
• One port per worktree. Don't change ports after registration. Other agents rely on the mapping.
• `--timeout` is the inactivity threshold, not a wait limit. It controls how long a lock survives without heartbeats. The waiting agent polls forever until the lock is free.
• iOS and Android are independent. You can hold both platform locks simultaneously if needed, and two different agents can hold different platform locks at the same time.
• Port reuse is automatic. When adding a worktree without --port, dead Metro ports are reclaimed. You don't need to manage port numbers manually.