Device Control

The device control skill provides comprehensive reference for controlling simulators and emulators, capturing screenshots, reading UI state, managing permissions, and handling Expo/EAS builds.

When loaded

Activates when Claude encounters tasks involving simulator/emulator interaction: taking screenshots, booting devices, installing apps, reading UI hierarchy, opening deep links, granting permissions, streaming native logs, or managing device settings.

Key Knowledge Areas

iOS Simulator (simctl)

Commands for boot/shutdown, app install/launch/terminate, deep links, screenshots, native log streaming, and permissions. Key recommendations:

• Prefer JPEG screenshots (80ms, 200KB) over PNG (150ms, 800KB)
• Use processImagePath ENDSWITH "/BinaryName" for precise native log filtering
• Use xcrun simctl privacy for permission grants/revokes

Android Emulator (adb)

Commands for device management, deep links, screenshots, UI hierarchy extraction, animation control, native logs, permissions, and locale. Key recommendations:

• Use adb exec-out screencap -p for direct-pipe screenshots (skips device storage round-trip)
• uiautomator dump --compressed provides full structured accessibility tree
• Disable animations before test runs (window, transition, animator scales to 0)

agent-device CLI

Cross-platform unified device interaction that eliminates platform-specific branching:

Task	Tool
List devices	device_list
Screenshot	device_screenshot
UI element tree	device_snapshot (returns @refs)
Tap by text	device_find text="Sign In" action=click
Tap by ref	device_press ref=@e3
Fill input	device_fill ref=@e5 text="hello"
Scroll/swipe	device_swipe direction=up
System back	device_back

Concurrent State Snapshot

scripts/snapshot_state.sh captures screenshot + UI hierarchy simultaneously, cutting state-check time by ~40%.

Benchmark Reference

Operation	Time	Size
iOS screenshot (JPEG)	80ms	200KB
iOS screenshot (PNG)	150ms	800KB
Android screenshot (exec-out)	300ms	800KB
Android UI hierarchy (raw)	300-500ms	15-30KB XML
Android UI hierarchy (parsed)	350-550ms	2-3KB JSON

Expo/EAS Build Integration

Decision table for build workflows:

Situation	Action
App running + Metro connected	Skip, proceed to testing
Metro not running, app missing	expo_ensure_running.sh ios or android
Test a specific EAS build	eas_resolve_artifact.sh then expo_ensure_running.sh --artifact

Troubleshooting

Symptom	Fix
Simulator not booting	xcrun simctl shutdown all && xcrun simctl erase all
adb shows “unauthorized”	Revoke USB debugging, reconnect, tap Allow
Screenshot hangs	Wait for home screen, verify boot completed
uiautomator dump fails	Wake screen with keyevent WAKEUP