simulator-utils - SKILL.md Agent Skill

name: simulator-utils user-invocable: true description: iOS Simulator utility commands for screenshots, resizing, and common operations. Use these commands when taking simulator screenshots, resizing images for API compatibility, or performing common simulator operations.

Simulator Utilities

Quick reference for iOS Simulator commands. Use these patterns whenever working with simulators.

Screenshot with Auto-Resize (REQUIRED)

ALWAYS use this pattern when taking screenshots to avoid API errors:

# Single command: screenshot + resize
xcrun simctl io booted screenshot /path/to/screenshot.png && sips --resampleHeightWidthMax 1800 /path/to/screenshot.png

Why Resize?

iPhone 17 simulator screenshots exceed 2000px
Claude API rejects images >2000px in multi-image requests
sips --resampleHeightWidthMax 1800 keeps images under limit

Resize Existing Screenshots

# Single file
sips --resampleHeightWidthMax 1800 /path/to/screenshot.png

# Multiple files
sips --resampleHeightWidthMax 1800 /path/to/*.png

# Batch resize all PNGs in directory
for f in /path/to/dir/*.png; do sips --resampleHeightWidthMax 1800 "$f"; done

Common Simulator Commands

Device Management

# List available simulators
xcrun simctl list devices available

# Boot specific device (prefer iPhone 17)
xcrun simctl boot "iPhone 17"

# Shutdown simulator
xcrun simctl shutdown booted

# Erase simulator (fresh state)
xcrun simctl erase "iPhone 17"

# Check booted device
xcrun simctl list devices | grep Booted

App Operations

# Install app
xcrun simctl install booted /path/to/App.app

# Launch app
xcrun simctl launch booted com.bundle.identifier

# Terminate app
xcrun simctl terminate booted com.bundle.identifier

# Uninstall app
xcrun simctl uninstall booted com.bundle.identifier

Screenshots

# Basic screenshot (NOT recommended - use resize pattern above)
xcrun simctl io booted screenshot /path/to/screenshot.png

# Screenshot with resize (RECOMMENDED)
xcrun simctl io booted screenshot /path/to/screenshot.png && sips --resampleHeightWidthMax 1800 /path/to/screenshot.png

# Screenshot to clipboard
xcrun simctl io booted screenshot - | pbcopy

Video Recording

# Start recording
xcrun simctl io booted recordVideo /path/to/video.mov

# Stop recording: Ctrl+C

Build Commands

# Build for simulator
xcodebuild -scheme SCHEME -project /path/to/Project.xcodeproj -destination 'platform=iOS Simulator,name=iPhone 17' build

# Build with output filtering (cleaner)
xcodebuild -scheme SCHEME -project /path/to/Project.xcodeproj -destination 'platform=iOS Simulator,name=iPhone 17' build 2>&1 | grep -E "(error:|warning:|BUILD)"

# Find built .app path
find ~/Library/Developer/Xcode/DerivedData -name "*.app" -path "*/Debug-iphonesimulator/*" -type d 2>/dev/null | head -1

Full Test Workflow

Complete pattern for build, install, launch, screenshot:

# 1. Build
xcodebuild -scheme SCHEME -project /path/to/Project.xcodeproj -destination 'platform=iOS Simulator,name=iPhone 17' build 2>&1 | grep -E "(error:|BUILD)"

# 2. Terminate existing instance (ignore errors)
xcrun simctl terminate booted com.bundle.identifier 2>/dev/null

# 3. Install
xcrun simctl install booted "/path/to/App.app"

# 4. Launch
xcrun simctl launch booted com.bundle.identifier

# 5. Wait for app to load
sleep 2

# 6. Screenshot with resize
xcrun simctl io booted screenshot /path/to/screenshot.png && sips --resampleHeightWidthMax 1800 /path/to/screenshot.png

Image Manipulation with sips

sips (Scriptable Image Processing System) is macOS built-in:

# Resize to max dimension (maintains aspect ratio)
sips --resampleHeightWidthMax 1800 image.png

# Resize to specific width
sips --resampleWidth 1000 image.png

# Resize to specific height
sips --resampleHeight 1000 image.png

# Get image dimensions
sips -g pixelWidth -g pixelHeight image.png

# Convert format
sips -s format jpeg image.png --out image.jpg

# Batch resize
sips --resampleHeightWidthMax 1800 *.png

Troubleshooting

"No devices are booted"

xcrun simctl boot "iPhone 17"

Screenshot too large for API

sips --resampleHeightWidthMax 1800 /path/to/screenshot.png

App won't launch

# Check bundle ID
xcrun simctl listapps booted | grep -A5 "CFBundleIdentifier"

# Reinstall
xcrun simctl uninstall booted com.bundle.identifier
xcrun simctl install booted /path/to/App.app

Simulator stuck

xcrun simctl shutdown all
xcrun simctl erase all
xcrun simctl boot "iPhone 17"