iOS Simulator Skill

Build, test, and automate iOS applications using accessibility-driven navigation and structured data instead of pixel coordinates.

Quick Start

# 1. Check environment
bash scripts/sim_health_check.sh

# 2. Launch app
python scripts/app_launcher.py --launch com.example.app

# 3. Map screen to see elements
python scripts/screen_mapper.py

# 4. Tap button
python scripts/navigator.py --find-text "Login" --tap

# 5. Enter text
python scripts/navigator.py --find-type TextField --enter-text "user@example.com"

All scripts support --help for detailed options and --json for machine-readable output.

Navigation Strategy

Always prefer the accessibility tree over screenshots for navigation. The accessibility tree gives you element types, labels, frames, and tap targets — structured data that's cheaper and more reliable than image analysis.

Use this priority:

1. screen_mapper.py → structured element list (5-7 lines, ~10 tokens)
2. navigator.py --find-text/--find-type/--find-id → semantic interaction
3. Screenshots → only for visual verification, bug reports, or visual diff

Screenshots cost 1,600–6,300 tokens depending on size. The accessibility tree costs 10–50 tokens in default mode.

29 Production Scripts

Build & Development (2 scripts)

1. build_and_test.py - Build Xcode projects, run tests, parse results with progressive disclosure

   • Build with live result streaming
   • Parse errors and warnings from xcresult bundles
   • Retrieve detailed build logs on demand
   • Options: --project, --scheme, --clean, --test, --verbose, --json

2. log_monitor.py - Real-time log monitoring with intelligent filtering

   • Stream logs or capture by duration
   • Filter by severity (error/warning/info/debug)
   • Deduplicate repeated messages
   • Options: --app, --severity, --follow, --duration, --output, --json

Device State (2 scripts)

3. appearance.py - Control simulator appearance: dark mode, Dynamic Type size, and locale/region

   • Toggle light/dark theme via xcrun simctl ui
   • Set Dynamic Type size with friendly aliases (XS through AX5)
   • Write locale and region defaults; optional app restart via --bundle-id
   • RTL flagged automatically for ar/he/fa/ur/yi locales
   • Options: --theme, --text-size, --locale, --region, --reset, --bundle-id, --udid, --json, --verbose

4. location.py - Simulate GPS coordinates, named city presets, and GPX scenario playback

   • Fix a coordinate with --lat/--lng or pick a city with --city
   • Play a built-in scenario (City Run, Freeway Drive, etc.) via --gpx <scenario>
   • Animate multi-waypoint paths with configurable speed via --waypoints and --speed
   • Clear simulated location with --clear; list available scenarios with --list-scenarios
   • Options: --lat, --lng, --city, --gpx, --waypoints, --speed, --clear, --list-scenarios, --udid, --json, --verbose

Navigation & Interaction (5 scripts)

5. screen_mapper.py - Analyze current screen and list interactive elements

   • Element type breakdown
   • Interactive button list
   • Text field status
   • Options: --verbose, --hints, --json

6. navigator.py - Find and interact with elements semantically

   • Find by text (fuzzy matching)
   • Find by element type
   • Find by accessibility ID
   • Enter text or tap elements
   • Options: --find-text, --find-type, --find-id, --tap, --enter-text, --json

7. gesture.py - Perform swipes, scrolls, pinches, and complex gestures

   • Directional swipes (up/down/left/right)
   • Multi-swipe scrolling
   • Pinch zoom
   • Long press
   • Pull to refresh
   • Options: --swipe, --scroll, --pinch, --long-press, --refresh, --json

8. keyboard.py - Text input and hardware button control

   • Type text (fast or slow)
   • Special keys (return, delete, tab, space, arrows)
   • Hardware buttons (home, lock, volume, screenshot)
   • Key combinations
   • Options: --type, --key, --button, --slow, --clear, --dismiss, --json

9. app_launcher.py - App lifecycle management

   • Launch apps by bundle ID
   • Terminate apps
   • Install/uninstall from .app bundles
   • Deep link navigation
   • List installed apps
   • Check app state
   • Pass launch arguments (--args) and environment variables (--env KEY=VALUE, injected as SIMCTL_CHILD_*) to the app on launch/restart
   • Options: --launch, --terminate, --restart, --install, --uninstall, --open-url, --list, --state, --args, --env, --wait-for-debugger

Testing & Analysis (9 scripts)

10. accessibility_audit.py - Check WCAG compliance on current screen

    • Critical issues (missing labels, empty buttons, no alt text)
    • Warnings (missing hints, small touch targets)
    • Info (missing IDs, deep nesting)
    • Options: --verbose, --output, --json

11. visual_diff.py - Compare two screenshots for visual changes

    • Pixel-by-pixel comparison
    • Threshold-based pass/fail
    • Generate diff images
    • Options: --threshold, --output, --details, --json

12. test_recorder.py - Automatically document test execution

    • Capture screenshots and accessibility trees per step
    • Generate markdown reports with timing data
    • Options: --test-name, --output, --verbose, --json

13. app_state_capture.py - Create comprehensive debugging snapshots

    • Screenshot, UI hierarchy, app logs, device info
    • Markdown summary for bug reports
    • Options: --app-bundle-id, --output, --log-lines, --json

14. sim_health_check.sh - Verify environment is properly configured

    • Check macOS, Xcode, simctl, IDB, Python
    • List available and booted simulators
    • Verify Python packages (Pillow)

15. model_inspector.py - Inspect Core Data and SwiftData models from project files

    • Parse .xcdatamodeld packages (entities, attributes, relationships)
    • Detect model versions and current active version
    • Best-effort SwiftData @Model class extraction
    • Raw source dump for any model on demand (--raw ModelName)
    • Options: --project-path, --core-data-only, --swiftdata-only, --show-versions, --raw, --verbose, --json

16. container.py - Inspect app sandbox: files, UserDefaults, and Core Data store paths

    • List data container files at configurable depth via --ls
    • Read files with auto-detected plist decoding via --cat (large files cached)
    • Dump UserDefaults as key=value or JSON via --userdefaults
    • Locate .sqlite / .sqlite-wal / .sqlite-shm stores via --core-data-path
    • Export full container snapshot via --export
    • Options: --ls, --cat, --userdefaults, --core-data-path, --export, --udid, --json, --verbose

17. hang_watcher.py (HangBuster) - Record + summarise os_log hang events with progressive disclosure

    • Session mode (HangBuster, agent-native): start a detached recorder, interact with the simulator, stop for a token-tight summary
      • --start → returns a session ID; detached worker normalises + thresholds events on the fly
      • --stop SESSION_ID → emits ~80–120 token L1 summary (header + top-N clusters + drill hint)
      • --get-details SESSION_ID [--cluster N | --raw] → L2 full clusters or L3 per-event detail
      • --list-sessions / --clear-sessions [--older-than 24h] / --diff A B (cross-session regression report)
      • Filter pipeline: parse → normalise → threshold → bucket → cluster → aggregate → rank → format (in common/hang_pipeline.py)
      • --budget-tokens N picks the densest level (L0/L1/L2) that fits; --terse forces L0
      • --auto-sample captures a main-thread stack on first event per cluster (soft dependency: main_thread_sampler.py #62; graceful no-op if absent)
    • Raw capture mode (full fidelity for jq exploration): skip the clustering pipeline, dump every matching log line verbatim to raw.ndjson
      • --start --raw-capture [--max-size-mb 10] [--no-gzip] — spawns log stream --style ndjson
      • Per-session size cap (--max-size-mb, default 10) — worker stops cleanly on cap; extras.truncated=true
      • --stop gzips raw.ndjson → raw.ndjson.gz (~15–19× compression; --no-gzip opts out)
      • --get-details SESSION_ID on a raw session prints the path with a zcat | jq ... hint
    • Resilience (auto-restart on stream death): EOF or subprocess death triggers a stream_died event then a bounded restart with 2s backoff. After IOS_SIM_HANG_MAX_RESTARTS (default 3) the session is marked crashed, never left in stale running state. --list-sessions shows capture=Xs and restarts=N.
    • Cleanup is automatic: TTL prune (IOS_SIM_HANG_SESSION_TTL_HOURS, default 24h) + aggregate cap (IOS_SIM_HANG_TOTAL_CAP_MB, default 100 MB, oldest-first eviction) both run on every --start.
    • Legacy modes (unchanged for backward compat): --watch [--duration N] (live stream) and --since 5m (historical)
    • Filters: --bundle-id (post-parse — hang capture stays simulator-global so RunningBoard/SpringBoard events are kept), --predicate (also via IOS_SIM_HANG_PREDICATE)
    • All output supports --json; session storage at ~/.ios-simulator-skill/sessions/<id>/{meta.json,events.jsonl,summary.json,raw.ndjson.gz}

    Quick start (summarised mode):

    SID=$(python scripts/hang_watcher.py --start --min-hang-ms 200)
    # ... interact with the simulator (open sheets, scroll, navigate) ...
    python scripts/hang_watcher.py --stop $SID                  # token-tight L1 summary
    python scripts/hang_watcher.py --get-details $SID --cluster 1  # drill into cluster 1
    python scripts/hang_watcher.py --diff $SID_BASELINE $SID    # cross-session regression
    

    Quick start (raw capture + jq exploration):

    SID=$(python scripts/hang_watcher.py --start --raw-capture --max-size-mb 5)
    # ... interact with the simulator ...
    python scripts/hang_watcher.py --stop $SID
    # → "Session ...: raw mode, 737 lines, 0.96 MB → 0.05 MB gzipped"
    
    # Top processes by event count:
    zcat ~/.ios-simulator-skill/sessions/$SID/raw.ndjson.gz \
      | jq -s 'group_by(.processImagePath) | map({proc: (.[0].processImagePath | split("/") | last), n: length}) | sort_by(-.n) | .[:5]'
    
    # All RunningBoard assertion invalidations:
    zcat .../raw.ndjson.gz | jq -c 'select(.subsystem == "com.apple.runningboard" and (.eventMessage | startswith("Invalidating")))'
    
    # Hangs per minute:
    zcat .../raw.ndjson.gz | jq -r '.timestamp[:16]' | sort | uniq -c
    

18. localization_audit.py - Detect string catalog gaps, missing keys, and placeholder mismatches

    • Report missing and needs_review/new keys per locale in .xcstrings catalogs
    • Cross-reference catalog keys against Swift source (String(localized:) / NSLocalizedString) via --source
    • Flag placeholder count mismatches (%d, %@, %s, %lld) across locales
    • Legacy .strings and .stringsdict support via plistlib
    • CI-friendly --strict exits 2 on any finding
    • Options: --catalog, --source, --locale, --strict, --json, --verbose

Advanced Testing & Permissions (4 scripts)

19. clipboard.py - Manage simulator clipboard for paste testing

    • Copy text to clipboard
    • Test paste flows without manual entry
    • Options: --copy, --test-name, --expected, --json

20. status_bar.py - Override simulator status bar appearance

    • Presets: clean (9:41, 100% battery), testing (11:11, 50%), low-battery (20%), airplane (offline)
    • Custom time, network, battery, WiFi settings
    • Options: --preset, --time, --data-network, --battery-level, --clear, --json

21. push_notification.py - Send simulated push notifications

    • Simple mode (title + body + badge)
    • Custom JSON payloads
    • Test notification handling and deep links
    • Options: --bundle-id, --title, --body, --badge, --payload, --json

22. privacy_manager.py - Grant, revoke, and reset app permissions

    • 13 supported services (camera, microphone, location, contacts, photos, calendar, health, etc.)
    • Batch operations (comma-separated services)
    • Audit trail with test scenario tracking
    • Options: --bundle-id, --grant, --revoke, --reset, --list, --json

Simulator Discovery (2 scripts)

23. sim_list.py - List simulators with progressive disclosure

    • Concise summary by default (total / available / booted)
    • Full details on demand via cache IDs
    • Filter by device type
    • Suggest recommended simulators with --suggest
    • 96% token reduction vs raw simctl list (57k → 2k tokens)
    • Options: --get-details, --suggest, --device-type, --json

24. simulator_selector.py - Suggest the best simulator for the job

    • Ranks candidates by recent use (from config.json), latest iOS, common test models, and boot status
    • List all available simulators with --list
    • Boot a selected simulator directly with --boot
    • JSON output for programmatic use
    • Options: --suggest, --list, --boot, --json

Device Lifecycle Management (5 scripts)

25. simctl_boot.py - Boot simulators with optional readiness verification

    • Boot by UDID or device name
    • Wait for device ready with timeout
    • Batch boot operations (--all, --type)
    • Performance timing
    • Options: --udid, --name, --wait-ready, --timeout, --all, --type, --json

26. simctl_shutdown.py - Gracefully shutdown simulators

    • Shutdown by UDID or device name
    • Optional verification of shutdown completion
    • Batch shutdown operations
    • Options: --udid, --name, --verify, --timeout, --all, --type, --json

27. simctl_create.py - Create simulators dynamically

    • Create by device type and iOS version
    • List available device types and runtimes
    • Custom device naming
    • Returns UDID for CI/CD integration
    • Options: --device, --runtime, --name, --list-devices, --list-runtimes, --json

28. simctl_delete.py - Permanently delete simulators

    • Delete by UDID or device name
    • Safety confirmation by default (skip with --yes)
    • Batch delete operations
    • Smart deletion (--old N to keep N per device type)
    • Options: --udid, --name, --yes, --all, --type, --old, --json

29. simctl_erase.py - Factory reset simulators without deletion

    • Preserve device UUID (faster than delete+create)
    • Erase all, by type, or booted simulators
    • Optional verification
    • Options: --udid, --name, --verify, --timeout, --all, --type, --booted, --json

Common Patterns

Auto-UDID Detection: Most scripts auto-detect the booted simulator if --udid is not provided.

Device Name Resolution: Use device names (e.g., "iPhone 16 Pro") instead of UDIDs - scripts resolve automatically.

Batch Operations: Many scripts support --all for all simulators or --type iPhone for device type filtering.

Output Formats: Default is concise human-readable output. Use --json for machine-readable output in CI/CD.

Help: All scripts support --help for detailed options and examples.

Screenshot Sizing: Screenshots are resized to save tokens. Presets: full (3-4 tiles, ~5K tokens), half (1 tile, ~1.6K tokens, default), quarter (1 tile, ~800 tokens, less detail). Use quarter for quick visual checks, half for readable UI, full only when pixel-level detail matters. Scripts that capture screenshots (app_state_capture.py, test_recorder.py) default to half.

Typical Workflow

1. Verify environment: bash scripts/sim_health_check.sh
2. Launch app: python scripts/app_launcher.py --launch com.example.app
3. Analyze screen: python scripts/screen_mapper.py
4. Interact: python scripts/navigator.py --find-text "Button" --tap
5. Verify: python scripts/accessibility_audit.py
6. Debug if needed: python scripts/app_state_capture.py --app-bundle-id com.example.app

Configuration

Most operational limits can be tuned via environment variables. Defaults work for typical local development; raise them for slow CI runners, large monorepo builds, or accessibility audits on complex screens.

Variable	Default	Controls
IOS_SIM_A11Y_LABEL_MAX	80	Max chars of AXLabel retained in accessibility audit output
IOS_SIM_A11Y_TOP_ISSUES	10	Top accessibility issues surfaced per audit
IOS_SIM_APPS_PREVIEW	30	App entries listed by app_launcher.py before truncation
IOS_SIM_BOOT_SUBPROCESS_TIMEOUT	60	Timeout for the simctl boot subprocess itself (seconds)
IOS_SIM_BOOT_TIMEOUT	300	Wait-for-ready timeout after boot (seconds)
IOS_SIM_BUILD_JSON_CAP	50	Max build errors / failed tests in JSON output
IOS_SIM_BUILD_LOG_PREVIEW	4000	Chars of build log preview in default output
IOS_SIM_BUILD_TIMEOUT	1800	Max seconds for an xcodebuild build invocation before kill
IOS_SIM_INTROSPECT_TIMEOUT	60	Timeout for xcodebuild -list and simctl list lookups (seconds)
IOS_SIM_TEST_TIMEOUT	2700	Max seconds for an xcodebuild test invocation before kill
IOS_SIM_BUILD_SUMMARY_CAP	15	Errors/failures in default build summary
IOS_SIM_BUILD_VERBOSE_CAP	100	Errors/warnings in verbose build output
IOS_SIM_CACHE_MAX_ENTRIES	500	Max entries in progressive disclosure cache (LRU eviction)
IOS_SIM_CACHE_TTL_HOURS	1	Cache entry expiration
IOS_SIM_ERASE_TIMEOUT	90	Wait-for-erase timeout (seconds)
IOS_SIM_HANG_PREDICATE	(default)	Override the os_log predicate used by hang_watcher.py (default catches RunningBoard kills + "Hang detected" + main-thread hangs). Hang events originate from system daemons (RunningBoard, SpringBoard) so the predicate stays simulator-global — --bundle-id is applied post-parse, not ANDed in.
IOS_SIM_HANG_MIN_MS	250	HangBuster threshold — events below this duration never reach disk (smaller = more sensitive, larger summaries)
IOS_SIM_HANG_SESSION_TTL_HOURS	24	HangBuster session prune age; pruning runs on every --start
IOS_SIM_HANG_DEFAULT_TOP_N	3	Default top-N clusters in --stop L1 output
IOS_SIM_HANG_BUDGET_TOKENS	(unset)	Default token budget for --stop (picks L0/L1/L2 to fit)
IOS_SIM_HANG_MAX_RESTARTS	3	HangBuster worker: max log stream respawn attempts on EOF/subprocess death before the session is marked crashed
IOS_SIM_HANG_TOTAL_CAP_MB	100	HangBuster aggregate disk cap. When total session-state exceeds this on --start, oldest sessions are dropped first. Set to 0 to disable.
IOS_SIM_LOG_JSON_CAP	100	Max errors/warnings in log_monitor.py JSON output
IOS_SIM_LOG_LINE_MAX	300	Per-line truncation in log summaries
IOS_SIM_LOG_TAIL	200	Lines of log tail in verbose / sample output
IOS_SIM_LOG_TEXT_SUMMARY	15	Errors/warnings shown in text-mode log summary
IOS_SIM_MAX_ELEMENTS	25	Tappable elements listed by navigator.py
IOS_SIM_POLL_INTERVAL	0.5	Boot/erase state polling interval (seconds)
IOS_SIM_RELAUNCH_DELAY_MS	1000	Delay between terminate and re-launch in app_launcher.py
IOS_SIM_SCREEN_BUTTONS_PREVIEW	15	Button names listed by screen_mapper.py
IOS_SIM_SCREEN_SECTION_ITEMS	10	Items per section shown by screen_mapper.py
IOS_SIM_STATE_SUBPROCESS_TIMEOUT	15	Subprocess timeout in app_state_capture.py (seconds)
IOS_SIM_TAP_SETTLE_MS	500	Post-tap settle delay in navigator.py

Example:

# Slow GitHub Actions runner: give boot 10 minutes
IOS_SIM_BOOT_TIMEOUT=600 python scripts/simctl_boot.py --wait-ready

Requirements

• macOS 15 (Sequoia)+
• Xcode 26+ and Command Line Tools
• Python 3.12+
• idb 1.5.1+ - required for every interactive script (tap, swipe, type): brew tap facebook/fb && brew install facebook/fb/idb-companion facebook/fb/idb-cli
• Pillow, for visual diffs only: pip3 install pillow

Verify with bash scripts/sim_health_check.sh (add --json for structured output).

Troubleshooting

Taps, swipes and typing do nothing, but reads work. idb reports success and the screen never changes. On Xcode 27 this means idb-companion is older than 1.5.1: it looks for SimulatorKit.framework at the path Xcode 26 used. Upgrade: brew upgrade facebook/fb/idb-companion.

SimulatorKit is required for HID interactions. Same cause, same fix.

Connection refused or No such file from every idb call. A dead companion is still in idb's registry at /tmp/idb/state, so idb dials a socket nobody is listening on instead of starting a fresh companion. Fix: idb disconnect <udid>.

open -a Simulator fails. Xcode 27 has no Simulator.app; it was replaced by DeviceHub.app in Xcode.app/Contents/Applications/. Boot headlessly instead: xcrun simctl boot <udid>. Note that quitting DeviceHub shuts down the simulator it hosts.

idb: command not found. The companion and the CLI are separate packages; install both (see Requirements). If which -a idb shows more than one, the first on PATH wins.

Documentation

• SKILL.md (this file) - Script reference, requirements, troubleshooting
• README.md - Installation, updating idb, Xcode 27 notes
• CLAUDE.md - Architecture and implementation details

Key Design Principles

Semantic Navigation: Find elements by meaning (text, type, ID) not pixel coordinates. Survives UI changes.

Token Efficiency: Concise default output (3-5 lines) with optional verbose and JSON modes for detailed results.

Accessibility-First: Built on standard accessibility APIs for reliability and compatibility.

Zero Configuration: Works immediately on any macOS with Xcode. No setup required.

Structured Data: Scripts output JSON or formatted text, not raw logs. Easy to parse and integrate.

Auto-Learning: Build system remembers your device preference. Configuration stored per-project.

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Use these scripts directly or let Claude Code invoke them automatically when your request matches the skill description.