iOS Simulator Skill for Claude Code

Production-ready skill for building, testing, and automating iOS apps. 27 scripts optimized for both human developers and AI agents.

(If you'd prefer an MCP, XC-MCP)

Xcode Build + Simulator Automation

This skill covers both sides of iOS development:

• Xcode builds via xcodebuild — compile, test, and parse results with progressive error disclosure
• Simulator interaction via xcrun simctl and idb — semantic UI navigation, accessibility testing, device lifecycle

If you only need Xcode build tooling without the simulator scripts, see the plugin version: xclaude-plugin

Installation

Via Plugin Marketplace (Recommended)

In Claude Code:

/plugin marketplace add conorluddy/ios-simulator-skill
/plugin install ios-simulator-skill@conorluddy

Via Git Clone

# Personal installation
git clone https://github.com/conorluddy/ios-simulator-skill.git ~/.claude/skills/ios-simulator-skill

# Project installation
git clone https://github.com/conorluddy/ios-simulator-skill.git .claude/skills/ios-simulator-skill

Restart Claude Code. The skill loads automatically.

Prerequisites

• macOS 12+
• Xcode Command Line Tools (xcode-select --install)
• Python 3
• IDB (optional, for interactive features: brew tap facebook/fb && brew install idb-companion)
• Pillow (optional, for visual diffs: pip3 install pillow)

Features

Xcode Build with Progressive Disclosure

The build_and_test.py script wraps xcodebuild with token-efficient output. A build returns a single summary line with an xcresult ID:

Build: SUCCESS (0 errors, 3 warnings) [xcresult-20251018-143052]

Then drill into details on demand:

python scripts/build_and_test.py --get-errors xcresult-20251018-143052
python scripts/build_and_test.py --get-warnings xcresult-20251018-143052
python scripts/build_and_test.py --get-log xcresult-20251018-143052

This keeps agent conversations focused — no walls of build output unless you ask for them.

Simulator Navigation via Accessibility

Instead of fragile pixel-coordinate tapping, all navigation uses iOS accessibility APIs to find elements by meaning:

# Fragile — breaks if UI changes
idb ui tap 320 400

# Robust — finds by meaning
python scripts/navigator.py --find-text "Login" --tap

The accessibility tree gives structured data (element types, labels, frames, tap targets) at ~10 tokens default output vs 1,600-6,300 tokens for a screenshot. See AI-Accessible Apps for more on why accessibility-first navigation matters for AI agents.

Screenshot Token Optimization

When screenshots are needed (visual verification, bug reports, diffs), the skill automatically resizes and compresses them to minimize token cost. Default output across all 27 scripts is 3-5 lines — 96% reduction vs raw tool output.

Task	Raw Tools	This Skill	Savings
Screen analysis	200+ lines	5 lines	97.5%
Find & tap button	100+ lines	1 line	99%
Login flow	400+ lines	15 lines	96%

All 27 Scripts

Every script supports --help and --json. See SKILL.md for the complete reference.

Build & Development

Script	What it does	Key flags
build_and_test.py	Build Xcode projects, run tests, parse xcresult bundles	--project, --scheme, --test, --get-errors, --get-warnings
log_monitor.py	Real-time log monitoring with severity filtering	--app, --severity, --follow, --duration

Device State

Script	What it does	Key flags
appearance.py	Switch dark mode, dynamic type, locale, region	--theme, --text-size, --locale, --region, --reset
location.py	Simulate GPS coordinates and run built-in scenarios	--lat, --lng, --city, --gpx, --list-scenarios, --clear

Navigation & Interaction

Script	What it does	Key flags
screen_mapper.py	Analyze current screen, list interactive elements	--verbose, --hints
navigator.py	Find and interact with elements semantically	--find-text, --find-type, --find-id, --tap, --enter-text
gesture.py	Swipes, scrolls, pinches, long press, pull to refresh	--swipe, --scroll, --pinch, --long-press, --refresh
keyboard.py	Text input and hardware button control	--type, --key, --button, --clear, --dismiss
app_launcher.py	Launch, terminate, install, deep link apps	--launch, --terminate, --install, --open-url, --list

Testing & Analysis

Script	What it does	Key flags
accessibility_audit.py	WCAG compliance checking on current screen	--verbose, --output
visual_diff.py	Compare two screenshots for visual changes	--threshold, --output, --details
test_recorder.py	Automated test documentation with screenshots	--test-name, --output
app_state_capture.py	Debugging snapshots (screenshot, hierarchy, logs)	--app-bundle-id, --output, --log-lines
sim_health_check.sh	Verify environment (Xcode, simctl, IDB, Python)	—
model_inspector.py	Inspect Core Data / SwiftData models from project files	--project-path, --raw, --show-versions
container.py	Inspect app sandbox: list, cat, UserDefaults, Core Data, export	--ls, --cat, --userdefaults, --core-data-path, --export
hang_watcher.py (HangBuster)	Record + summarise os_log hang events with progressive disclosure (session mode + raw NDJSON + legacy stream); auto-restart on stream death, automatic disk-cap cleanup	--start [--raw-capture --max-size-mb N --no-gzip], --stop, --get-details, --list-sessions, --diff, --budget-tokens, --auto-sample (legacy: --watch, --since)
localization_audit.py	Audit .xcstrings catalogs for missing keys, unused keys, placeholder mismatches	--catalog, --source, --strict

Permissions & Environment

Script	What it does	Key flags
clipboard.py	Copy text to simulator clipboard for paste testing	--copy, --test-name
status_bar.py	Override status bar (time, battery, network)	--preset, --time, --battery-level, --clear
push_notification.py	Send simulated push notifications	--bundle-id, --title, --body, --payload
privacy_manager.py	Grant, revoke, reset app permissions (13 services)	--bundle-id, --grant, --revoke, --reset

Device Lifecycle

Script	What it does	Key flags
simctl_boot.py	Boot simulators with readiness verification	--name, --wait-ready, --timeout, --all, --type
simctl_shutdown.py	Gracefully shutdown simulators	--name, --verify, --all, --type
simctl_create.py	Create simulators by device type and OS version	--device, --runtime, --list-devices
simctl_delete.py	Delete simulators with safety confirmation	--name, --yes, --all, --old
simctl_erase.py	Factory reset without deletion	--name, --verify, --all, --booted

Configuration

Every operational limit — timeouts, output caps, polling intervals, cache size, post-action delays — is tunable via an IOS_SIM_* environment variable. Defaults are tuned for local development on Apple Silicon. Raise them on slow CI runners, large monorepos, or accessibility audits over complex screens. Lower them when you need faster failure or tighter token budgets.

There's a universal tradeoff to keep in mind:

• Higher caps / longer timeouts → fewer false failures, more complete diagnostics, more tokens consumed by AI agents and slower failures when something is genuinely broken.
• Lower caps / shorter timeouts → faster feedback, tighter token usage, risk of silently dropped errors or premature timeouts on legitimately slow operations.

Boot & lifecycle timeouts

How long to wait on xcrun simctl operations.

Variable	Default	Tradeoff
IOS_SIM_BOOT_TIMEOUT	300 (s)	Wait for simulator readiness after boot. Lower → faster failure on broken sims. Higher → survives cold-start on slow CI runners (GitHub-hosted macOS can need 4–6 min).
IOS_SIM_BOOT_SUBPROCESS_TIMEOUT	60 (s)	Timeout for the simctl boot call itself (before readiness polling starts). Rarely needs changing; bump only if you see Boot command timed out on resource-starved CI.
IOS_SIM_ERASE_TIMEOUT	90 (s)	Wait for factory-reset verification. Larger simulators (lots of installed apps + data) can need more than the old 30s.
IOS_SIM_POLL_INTERVAL	0.5 (s)	How often to re-check boot/erase state. Lower → more responsive (more CPU). Higher → quieter on slow CI but adds latency to “ready” detection.
IOS_SIM_STATE_SUBPROCESS_TIMEOUT	15 (s)	Per-subprocess timeout in app_state_capture.py. Bump for apps with very large accessibility trees.

Build & test output caps

build_and_test.py returns counts by default and full details via xcresult ID; these caps govern what's surfaced in human/JSON output before progressive disclosure kicks in.

Variable	Default	Tradeoff
IOS_SIM_BUILD_SUMMARY_CAP	15	Errors / failed tests in the default text summary. Lower → terser default output. Higher → less need to chase xcresult IDs for context.
IOS_SIM_BUILD_VERBOSE_CAP	100	Errors / warnings in --verbose mode. Mostly relevant for monorepos or first builds with many fixable warnings.
IOS_SIM_BUILD_JSON_CAP	50	Max errors / failed tests in --json output. Raise for CI dashboards that need exhaustive lists.
IOS_SIM_BUILD_LOG_PREVIEW	4000 (chars)	Chars of build log included in default output. Higher → more context for failures, more tokens.
IOS_SIM_BUILD_TIMEOUT	1800 (s)	Hard cap on a single xcodebuild build invocation. Default of 30 min covers most clean builds of large apps; raise for very large monorepos, lower to fail fast in CI when builds are expected to take seconds. Without this, a hung xcodebuild would block forever.
IOS_SIM_TEST_TIMEOUT	2700 (s)	Hard cap on xcodebuild test. Tests can take significantly longer than builds (45 min default) because of simulator boot + animation delays.
IOS_SIM_INTROSPECT_TIMEOUT	60 (s)	Timeout for xcodebuild -list and xcrun simctl list introspection calls. These should normally complete in <1s; 60s catches Xcode-toolchain hangs without disrupting cold-start.

Log monitor output

log_monitor.py aggregates os_log output; these caps shape both the text summary and the structured JSON.

Variable	Default	Tradeoff
IOS_SIM_LOG_TEXT_SUMMARY	15	Errors / warnings shown in the text summary. The default surfaces enough for most debugging without flooding terminal output.
IOS_SIM_LOG_LINE_MAX	300 (chars)	Per-line truncation. Crash messages with full Swift symbol mangling can exceed 200 chars; raise if you see “…” cutting off the actionable bit.
IOS_SIM_LOG_TAIL	200 (lines)	Recent log lines shown in verbose mode and JSON sample_logs. Also used by xcode log excerpt. Lower for tighter context, higher for richer post-mortems.
IOS_SIM_LOG_JSON_CAP	100	Max errors / warnings in JSON output. Raise if you're piping into a dashboard that needs the full picture.
IOS_SIM_HANG_PREDICATE	(default)	Override the os_log predicate used by hang_watcher.py. The default catches Run