aio-ios-device-debug

name	aio-ios-device-debug
description	Debug iOS apps on physical devices from the terminal — deploy to iPhone or iPad with xcodebuild, capture syslog via idevicesyslog, pull crash reports from the device, analyze .ips crash files, and take device screenshots. Covers the full loop: build, install, launch, capture syslog, pull crash report, analyze .ips crash file, and grab a device screenshot. Uses libimobiledevice (idevicesyslog, idevicecrashreport) and pymobiledevice3 for iOS 17+ compatibility. Use when debugging an iOS app on a physical device, deploying to iPhone without the Xcode GUI, troubleshooting a crash from a .ips file, or capturing a device screenshot over USB.
when_to_use	debug on device, deploy to iPhone, get crash logs, pull crash report, device screenshot, syslog, iOS device, physical device, libimobiledevice, idevicesyslog, idevicecrashreport, xcodebuild, analyze ips crash file, capture syslog, xcodebuild device, debug iOS app on physical device
argument-hint	[build | logs | crash | screenshot] [optional bundle id]
effort	medium

SCRIPTS="${CLAUDE_PLUGIN_ROOT}/skills/aio-ios-device-debug/scripts"

iOS Device Debug

Environment

• xcode-select: !xcode-select -p 2>/dev/null || echo "NOT INSTALLED"
• idevicesyslog: !which idevicesyslog 2>/dev/null || echo "NOT INSTALLED — brew install libimobiledevice"
• idevicecrashreport: !which idevicecrashreport 2>/dev/null || echo "NOT INSTALLED — brew install libimobiledevice"
• python3: !which python3 2>/dev/null || echo "NOT INSTALLED"
• pymobiledevice3: !python3 -c "import pymobiledevice3" 2>/dev/null && echo "installed" || echo "NOT INSTALLED — pip3 install pymobiledevice3"
• Connected devices: !idevice_id -l 2>/dev/null || echo "none detected (or idevice_id missing)"

Debug iOS apps on physical devices: build, install, launch, capture logs, pull crash reports, and analyze crashes — all from the terminal without Xcode GUI.

Prerequisites

Required tools (check before starting):

• Xcode with command line tools (xcode-select --install)
• libimobiledevice: brew install libimobiledevice (provides idevicesyslog, idevicecrashreport)
• pymobiledevice3: pip3 install pymobiledevice3 (required for screenshots on iOS 17+)
• Python 3: for crash report parsing and pymobiledevice3
• Physical iOS device connected via USB or WiFi

Workflow Overview

The debug workflow follows this sequence:

1. Discover device — find device ID
2. Build & install — compile and deploy to device
3. Launch & capture logs — run app while recording syslog
4. Check for crash — search logs for Corpse/signal
5. Pull crash reports — extract .ips files from device
6. Analyze crash — parse .ips for stack trace and root cause

Scripts

Script	Purpose
$SCRIPTS/device-list.sh	List connected devices with both devicectl and xcodebuild IDs
$SCRIPTS/build-install.sh	Build scheme and install on device
$SCRIPTS/launch-and-log.sh	Launch app, capture syslog, check for crashes
$SCRIPTS/pull-crash-reports.sh	Pull .ips crash reports from device
$SCRIPTS/analyze-crash.sh	Parse .ips file into human-readable analysis
$SCRIPTS/screenshot.sh	Capture screenshot from device (iOS 17+ compatible)

Step-by-Step Debug Process

1. Discover Device

Two ID systems exist for iOS devices — xcodebuild and devicectl use different IDs:

# Get xcodebuild device ID (needed for build/install)
xcodebuild -scheme <Scheme> -showdestinations 2>/dev/null | grep "platform:iOS," | grep -v Simulator

# Get devicectl UUID (needed for devicectl commands)
xcrun devicectl list devices

The xcodebuild ID (e.g., 00008140-...) is used for building and installing. The devicectl UUID is different. Always verify which ID a command expects.

Capture Screenshot

On iOS 17+, idevicescreenshot and the deprecated pymobiledevice3 developer screenshot API both fail. Use the DVT screenshot method via pymobiledevice3 tunnel instead.

Prerequisites:

1. Install pymobiledevice3: pip3 install pymobiledevice3
2. Start tunneld (requires sudo, run once in background):

   sudo python3 -m pymobiledevice3 remote tunneld -p tcp
   

3. Developer image must be mounted (usually already done if Xcode has connected to the device):

   python3 -m pymobiledevice3 mounter auto-mount
   

Capture screenshot:

# Using the script (recommended)
bash $SCRIPTS/screenshot.sh /tmp/device_screenshot.png

# Manual command
python3 -m pymobiledevice3 developer dvt screenshot --tunnel "" /tmp/device_screenshot.png

The --tunnel "" flag auto-discovers the device through the running tunneld service.

What does NOT work on iOS 17+:

Method	Status	Error
idevicescreenshot	FAILS	"Could not start screenshotr service: Invalid service"
pymobiledevice3 developer screenshot	FAILS	"InvalidServiceError" (deprecated API)
pymobiledevice3 developer screenshot --tunnel ""	FAILS	deprecated API, same error through tunnel
xcrun devicectl	N/A	No screenshot subcommand exists
pymobiledevice3 developer dvt screenshot --tunnel ""	WORKS	DVT API through tunneld

2. Build & Install

# Build for device
xcodebuild -scheme <Scheme> -destination 'platform=iOS,id=<DEVICE_ID>' -allowProvisioningUpdates build

# Find the .app
find ~/Library/Developer/Xcode/DerivedData -path "*/<Scheme>-*/Build/Products/Debug-iphoneos/<Scheme>.app" -maxdepth 5

# Install
xcrun devicectl device install app --device <DEVICECTL_UUID> /path/to/App.app

Or use the combined script:

bash $SCRIPTS/build-install.sh <Scheme> <XCODEBUILD_DEVICE_ID>

3. Launch & Capture Logs

Start syslog capture BEFORE launching the app to catch early crashes:

# Start syslog in background, writing to file
idevicesyslog --no-colors > /tmp/app_syslog.txt 2>&1 &
SYSLOG_PID=$!
sleep 3  # Wait for connection

# Launch app
xcrun devicectl device process launch --device <DEVICECTL_UUID> <BUNDLE_ID>

# Wait for crash or behavior
sleep 20

# Stop syslog
kill $SYSLOG_PID

Or use the combined script:

bash $SCRIPTS/launch-and-log.sh <BUNDLE_ID> <DEVICECTL_UUID> 20

4. Analyze Logs

After capturing, filter for relevant information:

# Find app PID
grep -oE 'AppName\[[0-9]+\]' /tmp/app_syslog.txt | sort -u

# Check for crash (Corpse = kernel generating crash report)
grep "Corpse" /tmp/app_syslog.txt

# Find crash signal
grep -E "Process exited.*signal" /tmp/app_syslog.txt
# Example output: code:SIGTRAP(5) = Swift runtime trap
# Example output: code:SIGABRT(6) = abort/exception

# Filter app-only logs
grep "AppName\[PID\]" /tmp/app_syslog.txt | grep -v "CoreFoundation\|BaseBoard"

5. Pull & Analyze Crash Reports

# Pull all crash reports from device
mkdir -p /tmp/crashes
idevicecrashreport -e /tmp/crashes/

# Find app-specific crashes
ls /tmp/crashes/ | grep -i AppName

# Analyze the latest crash
bash $SCRIPTS/analyze-crash.sh /tmp/crashes/AppName-2026-02-09-173322.ips

The analyze script outputs: exception type, signal, faulting thread, stack trace with app frames highlighted, and a diagnosis based on the signal type.

Key Signals and What They Mean

Signal	Exception	Meaning
SIGTRAP	EXC_BREAKPOINT	Swift runtime trap: force unwrap nil, precondition, actor isolation violation
SIGABRT	EXC_CRASH	Abort: uncaught exception, fatalError(), assertion
SIGSEGV	EXC_BAD_ACCESS	Bad memory: use-after-free, null pointer, dangling pointer
SIGKILL	—	System kill: watchdog timeout, OOM (jetsam), background time exceeded

Common Pitfalls

• Wrong device ID: xcodebuild and devicectl use DIFFERENT IDs. Do not mix them.
• Screenshot on iOS 17+: idevicescreenshot and the deprecated pymobiledevice3 screenshot API do NOT work. You MUST use pymobiledevice3 developer dvt screenshot --tunnel "". Requires tunneld running with sudo python3 -m pymobiledevice3 remote tunneld -p tcp.
• Syslog disconnects: idevicesyslog can disconnect. Always verify logs were captured (check file size).
• Benign CoreMotion warning: Error reading com.apple.CoreMotion.plist is a system log, not an app error.
• Swift 6 actor isolation: dispatch_assert_queue_fail in stack = closure running on wrong queue for @MainActor class. Fix with @Sendable annotation.
• Process filter: idevicesyslog -p <bundle_id> can be too aggressive. Prefer capturing all logs to a file and filtering with grep afterward.

Additional Resources

Reference Files

• references/crash-patterns.md — Detailed crash signal patterns, Swift 6 concurrency crashes, CoreMotion/CoreLocation issues, device ID systems, log filtering recipes