Console Capture (xclog)

Reference for xclog, an iOS console capture tool that unifies print()/debugPrint() output with os_log/Logger into structured JSON — designed for LLM consumption. Supports both simulator and physical devices.

When to Use This Reference

Use this reference when:

• You need to see what an app is printing to the console
• Diagnosing runtime crashes (need logs leading up to the crash)
• Investigating silent failures (network, data, auth) with no UI feedback
• Capturing structured simulator logs for automated analysis

Core problem solved: No single external tool replicates Xcode's debug console. xclog combines simctl launch --console (captures print) with log stream --style json (captures os_log) into a single unified stream.

Example Prompts

• "Show me what my app is logging"
• "Capture the simulator console while I reproduce this crash"
• "My app fails silently — I need to see the logs"
• "xclog to my usual simulator"

What This Skill Provides

• list / launch / attach / show command reference with all flags
• JSON output schema with level, subsystem, category, process, pid fields
• Crash diagnosis workflow — list → launch with bounded capture → reproduce → filter errors
• Silent failure workflow — subsystem-filtered capture
• Coverage table — which Swift APIs are captured in each mode
• Error behavior — common error messages and fixes

Key Concepts

• launch mode captures everything (print + os_log) but restarts the app (simulator only)
• attach mode preserves app state but only captures os_log (simulator only)
• show mode searches recent logs post-mortem — works with simulator AND physical devices
• JSON is the default output format — no flags needed for structured output
• Always run list first to discover the correct bundle ID
• Always bound output with --timeout and --max-lines to protect context

Related

• Xcode Debugging — environment-first diagnostics (xclog is for runtime, xcode-debugging is for build-time)
• Performance Profiling — capture logs before profiling to understand what to measure
• LLDB Debugging — xclog captures logs, LLDB inspects live state
• /axiom:console — guided capture command