MetricKit Reference

Complete API reference for collecting field performance metrics and diagnostics using MetricKit. Covers metric payloads, diagnostic payloads, call stack symbolication, and integration patterns.

When to Use This Reference

Use this reference when:

• Setting up an MXMetricManagerSubscriber in your app
• Parsing MXMetricPayload for CPU, memory, launch, or disk I/O metrics
• Parsing MXDiagnosticPayload for crash, hang, and exception diagnostics
• Symbolicating MXCallStackTree frames with dSYMs
• Understanding background exit reasons (jetsam, watchdog, CPU limit)
• Integrating MetricKit alongside a crash reporter like Crashlytics or Sentry

Example Prompts

Questions you can ask Claude that will draw from this reference:

• "How do I set up MetricKit to collect crash data?"
• "How do I symbolicate MetricKit call stacks?"
• "What background exit types does MetricKit track?"
• "How do I parse MXDiagnosticPayload for hang diagnostics?"
• "How do I use MetricKit signpost metrics for custom operations?"
• "What's the difference between MetricKit and Xcode Organizer?"

What's Covered

• MXMetricManagerSubscriber setup and registration timing
• MXMetricPayload: CPU, memory, launch time histograms, disk I/O, network, scroll hitches, signpost metrics
• MXDiagnosticPayload: crash, hang, disk write exception, and CPU exception diagnostics
• MXCallStackTree JSON parsing and symbolication with atos
• MXBackgroundExitData: all 10 exit types with interpretation and recommended actions
• Integration patterns: analytics upload, hybrid crash reporting, regression alerting
• MetricKit vs Xcode Organizer comparison
• Common gotchas: 24-hour delay, opt-in only, simulator limitations, unsymbolicated stacks

Documentation Scope

This page documents the axiom-metrickit-ref reference skill -- the complete MetricKit API guide Claude uses when you need to collect and analyze field performance data.

For profiling during development: See xctrace-ref for CLI-based Instruments profiling.

For App Store Connect metrics: See app-store-connect-ref for the web dashboard view of performance data.

For hang diagnosis: See the axiom-hang-diagnostics skill for hang-specific workflows.

Related

• app-store-connect-ref -- Web dashboard crash and metrics analysis
• xctrace-ref -- CLI Instruments profiling for development

Resources

WWDC: 2019-417, 2020-10081, 2021-10087

Docs: /metrickit, /metrickit/mxmetricmanager, /metrickit/mxdiagnosticpayload