iOS Performance Router

You MUST use this skill for ANY performance issue including memory leaks, slow execution, battery drain, or profiling.

When to Use

Use this router when:

• App feels slow or laggy
• Memory usage grows over time
• Battery drains quickly
• Device gets hot during use
• High energy usage in Battery Settings
• Diagnosing performance with Instruments
• Memory leaks or retain cycles
• App crashes with memory warnings

Routing Logic

Memory Issues

Memory leaks (Swift) → /skill axiom-memory-debugging

• Systematic leak diagnosis
• 5 common leak patterns
• Instruments workflows
• deinit not called

Memory leak scan → Launch memory-auditor agent or /axiom:audit memory (6 common patterns: timers, observers, closures, delegates, view callbacks, PhotoKit)

Memory leaks (Objective-C blocks) → /skill axiom-objc-block-retain-cycles

• Block retain cycles
• Weak-strong pattern
• Network callback leaks

Performance Profiling

Performance profiling (GUI) → /skill axiom-performance-profiling

• Time Profiler (CPU)
• Allocations (memory growth)
• Core Data profiling (N+1 queries)
• Decision trees for tool selection

Automated profiling (CLI) → /skill axiom-xctrace-ref

• Headless xctrace profiling
• CI/CD integration patterns
• Command-line trace recording
• Programmatic trace analysis

Run automated profile → Use performance-profiler agent or /axiom:profile

• Records trace via xctrace
• Exports and analyzes data
• Reports findings with severity

Hang/Freeze Issues

App hangs or freezes → /skill axiom-hang-diagnostics

• UI unresponsive for >1 second
• Main thread blocked (busy or waiting)
• Decision tree: busy vs blocked diagnosis
• Time Profiler vs System Trace selection
• 8 common hang patterns with fixes
• Watchdog terminations

Energy Issues

Battery drain, high energy → /skill axiom-energy

• Power Profiler workflow
• Subsystem diagnosis (CPU/GPU/Network/Location/Display)
• Anti-pattern fixes
• Background execution optimization

Symptom-based diagnosis → /skill axiom-energy-diag

• "App at top of Battery Settings"
• "Device gets hot"
• "Background battery drain"
• Time-cost analysis for each path

API reference with code → /skill axiom-energy-ref

• Complete WWDC code examples
• Timer, network, location efficiency
• BGContinuedProcessingTask (iOS 26)
• MetricKit setup

Energy scan → Launch energy-auditor agent or /axiom:audit energy (8 anti-patterns: timer abuse, polling, continuous location, animation leaks, background mode misuse, network inefficiency, GPU waste, disk I/O)

Timer Safety

Timer crash patterns (DispatchSourceTimer) → /skill axiom-timer-patterns

• 4 crash scenarios causing EXC_BAD_INSTRUCTION
• RunLoop mode gotcha (Timer stops during scroll)
• SafeDispatchTimer wrapper
• Timer vs DispatchSourceTimer decision

Timer API reference → /skill axiom-timer-patterns-ref

• Timer, DispatchSourceTimer, Combine, AsyncTimerSequence APIs
• Lifecycle diagrams
• Platform availability

Swift Performance

Swift performance optimization → /skill axiom-swift-performance

• Value vs reference types, copy-on-write
• ARC overhead, generic specialization
• Collection performance

Swift performance scan → Launch swift-performance-analyzer agent or /axiom:audit swift-performance (unnecessary copies, ARC overhead, unspecialized generics, collection inefficiencies, actor isolation costs, memory layout)

Modern Swift idioms → /skill axiom-swift-modern

• Outdated API patterns (Date(), CGFloat, DateFormatter)
• Foundation modernization (URL.documentsDirectory, FormatStyle)
• Claude-specific hallucination corrections

MetricKit Integration

MetricKit API reference → /skill axiom-metrickit-ref

• MXMetricPayload parsing
• MXDiagnosticPayload (crashes, hangs)
• Field performance data collection
• Integration with crash reporting

Runtime Console Capture

Capture simulator console output → /skill axiom-xclog-ref or /axiom:console

• Capture print(), os_log(), Logger output from simulator
• Structured JSON with level, subsystem, category
• Bounded collection with --timeout and --max-lines
• Filter by subsystem or regex

Runtime State Inspection

LLDB interactive debugging → /skill axiom-lldb

• Set breakpoints, inspect variables at runtime
• Crash reproduction from crash logs
• Thread state analysis for hangs
• Swift value inspection (po vs v)

LLDB command reference → /skill axiom-lldb-ref

• Complete command syntax
• Breakpoint recipes
• Expression evaluation patterns

Decision Tree

1. Memory climbing + UI stutter/jank? → memory-debugging FIRST (memory pressure causes GC pauses that drop frames), then performance-profiling if memory is fixed but stutter remains
2. Memory leak (Swift)? → memory-debugging
3. Memory leak (Objective-C blocks)? → objc-block-retain-cycles
4. App hang/freeze — is UI completely unresponsive (can't tap, no feedback)?
   • YES → hang-diagnostics (busy vs blocked diagnosis)
   • NO, just slow → performance-profiling (Time Profiler)
   • First launch only? → Also check for synchronous I/O or lazy initialization in hang-diagnostics
5. Slowdown when multiple async operations complete at once? → Cross-route to axiom-ios-concurrency (callback contention, not profiling)
6. Battery drain (know the symptom)? → energy-diag
7. Battery drain (need API reference)? → energy-ref
8. Battery drain (general)? → energy
9. MetricKit setup/parsing? → metrickit-ref
10. Profile with GUI (Instruments)? → performance-profiling
11. Profile with CLI (xctrace)? → xctrace-ref
12. Run automated profile now? → performance-profiler agent
13. General slow/lag? → performance-profiling
14. Want proactive memory leak scan? → memory-auditor (Agent)
15. Want energy anti-pattern scan? → energy-auditor (Agent)
16. Want Swift performance audit (ARC, generics, collections)? → swift-performance-analyzer (Agent)
17. Need to inspect variable/thread state at runtime? → axiom-lldb
18. Need exact LLDB command syntax? → axiom-lldb-ref
19. Timer stops during scrolling? → timer-patterns (RunLoop mode)
20. EXC_BAD_INSTRUCTION crash with DispatchSourceTimer? → timer-patterns (4 crash patterns)
21. Choosing between Timer, DispatchSourceTimer, Combine timer, async timer? → timer-patterns
22. Need timer API syntax/lifecycle? → timer-patterns-ref
23. Code review for outdated Swift patterns? → swift-modern
24. Claude generating legacy APIs (DateFormatter, CGFloat, DispatchQueue)? → swift-modern
25. Need to see runtime console output before profiling? → xclog-ref or /axiom:console

Anti-Rationalization

Thought	Reality
"I know it's a memory leak, let me find it"	Memory leaks have 6 patterns. memory-debugging diagnoses the right one in 15 min vs 2 hours.
"I'll just run Time Profiler"	Wrong Instruments template wastes time. performance-profiling selects the right tool first.
"Battery drain is probably the network layer"	Energy issues span 8 subsystems. energy skill diagnoses the actual cause.
"App feels slow, I'll optimize later"	Performance issues compound. Profiling now saves exponentially more time later.
"It's just a UI freeze, probably a slow API call"	Freezes have busy vs blocked causes. hang-diagnostics has a decision tree for both.
"Memory is climbing AND scrolling stutters — two separate bugs"	Memory pressure causes GC pauses that drop frames. Fix the leak first, then re-check scroll performance.
"It only freezes on first launch, must be loading something"	First-launch hangs have 3 patterns: synchronous I/O, lazy initialization, main thread contention. hang-diagnostics diagnoses which.
"UI locks up when network requests finish — that's slow"	Multiple callbacks completing at once = main thread contention = concurrency issue. Cross-route to ios-concurrency.
"I'll just add print statements to debug this"	Print-debug cycles cost 3-5 min each (build + run + reproduce). An LLDB breakpoint costs 30 seconds. axiom-lldb has the commands.
"I can't see what the app is logging"	xclog captures print() + os_log from the simulator with structured JSON. /axiom:console or /skill axiom-xclog-ref.
"I'll just use Timer.scheduledTimer, it's simpler"	Timer stops during scrolling (.default mode), retains its target (leak). timer-patterns has the decision tree.
"DispatchSourceTimer crashed but it's intermittent, let's ship"	DispatchSourceTimer has 4 crash patterns that are ALL deterministic. timer-patterns diagnoses which one.
"Claude already knows modern Swift"	Claude defaults to pre-5.5 patterns (Date(), CGFloat, filter().count). swift-modern has the correction table.

Critical Patterns

Memory Debugging (memory-debugging):

• 6 leak patterns: timers, observers, closures, delegates, view callbacks, PhotoKit
• Instruments workflows
• Leak vs caching distinction

Performance Profiling (performance-profiling):

• Time Profiler for CPU bottlenecks
• Allocations for memory growth
• Core Data SQL logging for N+1 queries
• Self Time vs Total Time

Energy Optimization (energy):

• Power Profiler subsystem diagnosis
• 8 anti-patterns: timers, polling, location, animations, background, network, GPU, disk
• Audit checklists by subsystem
• Pressure scenarios for deadline resistance

Example Invocations

User: "My app's memory usage keeps growing" → Invoke: /skill axiom-memory-debugging

User: "I have a memory leak but deinit isn't being called" → Invoke: /skill axiom-memory-debugging

User: "My app feels slow, where do I start?" → Invoke: /skill axiom-performance-profiling

User: "My Objective-C block callback is leaking" → Invoke: /skill axiom-objc-block-retain-cycles

User: "My app drains battery quickly" → Invoke: /skill axiom-energy

User: "Users say the device gets hot when using my app" → Invoke: /skill axiom-energy-diag

User: "What's the best way to implement location tracking efficiently?" → Invoke: /skill axiom-energy-ref

User: "Profile my app's CPU usage" → Use: performance-profiler agent (or /axiom:profile)

User: "How do I run xctrace from the command line?" → Invoke: /skill axiom-xctrace-ref

User: "I need headless profiling for CI/CD" → Invoke: /skill axiom-xctrace-ref

User: "My app hangs sometimes" → Invoke: /skill axiom-hang-diagnostics

User: "The UI freezes and becomes unresponsive" → Invoke: /skill axiom-hang-diagnostics

User: "Main thread is blocked, how do I diagnose?" → Invoke: /skill axiom-hang-diagnostics

User: "How do I set up MetricKit?" → Invoke: /skill axiom-metrickit-ref

User: "How do I parse MXMetricPayload?" → Invoke: /skill axiom-metrickit-ref

User: "Scan my code for memory leaks" → Invoke: memory-auditor agent

User: "Check my app for battery drain issues" → Invoke: energy-auditor agent

User: "Audit my Swift code for performance anti-patterns" → Invoke: swift-performance-analyzer agent

User: "How do I inspect this variable in the debugger?" → Invoke: /skill axiom-lldb

User: "What's the LLDB command for conditional breakpoints?" → Invoke: /skill axiom-lldb-ref

User: "I need to reproduce this crash in the debugger" → Invoke: /skill axiom-lldb

User: "My list scrolls slowly and memory keeps growing" → Invoke: /skill axiom-memory-debugging first, then /skill axiom-performance-profiling if stutter remains

User: "App freezes for a few seconds on first launch then works fine" → Invoke: /skill axiom-hang-diagnostics

User: "UI locks up when multiple API calls return at the same time" → Cross-route: /skill axiom-ios-concurrency (callback contention)

User: "My timer stops when the user scrolls" → Invoke: /skill axiom-timer-patterns

User: "EXC_BAD_INSTRUCTION crash in my timer code" → Invoke: /skill axiom-timer-patterns

User: "Should I use Timer or DispatchSourceTimer?" → Invoke: /skill axiom-timer-patterns

User: "How do I create an AsyncTimerSequence?" → Invoke: /skill axiom-timer-patterns-ref

User: "Review my Swift code for outdated patterns" → Invoke: /skill axiom-swift-modern

User: "Is there a more modern way to do this?" → Invoke: /skill axiom-swift-modern

User: "What is the app logging? I need to see console output" → Invoke: /skill axiom-xclog-ref or /axiom:console

User: "Capture the simulator logs while I reproduce this bug" → Invoke: /skill axiom-xclog-ref or /axiom:console