Development

Use when debugging 'files disappeared', 'data missing after restart', 'backup too large', 'can't save file', 'file not found', 'storage full error', 'file inaccessible when locked' - systematic local file storage diagnostics

Symptom-based energy troubleshooting - decision trees for 'app at top of battery settings', 'phone gets hot', 'background drain', 'high cellular usage', with time-cost analysis for each diagnosis path

Use when UI is slow, scrolling lags, animations stutter, or when asking 'why is my SwiftUI view slow', 'how do I optimize List performance', 'my app drops frames', 'view body is called too often', 'List is laggy' - SwiftUI performance optimization with Instruments 26 and WWDC 2025 patterns

Reference — Complete Foundation Models framework guide covering LanguageModelSession, @Generable, @Guide, Tool protocol, streaming, dynamic schemas, built-in use cases, and all WWDC 2025 code examples

Use when implementing on-device AI with Apple's Foundation Models framework — prevents context overflow, blocking UI, wrong model use cases, and manual JSON parsing when @Generable should be used. iOS 26+, macOS 26+, iPadOS 26+, visionOS 26+

Use when implementing in-app purchases, StoreKit 2, subscriptions, or transaction handling - testing-first workflow with .storekit configuration, StoreManager architecture, transaction verification, subscription management, and restore purchases for consumables, non-consumables, and auto-renewable subscriptions

Use when writing unit tests, adopting Swift Testing framework, making tests run faster without simulator, architecting code for testability, testing async code reliably, or migrating from XCTest - covers @Test/@Suite macros,

Use when working with ANY data persistence, database, storage, CloudKit, migration, or serialization. Covers SwiftData, Core Data, GRDB, SQLite, CloudKit sync, file storage, Codable, migrations.

Reference — PHPickerViewController, PHPickerConfiguration, PhotosPicker, PhotosPickerItem, Transferable, PHPhotoLibrary, PHAsset, PHAssetCreationRequest, PHFetchResult, PHAuthorizationStatus, limited library APIs

Use when CAAnimation completion handler doesn't fire, spring physics look wrong on device, animation duration mismatches actual time, gesture + animation interaction causes jank, or timing differs between simulator and real hardware - systematic CAAnimation diagnosis with CATransaction patterns, frame rate awareness, and device-specific behavior

Use when adding/modifying database columns, encountering "FOREIGN KEY constraint failed", "no such column", "cannot add NOT NULL column" errors, or creating schema migrations for SQLite/GRDB/SQLiteData - prevents data loss with safe migration patterns and testing workflows for iOS/macOS apps

Use when converting shaders or looking up API equivalents - GLSL to MSL, HLSL to MSL, GL/DirectX to Metal mappings, MTKView setup code

Use when layouts need to adapt to different screen sizes, iPad multitasking, or iOS 26 free-form windows — decision trees for ViewThatFits vs AnyLayout vs onGeometryChange, size class limitations, and anti-patterns preventing device-based layout mistakes

Use when implementing haptic feedback, Core Haptics patterns, audio-haptic synchronization, or debugging haptic issues - covers UIFeedbackGenerator, CHHapticEngine, AHAP patterns, and Apple's Causality-Harmony-Utility design principles from WWDC 2021

Use when SwiftUI view debugging requires systematic investigation - view updates not working after basic troubleshooting, intermittent UI issues, complex state dependencies, or when Self._printChanges() shows unexpected update patterns - systematic diagnostic workflows with Instruments integration

Use when starting any iOS/Swift conversation - establishes how to find and use Axiom skills, requiring Skill tool invocation before ANY response including clarifying questions

Use when implementing widgets, Live Activities, Control Center controls, or app extensions - comprehensive API reference for WidgetKit, ActivityKit, App Groups, and extension lifecycle for iOS 14+

Complete energy optimization API reference - Power Profiler workflows, timer/network/location/background APIs, iOS 26 BGContinuedProcessingTask, MetricKit monitoring, with all WWDC code examples

Use when implementing SwiftUI animations, understanding VectorArithmetic, using @Animatable macro, zoom transitions, UIKit/AppKit animation bridging, choosing between spring and timing curve animations, or debugging animation behavior - comprehensive animation reference from iOS 13 through iOS 26

Use when profiling async/await performance, diagnosing actor contention, or investigating thread pool exhaustion. Covers Swift Concurrency Instruments template, task visualization, actor contention analysis, thread pool debugging.