Use this skill when reviewing or fixing SwiftUI performance issues, including unnecessary invalidation, unstable identity, broad state dependencies, expensive body work, heavy rows, scrolling hitches, layout/drawing cost, or async lifecycle work. Do not use it for general SwiftUI syntax, styling, UIKit-only performance, or generic profiling unless SwiftUI update behavior is central.
Use this skill when diagnosing iOS app launch performance, startup regressions, first-frame readiness, or early responsiveness. Covers pre-main/dyld work, AppDelegate/SceneDelegate, SwiftUI App startup, launch orchestration, SDK initialization, and launch measurement. Do not use for general performance unless the code runs on the launch path.
Use this skill for product-level iOS responsiveness and loading/feedback flows, including perceived latency, time to first feedback, progressive rendering, loading states, skeletons, placeholders, optimistic updates, rollback behavior, high-stakes actions, UI continuity, and responsiveness validation. Do not use it for low-level CPU, memory, rendering, Swift Concurrency, or launch-performance diagnostics unless the task is about user-perceived speed.
Use this skill when choosing, running, or interpreting iOS performance profiling workflows, including Instruments traces, signposts, XCTest metrics, MetricKit, Xcode Organizer, hangs, hitches, CPU, allocations, memory graphs, disk I/O, networking, power, or production performance signals. Do not use it as the deep domain skill for launch, SwiftUI, concurrency, perceived performance, or runtime issues unless the task is specifically about measurement, tool selection, trace interpretation, or verification.
Use this skill when reviewing Swift Concurrency performance and responsiveness, including task explosions, actor hopping, MainActor bottlenecks, cancellation, AsyncSequence cleanup, continuations, reentrancy, executor behavior, blocking async work, or async work that affects UI latency. Do not use it for general async/await syntax questions unless performance, responsiveness, cancellation, or lifetime is part of the task.
Use this skill when reviewing Swift code for runtime-level performance costs, including heap allocation, ARC traffic, stack vs heap storage, closure capture contexts, method dispatch, protocol witness dispatch, existentials vs generics, opaque types, copy-on-write, SIL optimizer output, unsafe memory boundaries, or module-boundary optimizer visibility. Do not use it for Swift Concurrency scheduling, SwiftUI rendering, app launch, or profiling workflows unless the question is specifically about Swift runtime costs.