Diagnose SwiftUI rendering, scrolling, update, CPU, memory, image, layout, and animation performance from code and evidence. Use when a SwiftUI feature is slow, janky, broadly invalidating, memory-heavy, or needs a code-first audit before Instruments capture.
Installation
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Diagnose SwiftUI rendering, scrolling, update, CPU, memory, image, layout, and animation performance from code and evidence. Use when a SwiftUI feature is slow, janky, broadly invalidating, memory-heavy, or needs a code-first audit before Instruments capture.
SwiftUI Performance Audit
Purpose
Make performance work evidence-led: inspect the smallest relevant SwiftUI data-flow and view slice first, name code-level suspicion separately from runtime proof, then hand trace capture to the existing Xcode or SwiftPM testing workflow.
When To Use
Use for slow rendering, dropped frames, broad view updates, unstable list identity, expensive body work, layout churn, image pressure, broad animation, high CPU, or memory growth in SwiftUI.
Do not use this skill as a generic style review, a replacement for Instruments, or a reason to introduce caches, view models, stores, or coordinators.
Single-Path Workflow
Apply the Apple docs gate through explore-apple-swift-docs. Confirm current Observation and SwiftUI behavior before proposing a performance change.
Collect the target view, reproduction steps, data flow, device/simulator, build configuration, and the observed symptom.
Classify the symptom as invalidation, identity churn, body computation, layout, image, animation, CPU, or retained-memory pressure.
Read references/code-smells-and-remediation.md and identify only code-backed suspicions. Mark each finding as suspected until a capture proves it.
Prefer narrow ownership, stable identity, precomputation outside body, downsampled images, localized state, and reduced layout complexity. Do not use equatable() or @State as an unmeasured cache.
When code inspection is insufficient, hand trace capture to xcode-testing-workflow for scheme/destination work or swift-package-testing-workflow for package-first workloads.
Compare the same reproduction before and after the change. Report CPU, frame behavior, allocations, and view-update evidence only when captured.
Inputs
target view/feature, smallest reproduction, and symptom
state/observation/data-flow slice and relevant identities
platform, device or simulator, build configuration, and any existing trace
Outputs
findings labeled as code-level suspicion or trace-backed evidence
smallest remediation proposal with ownership and behavior preserved
profiling handoff or before/after validation result
Guards and Stop Conditions
Do not claim a view is the performance root cause without code evidence or a trace.
Do not add a ViewModel, repository, service wrapper, or arbitrary @State cache merely to quiet a symptom.
Do not compare Debug and Release captures as if they are the same measurement.
Stop when the reproduction is not defined well enough to distinguish a product behavior from a performance regression.
Fallbacks and Handoffs
Recommend xcode-testing-workflow for Instruments, xctrace, schemes, destinations, and trace interpretation.
Recommend swift-package-testing-workflow for package-first signposts and profiling workloads.
Recommend swiftui-app-architecture-workflow or swiftui-component-audit-workflow only when the evidence shows a real component-ownership issue.
Customization
Use references/customization-flow.md. The workflow has no knobs that can weaken the distinction between a code suspicion and trace-backed performance evidence.
References
references/code-smells-and-remediation.md
references/customization-flow.md
Recommend references/snippets/apple-xcode-project-core.md when the app needs reusable Xcode-project policy alongside profiling work.
