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swiftui-performance

Profile, diagnose, and remediate SwiftUI runtime performance using code review, Instruments, and repeatable measurements. Use when a SwiftUI screen renders slowly, scrolling or animations hitch, view bodies update excessively, list identity churns, layout work spikes, or broad Observation dependencies raise CPU cost. Covers evidence-based triage, SwiftUI Instruments lanes, lazy-container guardrails, state lifetime, and before/after verification.

Quality

91%

Does it follow best practices?

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SecuritybySnyk

Passed

No findings from the security scan

The canonical home for this skill is dpearson2699/swift-ios-skills

SKILL.md
Quality
Evals
Security

Quality

Content

85%Weight 40%Scale 1-5

Reviews the quality of instructions and guidance provided to agents. Good implementation is clear, handles edge cases, and produces reliable results.

A well-structured performance-audit skill with a clear evidence-driven workflow, executable snippets, and clean reference splitting. Minor trims of concept-restating sentences and one or two concrete examples for underspecified fixes (image downsampling, off-main-actor work) would close the remaining gaps.

Suggestions

Trim sentences that restate known SwiftUI semantics (e.g., 'Identity controls view lifetime and state', 'Observation tracks properties read during view evaluation') — keep only the prescriptive guidance that follows them.

Add a short concrete example for the two remediation items currently given only as direction: image downsampling (e.g., ImageIO thumbnail API) and an off-main-actor decode/parse helper.

Consider moving the eight-item Common Mistakes list or the lazy-container guardrails into a reference file to further slim SKILL.md, since the checklist and smells table already cover the same ground at audit time.

DimensionReasoningScore

Conciseness

The body is dense and skill-specific: a smells table, guardrail lists, version-specific flags ('-LogForEachSlowPath YES', '.onGeometryChange (iOS 16+)'), and non-obvious techniques like Self._printChanges() and observation-splitting. Not 5 because a few sentences restate concepts Claude already knows (e.g., 'Identity controls view lifetime and state', 'Observation tracks properties read during view evaluation') and could be trimmed.

4 / 5

Actionability

Executable code snippets are copy-paste ready ('#if DEBUG let _ = Self._printChanges() #endif', the split-reads ProfileView, ForEach with .id(item.stableID)) and tooling is concrete (named Instruments lanes, Cmd+I, -LogForEachSlowPath YES). Not 5 because two remediation items ('Downsample images before rendering', moving work off MainActor) give direction without a concrete example, leaving minor gaps.

4 / 5

Workflow Clarity

A decision tree plus a clearly numbered 5-phase workflow (review, profile, diagnose, remediate, verify) with built-in checkpoints: findings are labeled hypotheses until trace-confirmed, and the Verify step re-runs the same capture against baseline. A review checklist closes the loop. This matches the top anchor including explicit validation and a feedback loop.

5 / 5

Progressive Disclosure

The body is a navigable overview with a TOC, a well-signaled inline pointer to the profiling reference, and a References section listing five real one-level-deep files (verified to exist; reference files link only to external URLs, not nested .md chains). Deep WWDC/Instruments material is appropriately split out while the working checklists stay inline. Matches the top anchor.

5 / 5

Total

18

/

20

Passed

Description

92%Weight 40%Scale 1-5

Based on the skill's description, can an agent find and select it at the right time? Clear, specific descriptions lead to better discovery.

A strong description with clear third-person capabilities, an explicit 'Use when' clause with concrete symptom triggers, and well-scoped distinctiveness. The only gap is missing a few natural synonyms (laggy, janky, frame drops) that users commonly use for performance complaints.

DimensionReasoningScore

Specificity

Concrete actions ('Profile, diagnose, and remediate ... using code review, Instruments, and repeatable measurements') plus an enumerated coverage list ('evidence-based triage, SwiftUI Instruments lanes, lazy-container guardrails, state lifetime, and before/after verification') give comprehensive, specific capability coverage. Not 4 because coverage has no meaningful gaps; the actions go beyond naming the domain.

5 / 5

Completeness

Explicitly answers both: what ('Profile, diagnose, and remediate SwiftUI runtime performance...') and when ('Use when a SwiftUI screen renders slowly, scrolling or animations hitch...') with concrete trigger phrases. Third-person voice is correct. Nothing below 5 applies since both parts are explicit and specific.

5 / 5

Trigger Term Quality

Natural symptom phrases users would say ('screen renders slowly', 'scrolling or animations hitch', 'view bodies update excessively', 'layout work spikes', 'raise CPU cost') are present and specific. Not 5 because common synonyms like 'laggy', 'janky', 'stuttering', or 'frame drops' are missing; not 3 because keyword coverage clearly exceeds 'some relevant keywords'.

4 / 5

Distinctiveness Conflict Risk

A clear niche (SwiftUI runtime performance) with distinct symptom-based triggers (hitches, body-update churn, Observation fan-out) that would not fire for sibling skills like swiftui-animation or metrickit. Not 4 because the symptom triggers and tooling scope make overlap risk minimal.

5 / 5

Total

19

/

20

Passed

Validation

100%

Checks the skill against the spec for correct structure and formatting. All validation checks must pass before discovery and implementation can be scored.

Validation — 16 / 16 Passed

Validation for skill structure

No warnings or errors.

Repository

dpearson2699/swift-ios-skills

Path

skills/swiftui-performance/SKILL.md

Reviewed

Table of Contents

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