# Guide Swiftui Performance Audit > Audit and improve SwiftUI runtime performance from code review and architecture. Use for requests to diagnose slow rendering, janky scrolling, high CPU/memory usage, excessive view updates, or layout thrash in SwiftUI apps, and to provide guidance for user-run Instruments profiling when code review alone is insufficient. - **Type:** Skill - **Install:** `agentstack add skill-vabole-apple-skills-guide-swiftui-performance-audit` - **Verified:** Yes — security-reviewed for prompt injection and unsafe behavior - **Seller:** [vabole](https://agentstack.voostack.com/s/vabole) - **Installs:** 0 - **Category:** [Agent Skills](https://agentstack.voostack.com/c/agent-skills) - **Latest version:** 0.1.0 - **License:** MIT - **Upstream author:** [vabole](https://github.com/vabole) - **Source:** https://github.com/vabole/apple-skills/tree/main/skills/guide-swiftui-performance-audit ## Install ```sh agentstack add skill-vabole-apple-skills-guide-swiftui-performance-audit ``` Requires the [AgentStack CLI](https://agentstack.voostack.com/docs/cli). Works with Claude Code, Cursor, and any MCP-compatible agent. ## About > **Guide Skill** — This is an expert workflow/pattern guide, not API reference documentation. > Originally from [Dimillian/Skills](https://github.com/Dimillian/Skills) by Thomas Ricouard. MIT License. # SwiftUI Performance Audit ## Quick start Use this skill to diagnose SwiftUI performance issues from code first, then request profiling evidence when code review alone cannot explain the symptoms. ## Workflow 1. Classify the symptom: slow rendering, janky scrolling, high CPU, memory growth, hangs, or excessive view updates. 2. If code is available, start with a code-first review using `references/code-smells.md`. 3. If code is not available, ask for the smallest useful slice: target view, data flow, reproduction steps, and deployment target. 4. If code review is inconclusive or runtime evidence is required, guide the user through profiling with `references/profiling-intake.md`. 5. Summarize likely causes, evidence, remediation, and validation steps using `references/report-template.md`. ## 1. Intake Collect: - Target view or feature code. - Symptoms and exact reproduction steps. - Data flow: `@State`, `@Binding`, environment dependencies, and observable models. - Whether the issue shows up on device or simulator, and whether it was observed in Debug or Release. Ask the user to classify the issue if possible: - CPU spike or battery drain - Janky scrolling or dropped frames - High memory or image pressure - Hangs or unresponsive interactions - Excessive or unexpectedly broad view updates For the full profiling intake checklist, read `references/profiling-intake.md`. ## 2. Code-First Review Focus on: - Invalidation storms from broad observation or environment reads. - Unstable identity in lists and `ForEach`. - Heavy derived work in `body` or view builders. - Layout thrash from complex hierarchies, `GeometryReader`, or preference chains. - Large image decode or resize work on the main thread. - Animation or transition work applied too broadly. Use `references/code-smells.md` for the detailed smell catalog and fix guidance. Provide: - Likely root causes with code references. - Suggested fixes and refactors. - If needed, a minimal repro or instrumentation suggestion. ## 3. Guide the User to Profile If code review does not explain the issue, ask for runtime evidence: - A trace export or screenshots of the SwiftUI timeline and Time Profiler call tree. - Device/OS/build configuration. - The exact interaction being profiled. - Before/after metrics if the user is comparing a change. Use `references/profiling-intake.md` for the exact checklist and collection steps. ## 4. Analyze and Diagnose - Map the evidence to the most likely category: invalidation, identity churn, layout thrash, main-thread work, image cost, or animation cost. - Prioritize problems by impact, not by how easy they are to explain. - Distinguish code-level suspicion from trace-backed evidence. - Call out when profiling is still insufficient and what additional evidence would reduce uncertainty. ## 5. Remediate Apply targeted fixes: - Narrow state scope and reduce broad observation fan-out. - Stabilize identities for `ForEach` and lists. - Move heavy work out of `body` into derived state updated from inputs, model-layer precomputation, memoized helpers, or background preprocessing. Use `@State` only for view-owned state, not as an ad hoc cache for arbitrary computation. - Use `equatable()` only when equality is cheaper than recomputing the subtree and the inputs are truly value-semantic. - Downsample images before rendering. - Reduce layout complexity or use fixed sizing where possible. Use `references/code-smells.md` for examples, Observation-specific fan-out guidance, and remediation patterns. ## 6. Verify Ask the user to re-run the same capture and compare with baseline metrics. Summarize the delta (CPU, frame drops, memory peak) if provided. ## Outputs Provide: - A short metrics table (before/after if available). - Top issues (ordered by impact). - Proposed fixes with estimated effort. Use `references/report-template.md` when formatting the final audit. ## References - Profiling intake and collection checklist: `references/profiling-intake.md` - Common code smells and remediation patterns: `references/code-smells.md` - Audit output template: `references/report-template.md` - Add Apple documentation and WWDC resources under `references/` as they are supplied by the user. - Optimizing SwiftUI performance with Instruments: `references/optimizing-swiftui-performance-instruments.md` - Understanding and improving SwiftUI performance: `references/understanding-improving-swiftui-performance.md` - Understanding hangs in your app: `references/understanding-hangs-in-your-app.md` - Demystify SwiftUI performance (WWDC23): `references/demystify-swiftui-performance-wwdc23.md` ## Source & license This open-source skill is cataloged on AgentStack and links to its original source — we do not rehost the code. - **Author:** [vabole](https://github.com/vabole) - **Source:** [vabole/apple-skills](https://github.com/vabole/apple-skills) - **License:** MIT Install and usage instructions live in the source repository linked above. ## Pricing - **Free** — Free ## Security capabilities Automated source analysis of v0.1.0 — what this tool can access: - **Network access:** no - **Filesystem access:** no - **Shell / process execution:** no - **Environment & secrets:** no - **Dynamic code execution:** no *"Yes" means the capability is present in the source — more access means more to trust, not that it is unsafe.* ## Versions - **0.1.0** — security scan: passed — Imported from the upstream source. ## Links - Listing page: https://agentstack.voostack.com/l/skill-vabole-apple-skills-guide-swiftui-performance-audit - Seller: https://agentstack.voostack.com/s/vabole - Browse the marketplace: https://agentstack.voostack.com/browse --- Listed on AgentStack — the marketplace for AI agent skills and MCP servers. Every listing is security-reviewed. Creators keep 70%.