swiftui-performance-audit

A code-review skill for SwiftUI, Apple's framework for building app screens with Swift. It examines how views, state, data, images, animations, and layouts affect runtime speed and responsiveness.

In plain words
What is it for?
Use it to review SwiftUI code, find excessive view updates, unstable list identity, expensive work in screen rendering, layout problems, oversized images, or too many animations, then suggest targeted fixes.
Why use it?
It helps explain slow rendering, jerky scrolling, high processor or memory use, and unnecessary screen updates. When code review cannot prove the cause, it guides you through profiling with Instruments, Apple's performance-analysis tool.

Skill for Claude CodeCodex

Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

agentmods
npx agentmods add skills/hack-dance/hack/swiftui-performance-audit
Any agent
npx skills add hack-dance/hack --skill swiftui-performance-audit
Clone the repo
git clone --depth 1 https://github.com/hack-dance/hack

Made for: Claude Code, Codex.

Per session 66 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 1,353 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
Origin 100% copy Near-identical to another mod in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5 $0.00066 $0.01353
Opus 5 $0.00033 $0.00677
Sonnet 5 $0.00013 $0.00271
Haiku 4.5 $0.00007 $0.00135

Measured yesterday against content hash ff2db94adc31, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

swiftui-performance-audit scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured yesterday.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

Origin

This is a copy

100% identical to swiftui-performance-audit — 0 lines differ, which has more behind it and is treated as the original. This page carries a canonical link to it rather than competing with it.

.agents/skills/swiftui-performance-audit/SKILL.md · 204 lines

How it starts

The opening of the file, as written. The whole thing — 204 lines — stays where its author put it; the contents beside it link to each section on GitHub.

SwiftUI Performance Audit

Overview

Audit SwiftUI view performance end-to-end, from instrumentation and baselining to root-cause analysis and concrete remediation steps.

Workflow Decision Tree

  • If the user provides code, start with "Code-First Review."
  • If the user only describes symptoms, ask for minimal code/context, then do "Code-First Review."
  • If code review is inconclusive, go to "Guide the User to Profile" and ask for a trace or screenshots.

1. Code-First Review

Collect:

  • Target view/feature code.
  • Data flow: state, environment, observable models.
  • Symptoms and reproduction steps.

Focus on:

  • View invalidation storms from broad state changes.
  • Unstable identity in lists (id churn, UUID() per render).
  • Top-level conditional view swapping (if/else returning different root branches).
  • Heavy work in body (formatting, sorting, image decoding).
  • Layout thrash (deep stacks, GeometryReader, preference chains).
  • Large images without downsampling or resizing.
  • Over-animated hierarchies (implicit animations on large trees).

Provide:

  • Likely root causes with code references.
  • Suggested fixes and refactors.
  • If needed, a minimal repro or instrumentation suggestion.

2. Guide the User to Profile

Explain how to collect data with Instruments:

  • Use the SwiftUI template in Instruments (Release build).
  • Reproduce the exact interaction (scroll, navigation, animation).
  • Capture SwiftUI timeline and Time Profiler.
  • Export or screenshot the relevant lanes and the call tree.

Ask for:

  • Trace export or screenshots of SwiftUI lanes + Time Profiler call tree.
  • Device/OS/build configuration.

3. Analyze and Diagnose

Prioritize likely SwiftUI culprits:

  • View invalidation storms from broad state changes.
  • Unstable identity in lists (id churn, UUID() per render).
  • Top-level conditional view swapping (if/else returning different root branches).
  • Heavy work in body (formatting, sorting, image decoding).
  • Layout thrash (deep stacks, GeometryReader, preference chains).
  • Large images without downsampling or resizing.
  • Over-animated hierarchies (implicit animations on large trees).

Read the full file on GitHub · 204 lines

Files

What ships with it

4 files beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. yesterday First seen · 204 lines · 66 tokens per session scan A ff2db94adc31

Subscribe to this mod's changes

swiftui-performance-audit is a skill published in the GitHub repository hack-dance/hack (8 stars, last pushed 20d ago), licensed MIT. It adds 66 tokens to every session and 1,353 once invoked, about $0.0003 per session on Opus 5. A static security scan graded it A with 0 findings. It is 100% identical to swiftui-performance-audit, differing in 0 lines, and is treated as a copy.

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