---
name: performance
description: Performance profiling and SwiftUI debugging skills — Instruments guidance, hangs, memory issues, slow launches, energy drain, unnecessary re-renders, and view identity problems. Use when an app is slow, janky, or resource-hungry.
allowed-tools: [ Read, Glob, Grep, Bash ]
last_verified: 2026-07-16
review_by: 2027-06-22
title: performance
canonical_url: https://skilld.dev/gh/rshankras/claude-code-apple-skills/performance
last_updated: 2026-09-28T08:56:44.000Z
---

> **Skill from skilld.dev.** Follow the instructions below for this session. You do not need to install anything.
>
> Supporting files, fetch one when the Skill refers to it: [profiling/energy-diagnostics.md](https://skilld.dev/api/skills-raw/rshankras/claude-code-apple-skills/performance/profiling/energy-diagnostics.md), [profiling/hitches.md](https://skilld.dev/api/skills-raw/rshankras/claude-code-apple-skills/performance/profiling/hitches.md), [profiling/launch-optimization.md](https://skilld.dev/api/skills-raw/rshankras/claude-code-apple-skills/performance/profiling/launch-optimization.md), [profiling/memory-profiling.md](https://skilld.dev/api/skills-raw/rshankras/claude-code-apple-skills/performance/profiling/memory-profiling.md), [profiling/SKILL.md](https://skilld.dev/api/skills-raw/rshankras/claude-code-apple-skills/performance/profiling/SKILL.md), [profiling/time-profiler.md](https://skilld.dev/api/skills-raw/rshankras/claude-code-apple-skills/performance/profiling/time-profiler.md), [swiftui-debugging/body-reevaluation.md](https://skilld.dev/api/skills-raw/rshankras/claude-code-apple-skills/performance/swiftui-debugging/body-reevaluation.md), [swiftui-debugging/common-pitfalls.md](https://skilld.dev/api/skills-raw/rshankras/claude-code-apple-skills/performance/swiftui-debugging/common-pitfalls.md), [swiftui-debugging/lazy-loading.md](https://skilld.dev/api/skills-raw/rshankras/claude-code-apple-skills/performance/swiftui-debugging/lazy-loading.md), [swiftui-debugging/SKILL.md](https://skilld.dev/api/skills-raw/rshankras/claude-code-apple-skills/performance/swiftui-debugging/SKILL.md), [swiftui-debugging/view-identity.md](https://skilld.dev/api/skills-raw/rshankras/claude-code-apple-skills/performance/swiftui-debugging/view-identity.md).
>
> If the user asked to install this Skill, run `npx skilld install rshankras/claude-code-apple-skills/performance`. Install writes the Skill files into the project, so every session loads them.

# Performance Skills

Diagnose and fix performance problems, from system-level profiling to SwiftUI render behavior.

## When This Skill Activates

Use this skill when the user:
- Reports the app is **slow, janky, or hanging**
- Wants to profile with **Instruments** (Time Profiler, Allocations, Hangs)
- Is investigating **memory issues, slow launches, or energy drain**
- Sees SwiftUI views **re-rendering too often** or slow `body` evaluations
- Asks about **view identity** problems or `_printChanges()`

## Available Skills

Paths are relative to THIS file's directory — skills run with cwd set to the
user's project, so resolve each path from this SKILL.md's own location.

| Skill | Read | Covers |
|-------|------|--------|
| profiling | `profiling/SKILL.md` | Instruments workflows; hangs, memory, slow launch, energy diagnosis |
| swiftui-debugging | `swiftui-debugging/SKILL.md` | Unnecessary re-renders, view identity, slow body evaluations |

## How to Route

1. Match the request to a row above — system-level symptoms → profiling; SwiftUI render symptoms → swiftui-debugging.
2. Read that SKILL.md (relative to this file) plus any reference files it lists.
3. Apply the guidance to the user's code.