nucleus-apple-mcp: Skill for Claude Code

.agents/skills/swiftui-performance/SKILL.md

swiftui-performance is a skill for Claude Code, Codex from zish-rob-crur/nucleus-apple-mcp. It costs 59 tokens per session (3,924 once invoked), scanned A, original, MIT.

A guide for finding and fixing runtime performance problems in SwiftUI views.

In plain words
What is it for?
Reviewing view code, state and identity behavior, lazy loading, layout work, and Instruments profiling results, then applying targeted fixes.
Why use it?
It helps explain slow rendering, jerky scrolling, excessive updates, high CPU use, and memory problems in SwiftUI apps.

Skill for Claude CodeCodex

Written for no agent in particular: nothing here depends on one. Also seen: positional $N argument; installed under .agents/ (shared by several agents).

This is zish-rob-crur/nucleus-apple-mcp's own configuration. It tells Claude Code and Codex how to work on nucleus-apple-mcp itself, so it is not a mod to install elsewhere. Copy it as a starting point and replace the rules that are about this project. Everything nucleus-apple-mcp configures →

Reuse

Borrowing it

Nothing to install: this file belongs to zish-rob-crur/nucleus-apple-mcp. Take a copy, put it at the same path in your own repository, and replace the rules that are about this project with yours.

Copy the file
curl -O https://raw.githubusercontent.com/zish-rob-crur/nucleus-apple-mcp/main/.agents/skills/swiftui-performance/SKILL.md
Clone the repo
git clone --depth 1 https://github.com/zish-rob-crur/nucleus-apple-mcp

Made for: Claude Code, Codex.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

agentmods badge for swiftui-performance

README.md
[![agentmods](https://agentmods.dev/badge/skills/zish-rob-crur/nucleus-apple-mcp/swiftui-performance/github.svg)](https://agentmods.dev/skills/zish-rob-crur/nucleus-apple-mcp/swiftui-performance)
Your own site
<a href="https://agentmods.dev/skills/zish-rob-crur/nucleus-apple-mcp/swiftui-performance"><img src="https://agentmods.dev/badge/skills/zish-rob-crur/nucleus-apple-mcp/swiftui-performance/github.svg" alt="Measured on agentmods" height="20"></a>

Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.

agentmods 80×15 button for swiftui-performance

Your own site · 80×15
<a href="https://agentmods.dev/skills/zish-rob-crur/nucleus-apple-mcp/swiftui-performance"><img src="https://agentmods.dev/badge/skills/zish-rob-crur/nucleus-apple-mcp/swiftui-performance.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 59 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 3,924 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe. Third-party audits
  • NVIDIA SkillSpector pass 7 Sept 2026
How audits are shown
Origin original No closer match found 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 5.1 $0.00059 $0.03924
Opus 5 $0.00030 $0.01962
Sonnet 5 $0.00012 $0.00785
Haiku 4.5 $0.00006 $0.00392

Measured 12d ago against content hash 17b4548865e8, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-11, from the pricing page.

Security

Grade A, and why

swiftui-performance 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 12d ago.

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.

.agents/skills/swiftui-performance/SKILL.md · 476 lines

How it starts

The opening of the file, as written. The whole thing — 476 lines — stays where its author put it; the contents beside it link to each section on GitHub.

SwiftUI Performance

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

Contents

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.
  • Profile a Release build on a real device when possible.
  • Reproduce the exact interaction (scroll, navigation, animation).
  • Capture SwiftUI timeline and Time Profiler.
  • Export or screenshot the relevant lanes and the call tree.

Read the full file on GitHub · 476 lines

Files

What ships with it

5 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. 12d ago First seen · 476 lines · 59 tokens per session scan A 17b4548865e8

Subscribe to this mod's changes

swiftui-performance is a skill published in the GitHub repository zish-rob-crur/nucleus-apple-mcp (20 stars, last pushed 7d ago), licensed MIT. It adds 59 tokens to every session and 3,924 once invoked, about $0.0003 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.

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