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.
npx agentmods add skills/leahycc/claude-skills/react-performancenpx skills add LeahyCC/claude-skills --skill react-performancegit clone --depth 1 https://github.com/LeahyCC/claude-skillsWrote 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.
[](https://agentmods.dev/skills/leahycc/claude-skills/react-performance)<a href="https://agentmods.dev/skills/leahycc/claude-skills/react-performance"><img src="https://agentmods.dev/badge/skills/leahycc/claude-skills/react-performance.svg" alt="Measured on agentmods" height="20"></a>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.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5 | $0.00072 | $0.01814 |
| Opus 5 | $0.00036 | $0.00907 |
| Sonnet 5 | $0.00014 | $0.00363 |
| Haiku 4.5 | $0.00007 | $0.00181 |
Grade A, and why
react-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 5d 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.
How it starts
The opening of the file, as written. The whole thing — 144 lines — stays where its author put it; the contents beside it link to each section on GitHub.
React Performance
Comprehensive React performance guidance covering measurement, rendering optimization, bundle size, Core Web Vitals, and Server Component patterns. Verified against React docs and Web Vitals specifications.
First principle: Measure before you optimize. This skill teaches you to find problems before fixing them.
Architecture Overview
[Diagnose]
├── React DevTools Profiler (component render times)
├── Chrome Performance Panel (main thread activity)
├── web-vitals library (LCP, INP, CLS in production)
└── Bundle analyzer (what's in the bundle)
↓
[Identify Root Cause]
├── Unnecessary re-renders? → Memoization / state colocation
├── Slow initial load? → Code splitting / Server Components
├── Janky interactions? → useTransition / useDeferredValue
├── Layout shifts? → Image/font optimization
└── Large bundle? → Dynamic imports / tree shaking
↓
[Fix — Least Invasive First]
├── 1. Restructure components (children pattern, local state)
├── 2. Enable React Compiler (auto-memoization)
├── 3. Use concurrent features (transitions, deferred values)
├── 4. Move work to Server Components
├── 5. Code split heavy dependencies
└── 6. Manual memo/useMemo/useCallback (last resort)
Quick Reference
| Need to... | See |
|---|---|
| Measure performance before optimizing | Profiling and Measurement |
| Fix unnecessary re-renders | Rendering Optimization |
| Reduce JavaScript bundle size | Bundle Optimization |
| Fix LCP, INP, or CLS scores | Core Web Vitals |
| Decide Server vs Client Components | Server Components |
| Handle large lists and data sets | Data and Lists |
| Optimize images, fonts, and media | Assets |
| Decide when React Compiler handles it | React Compiler |
What ships with it
9 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.
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.
- 5d ago First seen · 144 lines · 72 tokens per session scan A ec51148a22c7
react-performance is a skill published in the GitHub repository LeahyCC/claude-skills (3 stars, last pushed 1mo ago), licensed MIT. It adds 72 tokens to every session and 1,814 once invoked, about $0.0004 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 2026-08-31.
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