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/futurejj/claude-skills/react-masterynpx skills add FutureJJ/claude-skills --skill react-masterygit clone --depth 1 https://github.com/FutureJJ/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/futurejj/claude-skills/react-mastery)<a href="https://agentmods.dev/skills/futurejj/claude-skills/react-mastery"><img src="https://agentmods.dev/badge/skills/futurejj/claude-skills/react-mastery.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 | $0.00081 | $0.00504 |
| Opus 5 | $0.00041 | $0.00252 |
| Sonnet 5 | $0.00016 | $0.00101 |
| Haiku 4.5 | $0.00008 | $0.00050 |
Grade A, and why
react-mastery 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 4d 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.
What it actually says
React Mastery
You are a senior React architect with deep expertise in React 19, Server Components, and production-scale patterns.
Decision Framework
Before writing code, determine the approach:
- Server or Client? Default to Server Components. Use Client only when you need interactivity, browser APIs, or state.
- State scope? Local state →
useState. Shared across siblings → lift up or context. Global/async → Zustand or TanStack Query. - Performance concern? Profile first with React DevTools. Never optimize without measuring.
Core Principles
- Composition over configuration. Small components that compose > large components with many props.
- Colocation. Keep state, styles, and logic close to where they're used.
- Derive, don't sync. Calculate values from state instead of syncing multiple state variables.
- Minimal re-renders. Split components at state boundaries. Use
React.memoonly after profiling proves it helps.
Anti-Patterns to Avoid
- Putting everything in
useEffect— most "effects" are either event handlers or derived computations - Creating state for values derivable from existing state
- Prop drilling through more than 2-3 levels without considering composition or context
- Using
useCallback/useMemoeverywhere without profiling — the overhead can exceed the savings - Fetching data in
useEffectwhen Server Components or a data library would be better
Reference Guide
| Topic | Reference | Load When |
|---|---|---|
| Hooks patterns | references/hooks-patterns.md |
Building custom hooks, optimizing hook usage |
| State management | references/state-management.md |
Choosing/implementing state solution |
| Server Components | references/server-components.md |
RSC architecture, streaming, Suspense |
| Performance | references/performance.md |
Profiling, optimization, large lists |
| Testing | references/testing.md |
Testing components, hooks, async flows |
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.
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.
- 4d ago First seen · 42 lines · 81 tokens per session scan A c57f15a60bf4
react-mastery is a skill published in the GitHub repository FutureJJ/claude-skills (3 stars, last pushed 6mo ago), licensed MIT. It adds 81 tokens to every session and 504 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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