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 skills add kok-o/koko-contextos-agents --skill react-best-practicesgit clone --depth 1 https://github.com/kok-o/koko-contextos-agentsWrote 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/kok-o/koko-contextos-agents/react-best-practices)<a href="https://agentmods.dev/skills/kok-o/koko-contextos-agents/react-best-practices"><img src="https://agentmods.dev/badge/skills/kok-o/koko-contextos-agents/react-best-practices/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.
<a href="https://agentmods.dev/skills/kok-o/koko-contextos-agents/react-best-practices"><img src="https://agentmods.dev/badge/skills/kok-o/koko-contextos-agents/react-best-practices.svg" alt="Reviewed on agentmods" width="80" 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 5.1 | $0.00067 | $0.01770 |
| Opus 5.5 | $0.00027 | $0.00708 |
| Sonnet 5.5 | $0.00013 | $0.00354 |
| Haiku 4.5 | $0.00007 | $0.00177 |
Grade A, and why
vercel-react-best-practices 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 1mo 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.
This is a copy
97% identical to react-performance — 193 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.
How it starts
The opening of the file, as written. The whole thing — 156 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Vercel React Best Practices
Overview
Comprehensive performance optimization guide for React and Next.js applications, maintained by Vercel. Contains 70 rules across 8 categories, prioritized by impact to guide automated refactoring, code generation, and production review.
When to Use
- When authoring new React functional components or Next.js App Router pages.
- When implementing data fetching (client or server-side Server Actions, RSC).
- When reviewing pull requests for rendering bottlenecks or memory leaks.
- When optimizing bundle size, eliminating network waterfalls, or improving Core Web Vitals (LCP, INP, CLS).
Rules & Patterns
Rule Categories by Priority
| Priority | Category | Impact | Prefix |
|---|---|---|---|
| 1 | Eliminating Waterfalls | CRITICAL | async- |
| 2 | Bundle Size Optimization | CRITICAL | bundle- |
| 3 | Server-Side Performance | HIGH | server- |
| 4 | Client-Side Data Fetching | MEDIUM-HIGH | client- |
| 5 | Re-render Optimization | MEDIUM | rerender- |
| 6 | Rendering Performance | MEDIUM | rendering- |
| 7 | JavaScript Performance | LOW-MEDIUM | js- |
| 8 | Advanced Patterns | LOW | advanced- |
1. Eliminating Waterfalls (CRITICAL)
async-cheap-condition-before-await- Check cheap sync conditions before awaiting flags or remote values.async-defer-await- Move await into branches where actually used.async-parallel- UsePromise.all()for independent asynchronous operations.async-dependencies- Use better-all for partial dependencies.async-api-routes- Start promises early, await late in API routes.async-suspense-boundaries- Use Suspense to stream content progressively.
2. Bundle Size Optimization (CRITICAL)
bundle-barrel-imports- Import directly from specific modules, avoid broad barrel files (index.ts).bundle-analyzable-paths- Prefer statically analyzable import paths to avoid bloated traces.bundle-dynamic-imports- Usenext/dynamicorReact.lazy()for heavy interactive components.bundle-defer-third-party- Load analytics and logging scripts after hydration.bundle-conditional- Load modules only when feature flags or user actions require them.bundle-preload- Preload assets on hover or focus for perceived instant navigation.
What ships with it
2 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.
- 1mo ago Changed · +6 lines 5525e303a7c6
- 1mo ago First seen · 150 lines · 67 tokens per session scan A 71ed7794962f
vercel-react-best-practices is a skill published in the GitHub repository kok-o/koko-contextos-agents (2 stars, last pushed 1mo ago), licensed MIT. It adds 67 tokens to every session and 1,770 once invoked, about $0.0003 per session on Opus 5.5. A static security scan graded it A with 0 findings. It is 97% identical to react-performance, differing in 193 lines, and is treated as a copy.
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