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.
git 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/rules/kok-o/koko-contextos-agents/react-best-practices)<a href="https://agentmods.dev/rules/kok-o/koko-contextos-agents/react-best-practices"><img src="https://agentmods.dev/badge/rules/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/rules/kok-o/koko-contextos-agents/react-best-practices"><img src="https://agentmods.dev/badge/rules/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 | $0.00013 | $0.01711 |
| Opus 5 | $0.00006 | $0.00856 |
| Sonnet 5 | $0.00003 | $0.00342 |
| Haiku 4.5 | $0.00001 | $0.00171 |
Grade A, and why
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 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.
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.
Skill: react-best-practices
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 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 · 156 lines · 13 tokens per session scan A 1c48d207939e
react-best-practices is a cursor rule published in the GitHub repository kok-o/koko-contextos-agents (2 stars, last pushed 5d ago), licensed MIT. It adds 13 tokens to every session and 1,711 once invoked, about $0.0001 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 2026-09-05.
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