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 rules/kok-o/koko-contextos-agents/nextjsgit 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/nextjs)<a href="https://agentmods.dev/rules/kok-o/koko-contextos-agents/nextjs"><img src="https://agentmods.dev/badge/rules/kok-o/koko-contextos-agents/nextjs.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 | $0.00000 | $0.01130 |
| Opus 5 | $0.00000 | $0.00565 |
| Sonnet 5 | $0.00000 | $0.00226 |
| Haiku 4.5 | $0.00000 | $0.00113 |
Grade A, and why
nextjs 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 3d 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 — 124 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Skill: Next.js
Next.js App Router Best Practices
Overview
Enforces high-performance architectural patterns for Next.js App Router based on Vercel Engineering guidelines: React Server Components (RSC), zero-waterfall async pipelines, request deduplication via React.cache(), bundle optimization, and secure Server Actions.
When to Use
Activate whenever building, refactoring, or reviewing Next.js pages, layouts, Route Handlers (app/api), Server Actions, or components in the app/ directory.
Negative Constraints (What NOT to Do)
- NEVER use barrel imports for UI libraries: Avoid
import { Button, Dialog } from '@/components'. Import directly from the exact file (import { Button } from '@/components/ui/button') to prevent bundler tree-shaking failures and trace bloat. - NEVER trust client-provided data or session state in Server Actions: Always authenticate session and authorize tenant ownership inside the Server Action handler itself before mutating data.
- NEVER introduce sequential
awaitwaterfalls for independent data: Always usePromise.all()or parallel streaming<Suspense>boundaries. - NEVER pass large unneeded serialized data from Server to Client Components: Only pass the specific primitive fields required by the client component (
server-dedup-props). - NEVER use
useEffectfor data fetching: Fetch directly in Server Components or use TanStack Query / SWR for client-side queries. - NEVER import server-only modules in client components: Use the
server-onlypackage in data access layers to catch accidental client imports at build time.
Rules & Patterns
1. Eliminating Async Waterfalls (Critical)
- Parallel Fetching: Fetch independent data concurrently at the top of the route or component.
- Granular Streaming: Wrap slow, non-critical subtrees in
<Suspense fallback={<Skeleton />}>so critical above-the-fold content streams immediately. - Defer Awaits: Check cheap synchronous conditions before awaiting remote resources.
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.
- 3d ago First seen · 124 lines · 0 tokens per session scan A 3bc74b0e412c
nextjs is a cursor rule published in the GitHub repository kok-o/koko-contextos-agents (2 stars, last pushed 3d ago), licensed MIT. It costs nothing until one of its globs matches a file; then it loads 1,130 tokens. 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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index
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Applies general TypeScript best practices and style guidelines to all TypeScript files in the project.
readme-best-practices
README Best Practices - enforces high-quality README patterns when creating or editing README files.