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/thesethrose/devrules/astro4git clone --depth 1 https://github.com/TheSethRose/DevRulesWhat 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 | $0.01018 |
| Opus 5 | $0.00000 | $0.00509 |
| Sonnet 5 | $0.00000 | $0.00204 |
| Haiku 4.5 | $0.00000 | $0.00102 |
Grade A, and why
Astro4 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 2d 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 — 65 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Astro Development Best Practices (v4+)
You are an expert Astro developer, aware of its features up to version 4+. Reference: https://docs.astro.build/en/getting-started/
Core Concepts
- Component-Based: Uses
.astrofiles blending HTML, scoped CSS, and JS/TS frontmatter. - Islands Architecture: Zero-JS by default. Use
client:*directives (load,idle,visible,media,only) to hydrate interactive UI components (Islands) client-side. - UI Framework Agnostic: Integrates with React, Vue, Svelte, Solid, Preact, Alpine.js, etc.
- Content-Focused: Built-in Content Collections API for type-safe Markdown/MDX. Astro DB for integrated database solutions.
- Server-First: Prioritizes Server-Side Rendering (SSR) via Adapters or Static Site Generation (SSG).
- View Transitions: Built-in support for smooth page transitions and persistent elements using
astro:transitions.
Project Structure (Typical)
src/pages/: File-based routing (.astro,.md,.mdx,.js,.tsfor API routes).src/layouts/: Reusable page layout components (.astro).src/components/: Reusable UI components (.astroor framework components).src/content/: Content Collections (config.ts,posts/,docs/, etc.).src/styles/: Global CSS, fonts.src/middleware.{ts,js}: For executing code before/after rendering (auth, redirects).src/env.d.ts: TypeScript definitions for Astro environment.public/: Static assets.astro.config.mjs(or.ts): Main configuration.db/config.ts,db/seed.ts: Astro DB configuration and seeding.
Configuration (astro.config.mjs)
- Define
site,base, output mode (static/server/hybrid). - Configure Integrations: UI Frameworks (
@astrojs/react, etc.), Tailwind (@astrojs/tailwind), MDX (@astrojs/mdx), Sitemap (@astrojs/sitemap), Astro DB (@astrojs/db). - Setup Adapters for deployment (Vercel, Netlify, Cloudflare, Node).
- Define Vite plugin options.
- Manage TypeScript settings.
- Configure Markdown/MDX options (syntax highlighting, remark/rehype plugins).
- Set up Internationalization (i18n) routing.
- Enable Experimental Features.
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.
- 2d ago First seen · 65 lines · 0 tokens per session scan A 0e1d93f7d264
Astro4 is a cursor rule published in the GitHub repository TheSethRose/DevRules (25 stars, last pushed 1y ago), licensed MIT. It costs nothing until one of its globs matches a file; then it loads 1,018 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 2026-08-30.
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