Astro Operations Skill | Agent Skills

Astro Operations

Facts verified as of 2026-07.

Comprehensive patterns for Astro framework development: islands architecture, content collections, rendering strategies, view transitions, and multi-platform deployment.

Rendering Strategy Decision Tree

Which rendering strategy?
│
├─ Is content mostly static (blog, docs, marketing)?
│  ├─ YES → Does it change less than daily?
│  │  ├─ YES → SSG (output: 'static')
│  │  │        Fastest TTFB, CDN-cacheable, zero runtime cost
│  │  └─ NO  → Hybrid (output: 'hybrid')
│  │           Default static + opt-in SSR per route
│  └─ NO  → Does every page need personalization?
│     ├─ YES → SSR (output: 'server')
│     │        Dynamic per-request, auth-aware, real-time data
│     └─ NO  → Hybrid (output: 'hybrid')
│              Static shell + server islands for dynamic parts
│
├─ Does the app need real-time interactivity (dashboard, SPA)?
│  ├─ YES → Is it a full SPA with client-side routing?
│  │  ├─ YES → Consider React/Vue SPA instead, or Astro + client:only
│  │  └─ NO  → Hybrid + islands architecture
│  │           Interactive islands in static pages
│  └─ NO  → SSG (output: 'static')
│
├─ Build time concerns (>10k pages)?
│  ├─ YES → Hybrid with on-demand rendering
│  │        Prerender popular pages, SSR the long tail
│  └─ NO  → SSG handles it fine
│
└─ Need edge computing (low latency globally)?
   ├─ YES → SSR + Cloudflare/Vercel Edge adapter
   └─ NO  → SSR + Node adapter or SSG

Configuration

// astro.config.mjs
import { defineConfig } from 'astro/config';

// SSG (default) - all pages prerendered at build time
export default defineConfig({
  output: 'static',
});

// SSR - all pages rendered on request
export default defineConfig({
  output: 'server',
  adapter: cloudflare(), // or vercel(), netlify(), node()
});

// Hybrid - static default, opt-in SSR per page
export default defineConfig({
  output: 'hybrid',
  adapter: cloudflare(),
});

---
// In hybrid mode, opt OUT of prerendering for specific pages:
export const prerender = false;
// In SSR mode, opt IN to prerendering:
export const prerender = true;
---

Islands Architecture Quick Reference

| Directive | Hydrates When | JS Shipped | Use Case | |-----------|--------------|------------|----------| | client:load | Immediately on page load | Full bundle | Above-fold interactive (nav, hero CTA) | | client:idle | After page is idle (requestIdleCallback) | Full bundle | Below-fold interactive (comment form, chat) | | client:visible | When scrolled into viewport | Full bundle | Far-down-page (footer widget, carousel) | | client:media | When media query matches | Full bundle | Mobile-only nav, responsive components | | client:only="react" | Immediately, skip SSR entirely | Full bundle | Components that can't SSR (canvas, WebGL) | | (none) | Never - static HTML only | Zero JS | Static content, cards, headers |

---
import NavBar from '../components/NavBar.tsx';
import CommentForm from '../components/CommentForm.tsx';
import ImageCarousel from '../components/ImageCarousel.svelte';
import MobileMenu from '../components/MobileMenu.vue';
import ThreeScene from '../components/ThreeScene.tsx';
---

<!-- Loads immediately - critical interactivity -->
<NavBar client:load />

<!-- Loads after page is idle - non-critical -->
<CommentForm client:idle />

<!-- Loads when scrolled into view - lazy -->
<ImageCarousel client:visible />

<!-- Loads only on mobile -->
<MobileMenu client:media="(max-width: 768px)" />

<!-- Client-only, no SSR (WebGL can't run on server) -->
<ThreeScene client:only="react" />

Content Collections Quick Start

Define Schema

// src/content.config.ts (Astro 5) or src/content/config.ts (Astro 4)
import { defineCollection, z, reference } from 'astro:content';
import { glob } from 'astro/loaders';

const blog = defineCollection({
  loader: glob({ pattern: '**/*.{md,mdx}', base: './src/content/blog' }),
  schema: z.object({
    title: z.string(),
    description: z.string().max(160),
    pubDate: z.coerce.date(),
    updatedDate: z.coerce.date().optional(),
    heroImage: z.string().optional(),
    tags: z.array(z.string()).default([]),
    draft: z.boolean().default(false),
    author: reference('authors'), // Reference another collection
  }),
});

const authors = defineCollection({
  loader: glob({ pattern: '**/*.json', base: './src/content/authors' }),
  schema: z.object({
    name: z.string(),
    avatar: z.string(),
    bio: z.string(),
    socials: z.object({
      twitter: z.string().optional(),
      github: z.string().optional(),
    }).optional(),
  }),
});

export const collections = { blog, authors };

Query Collections

---
import { getCollection, getEntry } from 'astro:content';

// Get all non-draft blog posts, sorted by date
const posts = (await getCollection('blog', ({ data }) => !data.draft))
  .sort((a, b) => b.data.pubDate.valueOf() - a.data.pubDate.valueOf());

// Get a single entry
const post = await getEntry('blog', 'my-first-post');

// Resolve a reference
const author = await getEntry(post.data.author);

// Render content
const { Content, headings } = await post.render();
---

<Content />

Content Collections vs External CMS

| Criterion | Content Collections | External CMS (Payload, etc.) | |-----------|--------------------|-----------------------------| | Content type | Local markdown/MDX, docs, blogs | Relational data models | | Authors | Developers (version-controlled) | Editors (admin UI, multi-user auth) | | Validation | Type-safe via Zod at build time | CMS-side schemas + API contracts | | Update cadence | Deploys with the site | Independent of deployments | | API needs | None (build-time queries) | REST/GraphQL for other consumers | | Workflow | Git PRs, simple review | Editorial workflows, drafts, roles |

Rule of thumb: start with Content Collections; reach for a CMS only when non-developers need to publish without a deploy, or when content is genuinely relational.

Project Structure Reference

project-root/
├── astro.config.mjs          # Astro configuration
├── tsconfig.json              # TypeScript config (extends astro/tsconfigs)
├── package.json
├── public/                    # Static assets (copied as-is)
│   ├── favicon.svg
│   ├── robots.txt
│   └── og-image.png
├── src/
│   ├── pages/                 # File-based routing
│   │   ├── index.astro        # → /
│   │   ├── about.astro        # → /about
│   │   ├── blog/
│   │   │   ├── index.astro    # → /blog
│   │   │   └── [slug].astro   # → /blog/:slug (dynamic)
│   │   ├── api/
│   │   │   └── search.ts      # → /api/search (API endpoint)
│   │   └── [...slug].astro    # → catch-all/404
│   ├── layouts/
│   │   ├── BaseLayout.astro   # HTML shell, <head>, global styles
│   │   └── BlogPost.astro     # Blog post layout
│   ├── components/
│   │   ├── Header.astro       # Static Astro component
│   │   ├── Footer.astro
│   │   ├── NavBar.tsx         # React island
│   │   └── Counter.svelte     # Svelte island
│   ├── content/               # Content collections source files
│   │   ├── blog/
│   │   │   ├── post-one.md
│   │   │   └── post-two.mdx
│   │   └── authors/
│   │       └── jane.json
│   ├── content.config.ts      # Collection schemas (Astro 5)
│   ├── middleware.ts           # Request/response middleware
│   ├── styles/
│   │   └── global.css
│   └── lib/                   # Shared utilities
│       ├── utils.ts
│       └── constants.ts
└── .env                       # Environment variables

View Transitions Quick Reference

---
// src/layouts/BaseLayout.astro
import { ViewTransitions } from 'astro:transitions';
---

<html>
  <head>
    <ViewTransitions />
  </head>
  <body>
    <slot />
  </body>
</html>

Transition Directives

<!-- Persist element across pages (keeps state, avoids re-render) -->
<audio transition:persist id="player">
  <source src="/music.mp3" />
</audio>

<!-- Named transition for animation pairing -->
<img transition:name="hero" src={post.heroImage} />

<!-- Custom animation -->
<div transition:animate="slide">Content</div>
<div transition:animate="fade">Content</div>
<div transition:animate="none">No animation</div>

<!-- Persist with name (for multiple persistent elements) -->
<video transition:persist="media-player" />

Lifecycle Events

<script>
  document.addEventListener('astro:before-preparation', (e) => {
    // Before new page is fetched - cancel navigation, show loading
  });

  document.addEventListener('astro:after-preparation', (e) => {
    // New page fetched, before swap
  });

  document.addEventListener('astro:before-swap', (e) => {
    // Customize DOM swap behavior
  });

  document.addEventListener('astro:after-swap', () => {
    // DOM updated - reinitialize scripts
  });

  document.addEventListener('astro:page-load', () => {
    // Page fully loaded (fires on initial + every navigation)
    // Use this instead of DOMContentLoaded with View Transitions
  });
</script>

Back/Forward Handling

// astro.config.mjs
export default defineConfig({
  prefetch: {
    prefetchAll: true,         // Prefetch all links on hover
    defaultStrategy: 'hover',  // 'hover' | 'tap' | 'viewport' | 'load'
  },
});

<!-- Per-link prefetch control -->
<a href="/about" data-astro-prefetch>Prefetch on hover (default)</a>
<a href="/blog" data-astro-prefetch="viewport">Prefetch when visible</a>
<a href="/contact" data-astro-prefetch="load">Prefetch immediately</a>
<a href="/external" data-astro-prefetch="false">No prefetch</a>

Deployment Decision Tree

Where to deploy?
│
├─ Need edge computing + Cloudflare ecosystem (KV, D1, R2)?
│  └─ Cloudflare Pages/Workers
│     Adapter: @astrojs/cloudflare
│     Best for: Global edge, Workers bindings, cost-effective
│
├─ Need serverless + Vercel ecosystem (ISR, analytics)?
│  └─ Vercel
│     Adapter: @astrojs/vercel
│     Best for: Next.js migration, image optimization, ISR
│
├─ Need serverless + Netlify ecosystem (forms, identity)?
│  └─ Netlify
│     Adapter: @astrojs/netlify
│     Best for: JAMstack, built-in forms, split testing
│
├─ Need full server control (Docker, custom runtime)?
│  └─ Node.js (standalone or Express/Fastify)
│     Adapter: @astrojs/node
│     Best for: Self-hosted, WebSocket, long-running processes
│
└─ Pure static site (no SSR needed)?
   └─ Any static host (GitHub Pages, S3, Cloudflare Pages)
      No adapter needed, output: 'static'
      Best for: Blogs, docs, marketing sites

Adapter Installation

# Cloudflare
npx astro add cloudflare

# Vercel
npx astro add vercel

# Netlify
npx astro add netlify

# Node.js
npx astro add node

Common Gotchas

| Gotcha | Why | Fix | |--------|-----|-----| | Hydration mismatch errors | Server HTML differs from client render (dates, random IDs, browser APIs) | Use client:only for browser-dependent components, or ensure deterministic rendering | | import.meta.env undefined in client | Only PUBLIC_ prefixed vars are exposed to client-side code | Rename to PUBLIC_MY_VAR or pass via props from server | | Dynamic routes 404 in SSG | getStaticPaths() not returning all possible params | Ensure getStaticPaths() returns every valid path, or switch to hybrid/SSR | | Images not optimizing | Using <img> instead of Astro's <Image /> component | Import from astro:assets: import { Image } from 'astro:assets' and use local imports for src | | SSR fails without adapter | output: 'server' or 'hybrid' requires a deployment adapter | Install adapter: npx astro add cloudflare (or vercel, netlify, node) | | MDX components not rendering | Custom components not passed to MDX content | Pass components via <Content components={{ MyComponent }} /> or use astro.config.mjs MDX config | | Content collection schema changes not reflected | Type generation is cached, stale .astro types | Run astro sync to regenerate types, restart dev server | | client:* on Astro components | Client directives only work on framework components (React, Vue, Svelte) | Astro components are static-only; extract interactive parts to a framework component | | document / window is not defined | Server-side code cannot access browser globals | Guard with if (typeof window !== 'undefined') or move to client:only | | Styles leaking between components | Using global CSS instead of scoped styles | Use <style> (scoped by default in .astro) or <style is:global> intentionally | | View Transitions break scripts | DOMContentLoaded only fires once with View Transitions | Use astro:page-load event instead, which fires on every navigation | | Env vars missing in production | .env not loaded or platform env vars not configured | Use envField in astro.config.mjs for validation; set vars in platform dashboard |

Production Security Checklist

For every production deployment, address:

CSP headers - configure a restrictive Content-Security-Policy (see middleware patterns in references/deployment.md)
Remote image restrictions - enforce explicit image.domains / remotePatterns allow-lists; never derive image URLs from user input (SSRF risk)
Host header validation - verify the request host matches expected domains in middleware (SSR/hybrid only)
Secrets management - on Cloudflare, use Workers Bindings (wrangler secret put), not env vars baked into code; elsewhere use platform secret stores
HTTPS only - ensure all external resources (scripts, images, fonts) load over HTTPS
Input validation - sanitize all user input in SSR contexts (query params, form bodies, cookies)

Reference Files

| File | Contents | Lines | |------|----------|-------| | references/content-collections.md | Schema patterns, Zod types, querying, MDX, content layer API, migrations | ~500 | | references/islands-rendering.md | Islands deep dive, client directives, framework integration, server islands | ~550 | | references/deployment.md | Cloudflare/Vercel/Netlify/Node adapters, env vars, optimization | ~500 |

Agent Skills: Astro Operations

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