Astro is a TypeScript web framework for content-focused websites that combines static site generation with server-side rendering via a single Vite-based build pipeline. It compiles .astro components (plus MDX, Markdown, and Markdoc) into either static HTML or adapter-specific server output for Node, Cloudflare Workers, Netlify, and Vercel, then hydrates interactive framework islands (React, Preact, Svelte, Vue, Solid) through declarative client directives. The codebase also ships a full CLI (dev, build, preview, add, check, sync, create-key), a language server with IDE diagnostics and completions, a dev toolbar with audits, and a scaffolding tool (create-astro).

Starlight is a production-grade documentation framework built as an Astro integration. It transforms Markdown/MDX content collections into fully-featured documentation sites with i18n, sidebar navigation, table of contents, search (Pagefind or DocSearch), expressive code blocks, and a rich component library (aside, badge, card, tabs, file tree, steps, etc.). The architecture follows a plugin system with lifecycle hooks (`config:setup`, `i18n:setup`) and supports component overrides via virtual modules, allowing deep customization without forking. The core package (`@astrojs/starlight`) handles route generation, Markdown processing (via unified or the custom Sätteri engine), CSS layer management, and head tag optimization. Official plugins add Tailwind CSS support, Algolia DocSearch, and a Markdoc preset. The codebase emphasizes accessibility, performance (minimal client JS, CSS cascade layers), and internationalization with 30+ translation files for UI strings and content fallback per locale. A comprehensive test suite (Vitest unit tests, Playwright e2e, accessibility audits) and automated CI/CD (changesets, preview releases) maintain reliability.