Technology Stack

Core Stack

Framework & Build Tools

Framework:
  name: Astro
  version: 7.4.1
  features:
    - Static Site Generation (SSG) by default
    - Server-Side Rendering (SSR) optional
    - Zero JavaScript by default
    - Content Layer API (content collections)
    - ClientRouter (astro:transitions)
    - Server Islands

Build:
  bundler: Vite 8.2.0
  runtime: Node.js 24.21.0 (>=24.15.0 required)
  package_manager: pnpm 11.27.1 (required)
  typescript: 5.9.3

Styling & Design

CSS:
  framework: Tailwind CSS v4.3.3 (via @tailwindcss/vite plugin)
  approach: Utility-first with design tokens, CSS-first configuration
  features:
    - CSS Variables for theming
    - Container queries support
    - Built-in dark mode (class-based @variant)
    - Oxide engine (no tailwind.config file — configured in CSS via @theme)

Design_Tokens:
  format: JSON → CSS variables (tokens/dist/tokens.css), mapped to utilities via @theme inline
  build: pnpm run tokens:build (scripts/src/build-tokens.ts)
  tools:
    - style-dictionary (optional token generation)

Content & Data

Content:
  format: MDX with Astro Content Collections
  features:
    - Type-safe frontmatter
    - Custom components in content
    - Automatic image optimization
    - Content Layer API for external data

Assets:
  images:
    - Astro <Image> component
    - Sharp for processing
    - Single-format output, AVIF by default (ADR-030; the Image atom's `format` prop overrides)
  fonts:
    - Astro Fonts API with fontProviders.local() (self-hosted woff2 in src/assets/fonts/)
    - Variable fonts preferred, metric-adjusted fallbacks generated automatically

Interactivity (When Needed)

Progressive_Enhancement:
  1. CSS-only solutions (preferred)
  2. ClientRouter from astro:transitions (SPA-like navigation)
  3. Preact Islands (client-side state)

ClientRouter_vs_Islands:
  ClientRouter: For page-level animations and maintaining state across navigation (e.g., persistent audio player). Manages the "frame" of the app.
  Islands: For component-level interactivity that requires client-side JavaScript (e.g., an interactive form). Manages interactive "widgets" on a page.

Island_Directives:
  - client:visible (lazy load)
  - client:idle (load when idle)
  - client:media (responsive loading)
  - client:only (skip SSR)
  Never: client:load (unless justified in ADR)

Development Tools

Code Quality

Linting_Formatting:
  primary: Biome (replaces ESLint + Prettier)
  config: biome.json
  benefits:
    - 20x faster than ESLint
    - Single tool for lint + format
    - Built-in import sorting
    - TypeScript-first

Type_Checking:
  - TypeScript strict mode
  - @astrojs/check for templates
  - Type generation from Content Collections

Git_Hooks:
  tool: Husky + lint-staged
  pre-commit:
    - Format/lint staged code files with Biome (biome check --write)
    - Fix staged Markdown with markdownlint-cli2
  commit-msg:
    - Conventional commits enforced via commitlint
  pre-push:
    - Unit test suite (pnpm run test:unit)
  # Type checking (astro check) runs in quality:ci, not in git hooks

Testing Strategy

Type	Scope	Tool	Where it runs
Unit	Essential (TDD, ADR-037)	Vitest	quality:ci, pre-push hook
E2E	Essential	Playwright (e2e/)	CI
A11y	Essential	axe-core + Playwright (test:a11y)	CI
Performance	Essential	Lighthouse CI (desktop + mobile)	CI, floors 0.90/0.95/0.95/0.90
Mutation	Recommended	Stryker (test:mutate)	Weekly workflow (ADR-042)

Documentation & Component Development

Component_Docs:
  approach: TypeScript interfaces + JSDoc on component props
  features:
    - Props documented at the type level
    - Playwright e2e specs covering key pages (no visual-regression snapshots)
    - "@a11y-tagged accessibility checks in the e2e suite (pnpm run test:a11y)"

API_Docs:
  - TypeScript JSDoc
  - Generated from types
  - Markdown for guides

Deployment & Infrastructure

Hosting

Primary: GitHub Pages
  notes:
    - The starter ships a ready-to-use workflow (.github/workflows/deploy.yml)
    - Base path derived automatically from package.json name
    - Free for public repos

Alternatives:
  - Cloudflare Pages (global CDN, Web Analytics included)
  - Vercel (great DX)
  - Netlify (mature platform)

Performance & Monitoring

Build_Time:
  - Image optimization via Sharp
  - CSS purging via Tailwind
  - Bundle analysis via Vite
  - Compression (Brotli/Gzip)

Runtime:
  shipped: none — the starter includes no analytics or monitoring provider (see Optional Analytics)
  Recommended:
    - Uptime monitoring
    - Core Web Vitals tracking (RUM)
  Advanced:
    - Error tracking with source maps
    - Session replay (privacy-safe)

Package Versions

The starter’s package.json and versions.json are the single source of truth for exact versions — a hardcoded list here would drift. The headline pins: Astro 7.4.1, Tailwind CSS 4.3.3 (via @tailwindcss/vite), Preact 10.29.8, TypeScript 5.9.3, Biome 2.5.15, Vitest 4.1.11, Playwright 1.64.1, plus @astrojs/mdx, @astrojs/sitemap, @astrojs/preact, and Sharp.

Dev tooling includes Husky, lint-staged, Stryker (@stryker-mutator/core for mutation testing), Lighthouse CI 0.15.1, and tsx. Semgrep (SAST) and gitleaks (secret scanning) run in CI via their official containers rather than as devDependencies. Engines require Node >=24.15.0 and pnpm >=10.

Scripts (everyday subset)

{
  "scripts": {
    "dev": "astro dev",
    "build": "pnpm run env:validate && pnpm run tokens:build && astro build",
    "preview": "astro preview",
    "check": "SITE_URL=${SITE_URL:-http://localhost:4321} astro check",
    "format": "biome format . --write",
    "lint": "biome check .",
    "quality:ci": "pnpm run format:check && pnpm run lint && pnpm run lint:md && pnpm run check && pnpm run test:unit && pnpm run agents:check && pnpm run version:check && pnpm run og:check && pnpm run docs:count",
    "tokens:build": "tsx scripts/src/build-tokens.ts",
    "design:validate": "tsx scripts/src/validate-contrast.ts",
    "perf:baseline": "tsx scripts/src/baseline-performance.ts",
    "prepare": "husky"
  }
}

See the starter’s package.json for the full script catalogue (testing, performance gates, maintainer tooling).

Technology Decision Rationale

Why These Choices?

1. Astro 7.4.1: Best-in-class static site generator with minimal JavaScript
2. Tailwind v4: Modern utility CSS with the Oxide engine and CSS-first configuration
3. Biome: Massive speed improvement over ESLint/Prettier
4. Preact: Smaller than React for islands that need state
5. GitHub Pages: Zero-config deploys via the bundled deploy.yml workflow

What We Avoid

• ❌ Multiple build tools (webpack, rollup, etc.)
• ❌ Heavy component frameworks for simple sites
• ❌ Overlapping linters and formatters
• ❌ Client-side routing libraries
• ❌ Large JavaScript frameworks for minimal interactivity
• ❌ External image CDNs (use Astro’s built-in optimization)

Migration Notes

When updating from older versions:

1. Astro 6 → 7: The unified/remark processor is retained for snippet includes (ADR-062); the agent-facing background dev server arrives with dev:agent (ADR-063)
2. Astro 5 → 6: Legacy content collections are gone — use the Content Layer (src/content.config.ts, glob() loaders, entries keyed by .id)
3. Tailwind 3 → 4: Config moves into CSS (@import "tailwindcss" + @theme); the @astrojs/tailwind integration is replaced by @tailwindcss/vite
4. ESLint → Biome: Run migration command: pnpm dlx @biomejs/biome migrate
5. React → Preact: Update imports in island components