Solo contract

Solo accepts a constrained subset of Astro. This page documents exactly what is and isn't supported in v1.

Pages

Pages in src/pages/** must follow explicit composition rules.

Accepted:

• Explicit imports
• Component composition with literal props
• Exactly one layout per page
• Deterministic components — same input, same output
• Static HTML

Rejected:

• Business logic in page frontmatter
• Dynamic layout selection
• Runtime Astro features (client:*, islands)
• Arbitrary JS computation in frontmatter (sort, filter, Object.values, new Date)
• Markdown pages (.md) — use .astro pages only

Layouts

Layouts in src/layouts/**.

Accepted:

• Multiple layouts in the project
• Exactly one layout per page
• Static, explicit layout composition

Rejected:

• Nested layouts (a layout that composes another layout)
• Dynamic layout selection

Props

Solo v1 accepts literal props only.

Accepted types:

• string
• number
• boolean
• null

// ✓ Accepted
<Hero headline="Hello Solo" />
<CTA title="Contact" buttonHref="/contact/" />
<Card price={89.99} featured={true} />

// ✕ Rejected — error E201
<Hero headline={page.title} />
<CTA title={site.cta.title} />
<Hero headline={"Hello " + name} />

CSS

Accepted:

• Global CSS files
• Global SCSS compiled by Astro (import "../styles/styles.scss" in the layout)
• Inline style="" attributes
• <link rel="stylesheet"> tags

Rejected — error E230:

• Component <style> blocks (scoped CSS)
• CSS modules
• Astro's local component styling pipeline

Images

Accepted:

• Static images in public/images/ — referenced as /images/photo.jpg
• Absolute external URLs

Out of scope:

• Astro's image optimization pipeline (<Image />, <Picture />)
• Responsive image generation
• Complex asset manifests

Framework components

React, Vue, and Svelte components present in the project are skipped — not compiled, not rejected as errors.

They generate a placeholder in the output:

<div
  data-fm-skipped="react"
  data-fm-component="FancyWidget"
  data-fm-source="src/components/FancyWidget.tsx"
  data-fm-props='{"productId":"abc"}'
></div>

And an entry in manifest.json. In --strict mode, framework components become blocking errors.

Blessed components

The following components are explicitly supported via an allowlist — not via a generic engine:

• SEOPage, SEOWebsite, SEOArticle, SEOOrganisation, SEOLocalBusiness
• RichText

Components not on the allowlist and not yet supported trigger error E271.