Minimal reproduction for a preview-mode leak where Starlight base/reset CSS is attached to / even though Starlight only serves /docs/.

• Astro 6.1.0
• @astrojs/starlight 0.38.2
• @astrojs/cloudflare 13.1.4
• Tailwind CSS v4 via @tailwindcss/vite

bun install
bun run build
bun run preview

Then open:

• http://127.0.0.1:4321/
• http://127.0.0.1:4321/docs/

• / should only load the website stylesheet.
• /docs/ should load the Starlight styles.

• / also loads the shared Starlight stylesheet.
• In the current build, / includes both:
  • /_astro/index@_@astro.CY5fRZ19.css
  • /_astro/index@_@astro.EnuQFs_q.css
• /docs/ includes:
  • /_astro/index@_@astro.EnuQFs_q.css
  • /_astro/print.ehPL0gv-.css

index@_@astro.EnuQFs_q.css contains the Starlight base layer (@layer starlight.base), so it is leaking onto the non-doc page.

The shared website layout imports src/components/Header.astro, and that header imports:

import { getRelativeLocaleUrl } from 'astro:i18n'

Replacing that with a local helper makes the shared Starlight CSS stop appearing on /.