Track fontless migration once SvelteKit support lands

[stickerdaniel]

Current state

We use fontaine@^0.8.0 for metric-matched fallback faces on the self-hosted Outfit font, wired up via FontaineTransform.vite() in vite.config.ts:385. This handles CLS: the swap from the system fallback to the real face shifts layout near zero. It works correctly with SvelteKit.

What fontless would bring

fontless is the framework-agnostic successor to fontaine, developed in the same unjs/fontaine repo (Nuxt and Qwik teams together with Daniel Roe). Where fontaine only generates the fallback metrics and leaves font sourcing to us, fontless is the full pipeline as a single Vite plugin:

• Auto-discovery of font-family declarations from CSS, no manual config
• Provider resolution via unifont (Google Fonts, Bunny, Fontshare, Fontsource, local)
• Automatic download and self-hosting of the font files
• @font-face generation
• Plus the same fontaine fallback metrics for CLS

The win for us would be dropping the manual font management (self-hosting, @font-face wiring), not better CLS, since fontaine already covers that.

Blocker

fontless does not support SvelteKit yet, tracked upstream in unjs/fontaine#558. Until that lands, staying on fontaine is correct.

Action

Stay on fontaine. Watch unjs/fontaine#558 and revisit the migration once SvelteKit support ships. When migrating, the FontaineTransform.vite() block in vite.config.ts and the fontaine dependency in package.json are the two touchpoints.

See also: unjs/fontaine#558