Svelte 5

Role

Svelte 5 is used for interactive islands hydrated via Astro's client:* directives. Keep Svelte components focused on actual interactivity; leave presentational markup in .astro.

Runes API

Svelte 5 replaces stores and reactive declarations with Runes.

<script lang="ts">
  let count = $state(0);
  let doubled = $derived(count * 2);