sveltekit

SvelteKit

Optimize for route and data flows that stay correct under SSR, hydration, navigation, and progressive enhancement. Focus on boundaries and the shortest correct implementation.

Scope

Use this skill when the hard part is app-level or route-level behavior. If the task is mostly about component internals, runes, snippets, local state, or styling, use the svelte skill.

Workflow

1. Establish the local style before changing code.

   • Inspect package.json, svelte.config.*, the route tree, hooks, and nearby route files.
   • Prefer existing conventions in touched files unless the task is an explicit migration.
   • For new code, default to current SvelteKit APIs and typed route files.

2. Choose the server/client boundary before writing code.

   • Put server-only work in +page.server.*, +layout.server.*, +server.*, hooks, or $lib/server/*.
   • Put reusable view logic in components or $lib, not route files.
   • Keep request-specific mutable state out of shared modules so server state cannot leak across users.
   • Keep route flow obvious: params, URL, cookies, and locals -> load or action -> typed props -> component.

3. Solve data flow before UI details.

   • Decide whether truth belongs in the URL, server data, component state, snapshots, context, or a shared reactive object.
   • Derive state instead of synchronizing copies.
   • Decide whether data reruns automatically or only after targeted invalidation.

4. Make navigation and SSR behavior explicit.

   • Check whether code runs on the server, in the browser, or both.
   • Decide whether state survives reloads, deep links, history navigation, or only the current render.
   • Check whether route components are reused across navigation and whether anything must reset explicitly.

5. Validate the relevant server, browser, and progressively enhanced paths with the repository's existing checks.

   • When behavior is version-sensitive, verify it against the installed Svelte and SvelteKit versions and current official documentation.

Topic guides

• When changing route files, load, parent data, dependency tracking, or serialization, read guides/load-routing.md.
• When implementing a form, mutation, progressive enhancement, or API endpoint, read guides/forms-endpoints.md.
• When handling hooks, authentication, cookies, secrets, or request-local identity, read guides/auth-cookies.md.
• When placing state or changing navigation, invalidation, history, or reset behavior, read guides/state-navigation.md.
• When browser-only code, server rendering, hydration, or pre-hydration interaction is involved, read guides/ssr-hydration.md.
• When adopting renamed APIs or another version-sensitive SvelteKit feature, read guides/migration.md.