TL;DR

SvelteKit 3.0 introduces significant breaking changes to project structure, including a new #lib alias and stricter server-only directory enforcement.

Breaking

• Replace $lib alias with #lib and remove files.lib config.
• Server-only directories (/server/) are now treated as server-only globally (excluding src/routes and assets).
• handle's resolve must now return a Promise.
• getRequest and setResponse are now synchronous.
• page.url is now immutable at the type level.
• invalidateAll is deprecated in favor of refreshAll.
• defineEnvVars moved to @sveltejs/kit/env.
• Cross-origin form submissions now require a Content-Type header.
• experimental.handleRenderingErrors flag removed.
• CORS handling for static directory requests is now delegated to Vite during development.

New

• Support for hyphens in parameter and matcher names.
• Added ErrorProps to generated types.
• Import aliases are now transformed into relative imports in files.

Fixes Worth Knowing

• Fixed CSRF protection to enable in non-production NODE_ENV builds.
• Resolved an issue where client-side code was incorrectly bundled by Cloudflare Wrangler.
• Fixed <svelte:boundary> to properly reset on client navigation.

Before You Upgrade

• Update all $lib imports to #lib.
• Update handle hooks to ensure resolve returns a Promise.
• Migrate invalidateAll calls to refreshAll.

TL;DR

Documentation for @sveltejs/enhanced-img has been updated to use the correct library alias.

TL;DR

This update ensures compatibility between adapter-node and SvelteKit 3 prereleases while fixing critical build issues on Windows.

Fixes Worth Knowing

• Resolved an issue where entrypoints (the main files that start the app) were not bundling correctly on Windows.
• Fixed peer dependency conflicts to allow SvelteKit 3 prerelease versions to be used.

TL;DR

SvelteKit has improved environment variable organization and strengthened security for non-production builds.

Breaking

• defineEnvVars has moved to @sveltejs/kit/env (utility for type-safe environment variables).

Fixes Worth Knowing

• CSRF protection is now active in builds where NODE_ENV is not set to production.
• CSS URL references are now correctly absolute when paths.relative is disabled.
• Improved type generation for destructured load and actions exports.
• Updated MAX_COOKIE_SIZE to comply with RFC 6265bis (standard for HTTP state management).

Before You Upgrade

• Update your imports for defineEnvVars to use the new @sveltejs/kit/env path.

TL;DR

SvelteKit now correctly supports using pre-release versions of SvelteKit 3, ensuring compatibility as you upgrade to the latest features.

Fixes Worth Knowing

The adapters for Cloudflare and Auto now correctly handle peer dependencies when using pre-release versions of SvelteKit 3. This resolves potential installation or runtime issues when working with the latest SvelteKit development builds.

TL;DR

SvelteKit 3.0.0-next.8 is now compatible with pre-release versions of itself, resolving dependency issues when using the latest development builds.

Fixes Worth Knowing

Adapters for Vercel and Netlify have been updated to ensure necessary files are included in published packages, preventing potential deployment errors.

Before You Upgrade

No specific action is needed, but ensure you are using the latest versions of @sveltejs/adapter-vercel and @sveltejs/adapter-netlify alongside SvelteKit 3.0.0-next.8 for optimal compatibility.

TL;DR

SvelteKit now supports pre-release versions of SvelteKit 3, resolving compatibility issues for developers working with the latest SvelteKit features.

Fixes Worth Knowing

SvelteKit now correctly handles peer dependencies when using pre-release versions of SvelteKit 3, preventing potential installation or runtime errors. (Peer dependencies: external packages required by a project)

TL;DR

SvelteKit now correctly disables buffering for server-sent events (streaming data) when using reverse proxies like Nginx, improving real-time application responsiveness.

Fixes Worth Knowing

• Server-sent events now stream without buffering when used with common reverse proxies.
• Socket file management was improved to prevent errors on startup.