What's new in Svelte: September 2026

Svelte 5.57 shipped with new SvelteMap methods, including getOrInsert and getOrInsertComputed, while SvelteKit 3 advanced to Release Candidate with features like enhanced cross-page form actions and a new QUERY HTTP method handler. The sv CLI introduced an ai-tools add-on replacing the mcp one, and sv@next now offers a task-based sveltekit-3 migration for existing apps.

What’s new in Svelte: September 2026 New SvelteMap methods in Svelte 5.57, more SvelteKit 3 iteration and sv 1.0 previews SvelteKit 3 migrations This month, Svelte 5.57 shipped with new SvelteMap methods and a few quality-of-life additions while SvelteKit 3 got closer to the finish line with its Release Candidate. The sv CLI also got a new ai-tools add-on that replaces the old mcp one, and sv@next now ships a task-based sveltekit-3 migration for existing apps. Let’s dive a bit deeper What’s new in Svelte SvelteMap now has getOrInsert and getOrInsertComputed methods for the common “read or initialize” pattern 5.57.0 , Docs https://svelte.dev/docs/svelte/svelte-reactivity SvelteMap , 18728 https://github.com/sveltejs/svelte/pull/18728 createContext now returns a third has function so you can check whether a context has been set without triggering the get error 5.57.0 , Docs https://svelte.dev/docs/svelte/context , 18472 https://github.com/sveltejs/svelte/pull/18472 <select now supports the defaultValue attribute, so the select reverts to that value on form reset 5.57.0 , 18591 https://github.com/sveltejs/svelte/pull/18591 svelte/server now exports the RenderOutput , SyncRenderOutput , Csp and Sha256Source types for typing server render output and CSP sources 5.57.0 , 18648 https://github.com/sveltejs/svelte/pull/18648 For the full list of patches and bug fixes, see the Svelte CHANGELOG https://github.com/sveltejs/svelte/blob/main/packages/svelte/CHANGELOG.md . What’s new in SvelteKit 3’s RC Prereleases have kept rolling on the @next line this month, adding a few more features and refining the surface: - Enhanced cross-page form actions now navigate to the action page on success and failure, matching native form behavior 3.0.0-next.17 , breaking, 16684 https://github.com/sveltejs/kit/pull/16684 - Adapter Vite plugins can now be split into pre and post groups so adapters can run transforms at the right point in the pipeline 3.0.0-next.18 , breaking, 16711 https://github.com/sveltejs/kit/pull/16711 - Files with + prefixes are now ignored during routing if their names contain test , spec or stories , so colocated tests don’t accidentally become routes 3.0.0-next.19 , 16715 https://github.com/sveltejs/kit/pull/16715 - Development-server response logging is now nicer to read and routes through Vite’s logger so it respects logLevel and customLogger 3.0.0-next.20/25 , 16744 https://github.com/sveltejs/kit/pull/16744 , 16858 https://github.com/sveltejs/kit/pull/16858 defineParams and the associated types have moved to @sveltejs/kit/params 3.0.0-next.19 , breaking, 16716 https://github.com/sveltejs/kit/pull/16716 +server.js files can now export a QUERY HTTP method handler 3.0.0-next.24 , 16782 https://github.com/sveltejs/kit/pull/16782 - The preload filter for fonts now receives the project-relative source filename so you can filter by directory or component 3.0.0-next.24 , 16443 https://github.com/sveltejs/kit/pull/16443 - Adapters can call the new applyReroute helper for split serverless function deployments 3.0.0-next.25 , 16665 https://github.com/sveltejs/kit/pull/16665 For the meantime, all of the SvelteKit 3 docs live on next.svelte.dev https://next.svelte.dev/docs/kit/migrating-to-sveltekit-3 , and the full changelog is on the version-3 branch https://github.com/sveltejs/kit/blob/version-3/packages/kit/CHANGELOG.md . The stable 2.x line kept moving too with three patch releases 2.70.1 , 2.70.2 , 2.70.3 - see the SvelteKit CHANGELOGs https://github.com/sveltejs/kit/tree/main/packages for the details. What’s new in the Svelte CLI and Language Tools - The mcp add-on has been replaced with a broader ai-tools add-on that can set up the Svelte plugin Claude Code, opencode or pick individual tools MCP server, skills, sub-agents per client sv@0.17.0 , Docs https://svelte.dev/docs/cli/ai-tools , 1050 https://github.com/sveltejs/cli/pull/1050 @sveltejs/sv-utils picks up isKit3 , resolveLibPrefix and libSubpathImports helpers so add-ons can transparently handle SvelteKit 2 and 3 sv-utils@0.3.3 , 1199 https://github.com/sveltejs/cli/pull/1199 sv migrate has been reworked to prepare for the SvelteKit 3 migration - it now lists tasks, ships a sveltekit-3 task that bumps dependencies and rewrites $lib to lib , adds an $app/state task, delegates the older migrations to svelte-migrate@1 , and creates a list of changes a developer or agent should resolve if they cannot be migrated automatically sv@1.0.0-next.0 , Docs https://svelte.dev/docs/cli/sv-migrate , 1138 https://github.com/sveltejs/cli/pull/1138 , 1241 https://github.com/sveltejs/cli/pull/1241 , 1249 https://github.com/sveltejs/cli/pull/1249 - Newly created projects use lib Node subpath imports instead of $lib , matching SvelteKit 3 sv@1.0.0-next.0 , 1185 https://github.com/sveltejs/cli/pull/1185 - Community add-ons no longer require a scoped package name sv@1.0.0-next.4 , 1216 https://github.com/sveltejs/cli/pull/1216 - The experimental add-on is now scoped to enabling experimental features, and the versions option value was renamed to kit-3 sv@1.0.0-next.0 , breaking, 1241 https://github.com/sveltejs/cli/pull/1241 , 1185 https://github.com/sveltejs/cli/pull/1185 - Vite plugin gets a dynamicCompileOptions argument for the current Vite environment, useful when you want to compile differently for the client, server or SSR environment vite-plugin-svelte@7.3.0 , 1386 https://github.com/sveltejs/vite-plugin-svelte/pull/1386 svelte2tsx and svelte-check learn about SvelteKit 3’s flattened config structure so the type generation and diagnostics keep working through the migration svelte-check@4.7.6/svelte2tsx@0.7.61/svelte-language-server@0.18.4 , 3104 https://github.com/sveltejs/language-tools/pull/3104 , 3106 https://github.com/sveltejs/language-tools/pull/3106 Want to dive deeper? Check out the Svelte CLI https://github.com/sveltejs/cli/releases , language-tools https://github.com/sveltejs/language-tools/releases and ai-tools https://github.com/sveltejs/ai-tools/releases releases. Community Showcase Apps & Sites built with Svelte EdenText https://edentext.app is a fully local open-source word processor for .odt and .docx documents that runs entirely in the browser or as a PWA Kraa.io https://kraa.io is a minimal-interface text editor and publishing platform where you can instantly make your writing public Note by Note https://chromewebstore.google.com/detail/note-by-note-%E2%99%AA-pitch-shif/bifddjdeacijlelkenjkfcmlbicgoglc is a browser extension for musicians that transposes, slows down and removes vocals from YouTube videos in real time GitHub https://github.com/patrickiel/note-by-note Roomy https://a.weird.one/ is an AT Protocol-based Discord alternative for group chats in the Atmosphere Taxing Wages https://taxing-wages.gokberk.se is a salary tax calculator for 32 OECD countries built on the OECD’s taxing wages data Learning Resources This Week in Svelte To Read Tested SvelteKit on Cloudflare. Oooooh boy... https://www.reddit.com/r/sveltejs/comments/1vr2hxe/tested sveltekit on cloudflare oooooh boy/ is a write-up on porting a full app to SvelteKit + Cloudflare Workers + KV + D1 + Hyperdrive + Better Auth and coming away impressed Libraries, Tools & Components UI Components and Design Systems Svelte DataTables Components https://sv-table.vercel.app is a free collection of 16 data-table components and 11 pre-built table blocks on top of TanStack Table v9, installable via the shadcn-svelte CLI Svelte Fancy Components https://sv-animations.vercel.app/fancy is a port of Fancy Components with 14 unique text and media effects like Scramble In, Letter Swap and Pixel Trail SVAR Svelte Calendar and Kanban https://svar.dev/svelte/calendar/ add event calendar and Kanban board components to the SVAR Svelte library, both with drag and drop, filtering and iCal import/export MUKADE UI https://mukade-ui.com is a terminal-style UI component library Material Svelte https://material-svelte.flenze.com is a Material Design 3-inspired UI library Beautiful UI Svelte https://beautiful-ui-svelte.vercel.app is a port of a set of React AI-app components Animations and Icons morphicons https://morphicons-svelte.vercel.app is an icon library where any stroke icon morphs into any other with a single prop change Amicro SV https://amicro.enisdev.com is a port of Amicro, a curated library of micro-interaction and transition components loadersz https://loadersz.vercel.app is a framework-agnostic loader library with 70 canvas-based motion states, exposed as a custom element with typed entry points for React, Vue and Svelte Frameworks and Dev Tools ogygia https://ogygia.puruvj.dev/ brings SSR islands to SvelteKit, from Svelte contributor Puru VJ https://bsky.app/profile/puruvj.dev TanStack Table v9 https://tanstack.com/table/v9 shipped stable with its first Svelte-native adapter that connects directly to runes, plus Svelte-specific docs and a shadcn-svelte example Wait0 https://github.com/devforth/wait0 is a dynamic cache with SWR warmup and sitemap discovery for SvelteKit that serves pages instantly and revalidates in the background That’s it for this month Let us know if we missed anything on Reddit https://www.reddit.com/r/sveltejs/ or Discord https://discord.gg/svelte . Until next time 👋🏼