--- title: What’s new in Svelte: September 2026 | daily.dev description: Svelte 5.57 adds new SvelteMap methods (getOrInsert, getOrInsertComputed), a createContext has function, select defaultValue support, and new svelte/server... canonical: https://daily.dev/posts/what-s-new-in-svelte-september-2026-tgfowohmb twitter:card: summary_large_image twitter:site: @dailydotdev og:type: website og:site_name: daily.dev og:title: What’s new in Svelte: September 2026 | daily.dev og:description: Svelte 5.57 adds new SvelteMap methods (getOrInsert, getOrInsertComputed), a createContext has function, select defaultValue support, and new svelte/server... og:url: https://daily.dev/posts/what-s-new-in-svelte-september-2026-tgfowohmb og:image: https://api.daily.dev/og/posts/TgfOwohmB.png og:image:alt: What’s new in Svelte: September 2026 og:image:width: 1200 og:image:height: 630 og:locale: en --- > ## Documentation Index > Fetch the complete documentation index at: https://daily.dev/llms.txt > Use this file to discover all available pages before exploring further. # What’s new in Svelte: September 2026 **[Svelte Blog](https://daily.dev/sources/svelte)** · 6 min read · 42 upvotes · 4 comments ## Summary Svelte 5.57 adds new SvelteMap methods (getOrInsert, getOrInsertComputed), a createContext has function, select defaultValue support, and new svelte/server type exports. SvelteKit 3's next release candidate continues iterating with several breaking changes including reworked cross-page form actions, split Vite plugin hooks, defineParams relocation, and route filtering for test files. The sv CLI replaces its mcp add-on with a broader ai-tools add-on and ships a task-based sveltekit-3 migration command that rewrites $lib imports to #lib and bumps dependencies. The roundup also covers stable SvelteKit 2.x patches, language tools updates, and a community showcase of Svelte apps, UI libraries, and dev tools. ## Full article daily.dev links to this article rather than hosting it. Read it at the original source: ## Questions this post answers ### What new methods did SvelteMap get in Svelte 5.57? Svelte 5.57 added getOrInsert and getOrInsertComputed methods to SvelteMap, covering the common read-or-initialize pattern where you fetch a value from a map or create and store it if missing. This avoids manual has/get/set boilerplate that developers previously wrote by hand when working with reactive maps. _Developers tracking Svelte's reactive collection APIs can follow changelog rundowns like this on daily.dev._ ### What breaking changes does SvelteKit 3.0.0-next introduce for form actions and adapters? SvelteKit 3.0.0-next.17 makes cross-page form actions navigate to the action page on both success and failure, matching native form behavior, a breaking change from prior versions. Separately, next.18 lets adapter Vite plugins split into pre and post groups so transforms run at the correct pipeline stage, and next.19 moves defineParams to @sveltejs/kit/params. _Teams planning a SvelteKit 3 upgrade can track breaking changes like these before migrating on daily.dev._ ### What replaced the mcp add-on in the sv CLI? The sv CLI's mcp add-on was replaced by a broader ai-tools add-on in sv@0.17.0, which can set up the Svelte plugin for clients like Claude Code and opencode, or let users pick individual tools such as an MCP server, skills, or sub-agents per client. This gives more granular control over AI tool integration than the previous single add-on. _Developers configuring AI coding tools for Svelte projects can watch tooling shifts like this on daily.dev._ ## Community discussion Top comments from developers on daily.dev. **@vikasganiga05** · 3 upvotes >  **@agustinbarrientos** · 2 upvotes > Try attaching the unautomated-change report to the migration diff and requiring an acknowledgment for every item. Skipped manual steps should stay visible in the pull request even when an agent finishes the import rewrite. **@taiwofrancis** · 1 upvotes > SvelteKit 3 is bringing quite a few changes. I’m more curious to see how smooth that migration actually ends up being. **@igosyee** · 0 upvotes > Remote functions in stable version, when? ## Similar posts on daily.dev - [What’s new in Svelte: November 2025](https://daily.dev/posts/what-s-new-in-svelte-november-2025-jec743u9q) · Svelte Blog · 60 upvotes · 0 comments - [What’s new in Svelte: March 2026](https://daily.dev/posts/what-s-new-in-svelte-march-2026-vhr0vc2mr) · Svelte Blog · 45 upvotes · 0 comments - [What’s new in Svelte: August 2026](https://daily.dev/posts/what-s-new-in-svelte-august-2026-e9ga4akhq) · Svelte Blog · 74 upvotes · 6 comments - [What’s new in Svelte: July 2026](https://daily.dev/posts/what-s-new-in-svelte-july-2026-yjmmqqvqz) · Svelte Blog · 50 upvotes · 4 comments - [What’s new in Svelte: February 2026](https://daily.dev/posts/what-s-new-in-svelte-february-2026-xrzd8do6f) · Svelte Blog · 49 upvotes · 2 comments --- Tags: [#svelte](https://daily.dev/tags/svelte), [#vite](https://daily.dev/tags/vite), [#sveltekit](https://daily.dev/tags/sveltekit) [View this post on daily.dev](https://daily.dev/posts/what-s-new-in-svelte-september-2026-tgfowohmb) ```json {"@context":"https://schema.org","@graph":[{"@type":"Organization","@id":"https://daily.dev/#organization","name":"daily.dev","url":"https://daily.dev","logo":{"@type":"ImageObject","url":"https://daily.dev/apple-touch-icon.png","width":180,"height":180},"sameAs":["https://twitter.com/dailydotdev","https://github.com/dailydotdev","https://www.linkedin.com/company/daily-dev-ltd"]},{"@type":"WebSite","@id":"https://daily.dev/#website","url":"https://daily.dev","name":"daily.dev","publisher":{"@id":"https://daily.dev/#organization"},"potentialAction":{"@type":"SearchAction","target":{"@type":"EntryPoint","urlTemplate":"https://daily.dev/search?q={search_term_string}"},"query-input":"required name=search_term_string"}}]} {"@context":"https://schema.org","@type":"TechArticle","headline":"What’s new in Svelte: September 2026","url":"https://daily.dev/posts/what-s-new-in-svelte-september-2026-tgfowohmb","mainEntityOfPage":{"@type":"WebPage","@id":"https://daily.dev/posts/what-s-new-in-svelte-september-2026-tgfowohmb"},"datePublished":"2026-08-31T20:42:31.522Z","dateModified":"2026-09-14T08:35:11.385Z","description":"Svelte 5.57 adds new SvelteMap methods (getOrInsert, getOrInsertComputed), a createContext has function, select defaultValue support, and new svelte/server...","image":"https://media.daily.dev/image/upload/f_auto,q_auto/v1/posts/c5b7ccf6d988c489a33eb59dd00bc62d?_a=AQAEuop","thumbnailUrl":"https://media.daily.dev/image/upload/f_auto,q_auto/v1/posts/c5b7ccf6d988c489a33eb59dd00bc62d?_a=AQAEuop","isAccessibleForFree":true,"articleSection":"Svelte Blog","inLanguage":"en","publisher":{"@type":"Organization","name":"daily.dev","url":"https://daily.dev","logo":{"@type":"ImageObject","url":"https://daily.dev/apple-touch-icon.png","width":180,"height":180}},"author":{"@type":"Organization","name":"Svelte Blog","logo":"https://media.daily.dev/image/upload/t_logo,f_auto/v1/logos/28300f110fce4397bb4b78124a45ae29","url":"https://daily.dev/sources/svelte"},"commentCount":4,"discussionUrl":"https://daily.dev/posts/what-s-new-in-svelte-september-2026-tgfowohmb","interactionStatistic":[{"@type":"InteractionCounter","interactionType":{"@type":"LikeAction"},"userInteractionCount":42},{"@type":"InteractionCounter","interactionType":{"@type":"CommentAction"},"userInteractionCount":4}],"keywords":"svelte,vite,sveltekit","timeRequired":"PT6M"} {"@context":"https://schema.org","@type":"BreadcrumbList","itemListElement":[{"@type":"ListItem","position":1,"name":"Home","item":"https://daily.dev"},{"@type":"ListItem","position":2,"name":"Svelte Blog","item":"https://daily.dev/sources/svelte"},{"@type":"ListItem","position":3,"name":"What’s new in Svelte: September 2026"}]} {"@context":"https://schema.org","@type":"WebPage","@id":"https://daily.dev/posts/what-s-new-in-svelte-september-2026-tgfowohmb","comment":[{"@type":"Comment","text":"","datePublished":"2026-08-31T23:09:07.185Z","url":"https://daily.dev/posts/TgfOwohmB#c-9ro5UXdQA","author":{"@type":"Person","name":"Vikas Ganiga","url":"https://daily.dev/vikasganiga05","image":"https://avatars.githubusercontent.com/u/74750414?v=4"},"interactionStatistic":{"@type":"InteractionCounter","interactionType":{"@type":"LikeAction"},"userInteractionCount":3}},{"@type":"Comment","text":"Try attaching the unautomated-change report to the migration diff and requiring an acknowledgment for every item. Skipped manual steps should stay visible in the pull request even when an agent finishes the import rewrite.","datePublished":"2026-09-02T03:39:05.246Z","url":"https://daily.dev/posts/TgfOwohmB#c-n5hWpGs7D","author":{"@type":"Person","name":"Agustin Barrientos","url":"https://daily.dev/agustinbarrientos","image":"https://media.daily.dev/image/upload/s--5ayxQnqn--/f_auto/v1788281802/avatars/avatar_wQYYVe5Tbj0NJ7C7qPoa8?_a=BAMAMicg0"},"interactionStatistic":{"@type":"InteractionCounter","interactionType":{"@type":"LikeAction"},"userInteractionCount":2}},{"@type":"Comment","text":"SvelteKit 3 is bringing quite a few changes. I’m more curious to see how smooth that migration actually ends up being.","datePublished":"2026-09-01T10:03:26.500Z","url":"https://daily.dev/posts/TgfOwohmB#c-QIHIBrPdf","author":{"@type":"Person","name":"Taiwo Francis Oguntade","url":"https://daily.dev/taiwofrancis","image":"https://media.daily.dev/image/upload/s--px3_Pvo4--/f_auto/v1785515368/avatars/avatar_FStpm3ZejUD3qGlEeoOUS?_a=BAMAMicg0"},"interactionStatistic":{"@type":"InteractionCounter","interactionType":{"@type":"LikeAction"},"userInteractionCount":1}},{"@type":"Comment","text":"Remote functions in stable version, when?","datePublished":"2026-09-11T22:26:45.901Z","url":"https://daily.dev/posts/TgfOwohmB#c-iAyuVHCst","author":{"@type":"Person","name":"Igors Kolcins","url":"https://daily.dev/igosyee","image":"https://lh3.googleusercontent.com/a/ACg8ocIOzFoTMZ_AhQR8FsjioGyCsCgg6X0BG6l6GeTI51nmfQ=s96-c"}}]} {"@context":"https://schema.org","@type":"FAQPage","@id":"https://daily.dev/posts/what-s-new-in-svelte-september-2026-tgfowohmb#faq","mainEntity":[{"@type":"Question","name":"What new methods did SvelteMap get in Svelte 5.57?","acceptedAnswer":{"@type":"Answer","text":"Svelte 5.57 added getOrInsert and getOrInsertComputed methods to SvelteMap, covering the common read-or-initialize pattern where you fetch a value from a map or create and store it if missing. 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