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.
Post #2321
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What’s new in Svelte: September 2026
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