svelte@5.53.6

sveltejs/sveltesvelte@5.53.6Feb 27, 2026by github-actions[bot]

AI Summary

Performance optimizations for the compiler (parser and analysis phases) are the main focus, alongside fixes for `SvelteMap` handling `undefined` values and SSR-specific event handler behavior.

Key Highlights

Optimize parser hot paths for faster compilation
Fix `SvelteMap` incorrectly handling keys with `undefined` values
Fix `SvelteURL` search setter to return normalized values
Optimize compiler analysis phase
Fix SSR case-insensitive event handlers

Full Release Notes

### Patch Changes

-   perf: optimize parser hot paths for faster compilation ([#17811](https://github.com/sveltejs/svelte/pull/17811))

-   fix: `SvelteMap` incorrectly handles keys with `undefined` values ([#17826](https://github.com/sveltejs/svelte/pull/17826))

-   fix: SvelteURL `search` setter now returns the normalized value, matching native URL behavior ([#17828](https://github.com/sveltejs/svelte/pull/17828))

-   fix: visit synthetic value node during ssr ([#17824](https://github.com/sveltejs/svelte/pull/17824))

-   fix: always case insensitive event handlers during ssr ([#17822](https://github.com/sveltejs/svelte/pull/17822))

-   chore: more efficient effect scheduling ([#17808](https://github.com/sveltejs/svelte/pull/17808))

-   perf: optimize compiler analysis phase ([#17823](https://github.com/sveltejs/svelte/pull/17823))

-   fix: skip redundant batch.apply ([#17816](https://github.com/sveltejs/svelte/pull/17816))

-   chore: null out current_batch before committing branches ([#17809](https://github.com/sveltejs/svelte/pull/17809))