Svelte

The Release Candidate for SvelteKit 3 is out, signaling that no further breaking changes are planned before stable.

Remote forms got a submitted state. Remote forms now expose a submitted property, letting components react to form submission without manual tracking. The defineEnvVars API found its permanent home in this wave as well.

The QUERY HTTP method is now supported. SvelteKit 3 previews added native handling for the QUERY HTTP method in +server.js route files, aligning with RFC 9110. The source filename is also now passed to the preload filter for fonts, making per-file font loading decisions possible.

Split serverless deployments got routing fixes. A new applyReroute helper lands in Kit for adapters that manage split serverless function deployments. The Vercel and Netlify adapters both shipped fixes to correctly apply reroute results in this configuration, and the Vercel adapter separately resolved a symlink conflict during tracing.

Streamed responses are cheaper to parse. Large streamed frames are now parsed in linear time, replacing a previously quadratic path. Streamed response bodies are also built from async generators in the server runtime.

Error pages work without boilerplate. Language tools now inject page and error types into +error.svelte automatically — no manual type annotation required.

CSS handling tightened in the compiler. The 5.56.10 patch corrects escape sequence preservation in selectors, fixes :nth-child(2n of.foo) parsing where of has no trailing space, and restores CSS custom property application when the property value is falsy.