Core rules

Recipes

Default browser target is raised again under baseline-widely-available.
CommonJS default-import interop becomes more consistent and may expose packages that relied on older ambiguous behavior.
Vite stops resolving browser vs module via format sniffing and follows configured resolve.mainFields more strictly.
JS API build() now throws BundleError with nested .errors when multiple Rolldown-level errors are present.
Rolldown transition becomes more explicit: build.rollupOptions / worker.rollupOptions are deprecated in favor of *.rolldownOptions.

Rolldown moves to 1.0.3 (was 1.0.2 in 8.0.14); if you maintain plugin or build guidance, validate it against the current Rolldown behavior instead of assuming early 8.0.x patch semantics.
Dev server now sends HTTP 408 on request timeout instead of hanging the connection (8.0.15).
launch-editor-middleware rejects UNC paths and Windows alternate paths, closing a local path-traversal vector (8.0.16); relevant if you expose the dev server beyond localhost.
8.0.15 fixes: /@fs/ HTML-proxy cache-key mismatch, relative-glob-in-virtual-module errors when no files match, closing the Rolldown bundle when write() rejects, and onWarn for viteResolvePlugin in JS plugin containers.
transformIndexHtml handles trailing-slash paths more reliably, which matters for plugins and static deploy setups that rewrite or inject HTML on directory-style URLs.
Dependency scanning now passes Oxc JSX options through the optimizer path, so JSX-heavy linked dependencies should behave closer to the main transform pipeline.