astro@6.4.7

Patch Changes

• #17035 197e50e Thanks @astrobot-houston! - Fixes getRelativeLocaleUrl, getAbsoluteLocaleUrl, and getAbsoluteLocaleUrlList to strip trailing slashes when trailingSlash: 'never' is configured

• #16967 3719765 Thanks @astrobot-houston! - Fixes double URL-encoded paths returning 400 Bad Request on on-demand routes

  Previously, any URL containing a double-encoded character (like %255B, which is [ encoded twice) was unconditionally rejected with a 400 Bad Request before middleware or route handlers could run. This broke embedded tools like Sanity Studio whose client-side router legitimately produces double-encoded URLs.

  The fix replaces the rejection approach with iterative decoding — multi-level percent-encoding is now fully resolved to its canonical form before being passed to middleware and route matching. This preserves the security fix for CVE-2025-66202 (middleware authorization bypass via double encoding) because middleware now always sees the fully decoded path, making bypass impossible. For example, /api/%2561dmin is decoded to /api/admin, which middleware can correctly block.

• #17066 2f4d92a Thanks @matthewp! - Fixes prerendered redirect targets being incorrectly bundled into the SSR function in hybrid mode, causing massive bundle size inflation

• #16882 621beb7 Thanks @jettwayio! - fix(render): honour compressHTML when joining head elements

• #16892 8d753b0 Thanks @astrobot-houston! - Fixes custom elements in MDX having their children's slot attribute stripped by the JSX runtime

  When custom elements (tags with hyphens like <my-element>) are used in MDX files, the slot HTML attribute on their children is now correctly preserved. Previously, the shared JSX runtime would treat slot as an Astro slot assignment and remove it from the output, breaking Shadow DOM named slot distribution for web components.

• #16957 544ee76 Thanks @thelazylamaGit! - Fixes stale inline CSS in server-rendered HTML after CSS file edits during dev

  When editing a CSS file (.css, .scss, etc.) during development, the inline <style> tags in server-rendered HTML would retain old CSS content instead of updating. This caused a brief flash of old CSS (FOUC) on fresh page loads before Vite's client-side HMR corrected the styles.

  The fix ensures that Astro's per-route dev CSS virtual modules are invalidated in both the SSR module graph and the module runner's evaluation cache when a style file changes, so the next page render picks up the fresh CSS.

• #17044 2220d22 Thanks @astrobot-houston! - Fixes CSS from client:only islands leaking to unrelated pages when Rollup bundles non-CSS-importing modules into the same chunk as CSS-importing modules

• #17040 7c4763d Thanks @astrobot-houston! - Fixes HMR not triggering for files inside the src/middleware/ directory during dev

• #16672 52fc862 Thanks @martinheidegger! - Fixes support for numeric IDs in YAML frontmatter when using content collection references

• #16762 9de80ae Thanks @alexanderdombroski! - Adds a JSON schema to the Wrangler configuration file generated when running astro add cloudflare

• #17046 ef771ec Thanks @ematipico! - Improves the diagnostics emitted when Astro parses incorrect .astro files.