Minimal repro for a regression introduced in Astro 6.3.2: Astro action calls return HTTP 500 in Vite dev mode when using the @astrojs/cloudflare adapter with prerenderEnvironment: "node" and at least one catch-all prerendered route. The same action works correctly after a production build and preview.

Observed error in the Vite terminal:

[ERROR] [vite] Internal server error: fetch failed
  at async _Miniflare.dispatchFetch (…/miniflare/src/index.ts:2807:20)
  at async file:///…/@cloudflare/vite-plugin/dist/index.mjs:34103:19

npm install
npm run dev

Open http://localhost:4321, click Call Action.

Expected: { "message": "Hello, World!" }

Actual: The network request to /_actions/hello returns HTTP 500.

The action works correctly when built and previewed:

npm run build
npm run preview

PR #16562 (included in 6.3.2) introduced a new prerender middleware in vite-plugin-astro-server/plugin.ts. It uses matchAllRoutes() to decide whether the Node.js prerender handler should intercept a request.

Because spread / catch-all routes like [...page].astro match any pathname (their pattern covers /_actions/hello, /anything, etc.), the check matches.some(route => route.prerender) is true for every action request.

The prerender handler therefore fires for actions with { prerenderOnly: true }. Inside handleRequest, devMatch('/_actions/hello') finds no matching static path in getStaticPaths (action URLs are not page routes), so it returns handled = false. The middleware then falls through to next(), which routes the request to @cloudflare/vite-plugin, which dispatches it to the local workerd/miniflare process via _Miniflare.dispatchFetch. That dispatch fails with fetch failed.

Before 6.3.2 the prerender middleware forwarded all requests to the Node.js handler unconditionally — actions were handled there and worked. The fix in #16562 changed that unconditional forwarding and unintentionally broke the action path.