adapter-cloudflare on Vite 8 (Rolldown): worker fails to start with createRequire(import.meta.url) when a CJS dep uses a Node builtin

Describe the bug

A SvelteKit app using @sveltejs/adapter-cloudflare on Vite 8 (which bundles Rolldown) crashes at Cloudflare Workers (workerd) startup:

Uncaught TypeError: The argument 'path' ... must be a file URL ... Received 'undefined'
  at createRequire (node:module)
[code: 10021] The Workers runtime failed to start.

It reproduces with wrangler deploy and wrangler dev --local. vite dev (Node SSR) and vite build pass — it only fails in real workerd.

Cause: Rolldown emits var __require = createRequire(import.meta.url) eagerly in a shared chunk for CJS interop, and import.meta.url is undefined in workerd. It is triggered by any CommonJS dependency in the SSR graph that uses a Node builtin (e.g. node-forge doing require("crypto")). The shared helper chunk is statically imported by output/server/index.js → the worker entry, so it is on the eager startup path even when the dependency is only used by one route. The old Astro adapter (@astrojs/cloudflare, on Vite 7 / Rollup) statically converts the same require() to an ESM import and does not hit this.

Why this is a SvelteKit-side issue (not just a Vite one): the underlying bundling behaviour is already filed at Vite — vitejs/vite#22618 and PR vitejs/vite#22619 (which restores conversion of bundled CJS builtin require() for ssr.target: 'webworker'). But Vite only applies that path when ssr.target: 'webworker' is set, and @sveltejs/adapter-cloudflare does not set it, so SvelteKit's Cloudflare SSR build uses platform: 'node' and emits the crashing createRequire shim. This issue tracks the adapter-cloudflare side. I'm happy to submit a PR once there's agreement on the approach (and once vitejs/vite#22619 lands).

Reproduction

https://github.com/basuke/sveltekit-adapter-cloudflare-createrequire-repro

(npm install --legacy-peer-deps — @sveltejs/vite-plugin-svelte still declares vite ^6||^7 as a peer — then npm run build && npx wrangler dev --local → code 10021 at startup. .svelte-kit/output/server/chunks/chunk.js contains var __require = createRequire(import.meta.url).)

Logs

service core:user:...: Uncaught TypeError: The argument 'path' must be a file URL object, a file URL string, or an absolute path string. Received 'undefined'
  at node:module:34:15 in createRequire
  at .svelte-kit/output/server/chunks/chunk.js
  ...
The Workers runtime failed to start. [code: 10021]

System Info

System:
  OS: macOS 26.5
  CPU: (20) arm64 Apple M1 Ultra
Binaries:
  Node: 22.21.1
  npm: 11.14.1
Browsers:
  Chrome: 148.0.7778.217
  Safari: 26.5
npmPackages:
  @sveltejs/adapter-cloudflare: ^7.2.8 => 7.2.8
  @sveltejs/kit: ^2.61.1 => 2.63.0
  @sveltejs/vite-plugin-svelte: ^6.2.1 => 6.2.4
  svelte: ^5.43.6 => 5.56.2
  vite: ^8.0.15 => 8.0.16

Severity

blocking an upgrade

Additional Information

Proposed direction (for discussion): once vitejs/vite#22619 lands, adapter-cloudflare (workerd) should build with ssr.target: 'webworker' — matching what @astrojs/cloudflare effectively does. Open questions:

1. Where should ssr.target: 'webworker' be set? The adapter object exposes no Vite/SSR config hook today; it would likely go in @sveltejs/kit's Vite plugin keyed off the active adapter, or via a new adapter config hook.
2. Overlap with #15627 (move adapter-cloudflare onto Cloudflare's official Vite plugin)? If that is the intended long-term path, it handles workerd builtins natively and may make ssr.target moot.

Alternatives tried (all insufficient on their own):

• ssr.target: 'webworker' alone — blocked by the Vite gap (#22619); a bundled CJS dep's require("crypto") becomes a throwing stub and the build fails.
• ssr.noExternal: true — builds, but crypto resolves to a browser stub missing randomBytes at runtime.

Start with the adapter-cloudflare configuration and SvelteKit’s Vite plugin, then compare the reproduction’s .svelte-kit/output/server/chunks/chunk.js and output/server/index.js with the Vite #22619 behavior. Review the adapter configuration hook questions and the relationship to #15627. Done means the Vite 8 Cloudflare build starts in workerd without the eager createRequire(import.meta.url) failure while preserving CommonJS Node builtin usage.