Describe the bug

For SSR builds with ssr.target: 'webworker', Vite still defaults build.rolldownOptions.platform to 'node' for every server build. This causes Rolldown to emit createRequire(import.meta.url) for CJS interop, which crashes on Cloudflare Workers / workerd because import.meta.url is undefined in bundled worker modules.

The worker fails during module initialization before any request is handled:

TypeError: The argument 'path' must be a file URL object, a file URL string,
or an absolute path string. Received 'undefined'
  at createRequire (node:module:34:15)
  at null.<anonymous> (jsx-runtime.mjs:34:33)

Vite already treats ssr.target === 'webworker' as a special case elsewhere — ssr.resolve.conditions defaults to webworker/browser-style conditions, resolveEnvironmentOptions() threads isSsrTargetWebworkerEnvironment into resolve + keepProcessEnv, and resolveRolldownOptions() special-cases SSR webworker output defaults. But resolveBuildEnvironmentOptions() still hard-defaults all server builds to platform: 'node'.

We intend to submit a PR for this — see #21963 (currently draft).

Reproduction

This does not require Nitro / TanStack / a framework. A plain Vite SSR repro:

vite.config.js

import { defineConfig, defaultClientConditions } from 'vite'

export default defineConfig({
  build: { minify: false },
  ssr: {
    target: 'webworker',
    noExternal: true,
    external: ['node:assert'],
    resolve: {
      conditions: [...defaultClientConditions, 'worker'],
    },
  },
})

dep-cjs-node-assert/package.json

{ "name": "dep-cjs-node-assert", "private": true, "main": "index.cjs" }

dep-cjs-node-assert/index.cjs

const { ok } = require('node:assert')
ok(true)
module.exports = 'cjs-ok'

src/entry-worker.js

import msg from 'dep-cjs-node-assert'
addEventListener('fetch', (event) => {
  event.respondWith(new Response(msg))
})

Steps to reproduce

1. Set up the files above (or use the existing playground/ssr-webworker with a CJS fixture added)
2. Run vite build
3. Inspect the output: grep "createRequire" dist/entry-worker.js — it contains createRequire(import.meta.url)
4. Run under a worker runtime: npx wrangler dev dist/entry-worker.js — crashes at startup

System Info

System:
  OS: macOS 15.5 (Darwin 24.6.0)
  CPU: Apple M3 Max
  Memory: 36 GB
Binaries:
  Node: 22.14.0
  pnpm: 10.32.1
  bun: 1.3.2
npmPackages:
  vite: npm:rolldown-vite@^7.3.1 => 7.3.1
  rolldown: 1.0.0-rc.10

Used Package Manager

pnpm

Logs

# Build output contains createRequire:
$ grep "createRequire" .output/server/_chunks/jsx-runtime.mjs
import { createRequire } from "node:module";
var __require = /* @__PURE__ */ createRequire(import.meta.url);

# Worker crashes at startup:
$ wrangler dev .output/server/index.mjs
TypeError: The argument 'path' must be a file URL object, a file URL string,
or an absolute path string. Received 'undefined'
  at createRequire (node:module:34:15)
  at null.<anonymous> (jsx-runtime.mjs:34:33)

Validations

• Follow our Code of Conduct
• Read the Contributing Guidelines
• Read the docs
• Check that there isn't already an issue that reports the same bug to avoid creating a duplicate. Related but distinct: vite 7.1.11 causing issues CJS node builtin imports #20983 (fixed Rollup CJS plugin, does not apply to rolldown-vite per this comment), [Bug]: Could not resolve 'node:module' in rolldown:runtime (in GitHub Actions) rolldown/rolldown#8097 (fixed tsconfig load errors, not createRequire)
• Make sure this is a Vite issue and not a framework-specific issue
• Check that this is a concrete bug
• The provided reproduction is a minimal reproducible example of the bug