ssr.target: 'webworker' still defaults Rolldown SSR builds to platform: 'node', emitting createRequire(import.meta.url) that crashes on Workers

[jmalmo]

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)

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'.

I am happy to take a stab at a PR if the team points us in the right direction.

Reproduction

https://github.com/jmalmo/vite-ssr-webworker-createrequire-repro

Steps to reproduce

1. git clone https://github.com/jmalmo/vite-ssr-webworker-createrequire-repro && cd vite-ssr-webworker-createrequire-repro
2. pnpm install
3. pnpm run build
4. pnpm run check — shows createRequire(import.meta.url) in output
5. pnpm run preview — crashes with TypeError: The argument 'path' must be a file URL object...

System Info

System:
  OS: macOS 15.6.1 (Darwin 24.6.0)
  CPU: Apple M4 Max
  Memory: 48 GB
Binaries:
  Node: 22.13.1
  bun: 1.3.3
  pnpm: 10.32.1
npmPackages:
  vite: npm:rolldown-vite@^7.3.1 => 7.3.1
  rolldown: 1.0.0-rc.10 (transitive via rolldown-vite)

Used Package Manager

bun

Logs

Click to expand!

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

# Worker crashes at startup:
$ npx wrangler dev .output/server/index.mjs
Uncaught 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.
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• Check that this is a concrete bug. For Q&A open a GitHub Discussion or join our Discord Chat Server.
• The provided reproduction is a minimal reproducible example of the bug.

[jmalmo]

I put together a draft PR at #21963 that takes one possible approach: propagating isSsrTargetWebworkerEnvironment into resolveBuildEnvironmentOptions() to use platform: 'browser' + esmExternalRequirePlugin for webworker SSR. The existing playground/ssr-webworker tests pass with this change.

That said, switching the platform from 'node' to 'browser' is a broader change than just fixing createRequire — it affects how Rolldown handles CJS interop, __dirname/__filename shims, and Node built-in resolution across the board for worker builds. We haven't tested every edge case and there may be side effects we're not seeing.

This might not be the right approach at all - the team may prefer 'neutral' over 'browser', or a more surgical fix like only applying esmExternalRequirePlugin without changing the platform, or something else entirely. I'm happy to adjust or scrap the PR based on your guidance.

[iflamed]

Same problem on Cloudflare Pages when I use the package swr.