RSC moduleMap undefined on first request: Cannot read properties of undefined (reading 'moduleMap')

[justinfinnn]

Bug

After a successful vinext deploy, the deployed Worker crashes on every request with:

TypeError: Cannot read properties of undefined (reading 'moduleMap')

HTTP response: 500 error code: 1101 (Worker threw an unhandled exception)

Environment

• vinext: 0.0.13
• React: 19.2.0
• Next.js: 15.2.x
• Deployment: Cloudflare Workers (via vinext deploy or wrangler deploy --config dist/server/wrangler.json)

Steps to reproduce

1. vinext build completes successfully
2. wrangler deploy using the generated dist/server/wrangler.json
3. Visit the deployed URL — Worker immediately returns 500/1101
4. The error is Cannot read properties of undefined (reading 'moduleMap') from the RSC layer

Root cause (suspected)

The RSC client manifest / module map is not being correctly initialized or passed between the RSC server layer and the SSR edge environment. The dist/server/ worker attempts to use the module map before it's populated.

Workaround

Use Next.js output: 'export' (static export) and deploy the out/ directory as a static asset Worker:

# wrangler.toml
name = "my-app"
compatibility_date = "2026-02-27"
workers_dev = true

[assets]
directory = "./out"

This bypasses RSC/SSR entirely and works reliably, though it sacrifices server-side rendering.

Expected behavior

The deployed Worker should serve the app successfully without RSC initialization errors.

[StringerBell69]

This appears to be a React version compatibility issue, react-server-dom-webpack requires react@^19.2.4 for RSC support, but you're on react@19.2.0. Try upgrading React with npm install react@latest react-dom@latest and redeploy.

If the issue persists after upgrading, it may be a @vitejs/plugin-rsc or @cloudflare/vite-plugin issue with module map initialization in the Workers runtime, in that case, file a bug on the relevant plugin repo.

[StringerBell69]

Your repro uses vinext build + wrangler deploy manually, which bypasses the React compatibility checks that vinext deploy performs automatically.