Cloudflare workerd SSR: React module duplication in HeadContent useContext when used with TanStack Start + @cloudflare/vite-plugin

[Konan69]

Setup

• vite-plus (alias vite → @voidzero-dev/vite-plus-core) 0.1.22
• @cloudflare/vite-plugin ^1.37.2 (workerd SSR environment)
• @tanstack/react-start ^1.168.10 + @tanstack/react-router ^1.170.7
• React 19, @vitejs/plugin-react ^6.0.2
• bun workspaces, single app uses TanStack Start

vite.config.ts mirrors the working garden setup exactly (vanilla Vite 8 + same environments.ssr.optimizeDeps.include list + same plugin order):

```ts
export default defineConfig({
resolve: { tsconfigPaths: true, dedupe: ["react", "react-dom"] },
environments: {
ssr: {
optimizeDeps: {
include: [
"react", "react/jsx-runtime", "react/jsx-dev-runtime",
"react-dom", "react-dom/server",
"@tanstack/react-router > @tanstack/react-store",
],
},
},
},
plugins: [
cloudflare({ viteEnvironment: { name: "ssr" } }),
agents(),
tailwindcss(),
tanstackStart(),
viteReact(),
],
});
```

What happens

SSR shell render of `HeadContent` crashes with React invalid-hook-call:

```
TypeError: Cannot read properties of null (reading 'useContext')
at exports.useContext (deps_ssr/react.js?v=…:706)
at useRouter (@tanstack/react-router/src/useRouter.tsx:20)
at useTags (@tanstack/react-router/src/headContentUtils.tsx:213)
at HeadContent (@tanstack/react-router/src/HeadContent.dev.tsx:22)
```

i.e. the classic two-copies-of-React-in-workerd-SSR situation that cloudflare/workers-sdk#11825 describes. Browser ends up on the JSON 500 page (`{"status":500,"message":"HTTPError"}`).

The exact same source tree + the exact same config, run on vanilla Vite 8 in another project (https://github.com/voidzero-dev/garden parallel — its `apps/web` works fine), renders cleanly.

Comparison

	vanilla Vite 8 (garden)	vite-plus-core 0.1.22 (this repo)
Same vite.config	works	500 with useContext null in HeadContent
Same plugin order	works	broken
Same SSR optimizeDeps.include	works	broken

Switching this repo's catalog alias to vanilla Vite 8 doesn't fully fix it either — first `/` render works, but on any subsequent SSR render of the route (HMR reload, client navigate, etc.) the same useContext null surfaces.

Suspicion

@voidzero-dev/vite-plus-core ships its own (rolldown-backed?) Vite that handles `environments.ssr.optimizeDeps` differently from upstream Vite's dep optimizer, so the React module the workerd runner ends up with isn't the same instance the route bundle imports. This trips every provider hook downstream (useContext in HeadContent, useEffect in QueryClientProvider, etc.).

Repro repo: I can put one up if helpful — but the diff against the existing TanStack Start cloudflare example is essentially "swap upstream Vite for the vite-plus-core alias and add @cloudflare/vite-plugin".

Related

• @cloudflare/vite-plugin: SSR causes "Invalid hook call" with React due to module duplication cloudflare/workers-sdk#11825
• Can't find module "cloudflare:workers" when using RC with the Cloudflare Vite Plugin TanStack/router#5208