route: ssr: false, works in prod build. but in dev Error : Uncaught (in promise) SyntaxError: The requested module '/node_modules/.pnpm/react-dom@19.2.6_react@19.2.6

[hendripermana]

hey! weird one with vp dev + TanStack Start.
route: ssr: false, works in prod build. but in dev, browser module graph pulls in react-dom/server.browser.js from
somewhere deep and throws does not provide an export named 'default'. tried a custom Vite plugin to shim react-dom/server
→ no luck.
vibecoder disclaimer: i don't actually code lol, i've got an AI agent (acting as a engineer) doing the actual
work while i just vibe and point. so forgive me if i'm missing something basic — the agent's been digging for hours and
we're both stuck.
is there something about how Vite+ handles the dev SSR module graph that could cause this? any config flag i should
try? or should i just file this on the TanStack side?

Error :
Uncaught (in promise) SyntaxError: The requested module '/node_modules/.pnpm/react-dom@19.2.6_react@19.2.6/node_modules/react-dom/server.browser.js?v=cfd7a65e' does not provide an export named 'default' (at renderRouterToString.js?v=cfd7a65e:1:8)

[fengmk2]

Can you provide a code repository that can reproduce the issue?

[hendripermana]

Hi @fengmk2, thanks for looking into this!

Reproduction repo: hendripermana/permoney (branch feat/m1-5-stability-gate)

How to reproduce:

1. vp install
2. vp dev
3. Navigate to /transactions while unauthenticated (no session cookie)
4. Observe the console error:

   Uncaught (in promise) SyntaxError: The requested module
   react-dom/server.browser.js does not provide an export named "default"
   (at renderRouterToString.js:1:8)
   

Root cause (traced):

After extensive debugging, we have confirmed this is not a Vite+ issue — it is upstream in TanStack Router/Start. The import chain:

1. Route has ssr: false + a loader that calls a createServerFn protected by auth middleware
2. Auth middleware throws → TanStack Router error boundary path kicks in
3. Error boundary rendering pulls in renderRouterToString.js in the client environment
4. renderRouterToString.js does import ReactDOMServer from "react-dom/server"
5. In dev, Vite resolves this to react-dom/server.browser.js (ESM, no default export) → SyntaxError

Why Vite+ is not at fault: Production builds (vp build + vp preview) work perfectly — Rolldown tree-shakes the unused renderRouterToString import. The issue is that TanStack Router client-side error boundary code path should never import react-dom/server for ssr: false routes.

Upstream issue filed: TanStack/router#7412

Our app-level workaround: We added a beforeLoad auth guard that redirects to /login before the loader runs, preventing the error path from ever triggering. The error no longer appears in normal usage, but the underlying TanStack import graph issue remains.

Apologies for the initial vague report — my AI agent and I have since done a proper root-cause trace. This can likely be closed on the Vite+ side since the fix belongs in TanStack Router. Thanks for your time! 🙏