Vite+ config errors on running tests after scaffolding react compiler

[SiddharthPant]

Describe the bug

I scaffolded a tanstack start app using vp create opting to use react compiler.
vp test runs and test passes but hangs with errors denoting possibly some CJS loading confusion with react lib.
To make testing work with react compiler enabled, I had to create a separate vitest.config.ts.

I know the repro app I shared, has errors and warnings due to missing vite 8 react compiler related changes in default tanstack start scaffold but even after fixing that with new rolldown babel plugin same error will occur. I just kept it as is to keep repro steps minimum. If you create any tests those will run successfully but process still hangs with same error.

On a side note the Vite+ start template is using old cli of Tanstack start they recommend a new one now.

Reproduction

https://github.com/SiddharthPant/vp-test

Steps to reproduce

vp create @tanstack/start
VITE+ - The Unified Toolchain for the Web

◇ Which package manager would you like to use?
  pnpm

◇ pnpm@10.33.0 installed

◇ Which agents are you using?
  ChatGPT (Codex), Claude Code

◇ Which editor are you using?
  VSCode

◇ Set up pre-commit hooks to run formatting, linting, and type checking with auto-fixes?
  Yes


Generating project…

Running: pnpm dlx @tanstack/create-start --no-install --no-toolchain
Warning: @tanstack/create-start is deprecated. Use "tanstack create" or "npx @tanstack/cli create" instead.
         See: https://tanstack.com/start/latest/docs/framework/react/quick-start

┌  Let's configure your TanStack Start application
│
◇  What would you like to name your project?
│  vp-test
│
◇  Select deployment adapter
│  Nitro (agnostic)
│
◇  Would you like to include demo/example pages?
│  No
...... ===========Choose Compiler here to cause the bug in testing===============......
◇  What add-ons would you like for your project?
│  Compiler
│
◇  Would you like to initialize a new git repository?
│  Yes
....
◇ Scaffolded vp-test
• Node 24.14.1  pnpm 10.33.0
✓ Dependencies installed in 15s
→ Next: cd vp-test && vp dev

System Info

`vp env current`

VITE+ - The Unified Toolchain for the Web

Environment:
  Version  24.14.1
  Source   lts

Tool Paths:
  node  /Users/sid/.vite-plus/js_runtime/node/24.14.1/bin/node
  npm   /Users/sid/.vite-plus/js_runtime/node/24.14.1/bin/npm
  npx   /Users/sid/.vite-plus/js_runtime/node/24.14.1/bin/npx


`vp --version`

VITE+ - The Unified Toolchain for the Web

vp v0.1.14

Local vite-plus:
  vite-plus  v0.1.14

Tools:
  vite             v8.0.2
  rolldown         v1.0.0-rc.11
  vitest           v4.1.1
  oxfmt            v0.42.0
  oxlint           v1.57.0
  oxlint-tsgolint  v0.17.3
  tsdown           v0.21.4

Environment:
  Package manager  pnpm v10.33.0
  Node.js          v24.14.1

Used Package Manager

pnpm

Logs

~/projects/vp-test ❯ vp test                                                                                                                                                            on  main via  v24.14.1
VITE+ - The Unified Toolchain for the Web

The plugin "vite-tsconfig-paths" is detected. Vite now supports tsconfig paths resolution natively via the resolve.tsconfigPaths option. You can remove the plugin and set resolve.tsconfigPaths: true in your Vite config instead.
 RUN  /Users/sid/projects/vp-test

No test files found, exiting with code 1

include: **/*.{test,spec}.?(c|m)[jt]s?(x)
exclude:  **/node_modules/**, **/.git/**

ReferenceError: module is not defined
    at /Users/sid/projects/vp-test/node_modules/.pnpm/react@19.2.4/node_modules/react/index.js:6:3
    at ESModulesEvaluator.runInlinedModule (file:///Users/sid/projects/vp-test/node_modules/.pnpm/@voidzero-dev+vite-plus-core@0.1.14_@types+node@22.19.15_esbuild@0.27.4_jiti@2.6.1_tsx@4.21.0_typescript@5.9.3/node_modules/@voidzero-dev/vite-plus-core/dist/vite/node/module-runner.js:988:161)
    at ModuleRunner.directRequest (file:///Users/sid/projects/vp-test/node_modules/.pnpm/@voidzero-dev+vite-plus-core@0.1.14_@types+node@22.19.15_esbuild@0.27.4_jiti@2.6.1_tsx@4.21.0_typescript@5.9.3/node_modules/@voidzero-dev/vite-plus-core/dist/vite/node/module-runner.js:1243:80)
    at ModuleRunner.cachedRequest (file:///Users/sid/projects/vp-test/node_modules/.pnpm/@voidzero-dev+vite-plus-core@0.1.14_@types+node@22.19.15_esbuild@0.27.4_jiti@2.6.1_tsx@4.21.0_typescript@5.9.3/node_modules/@voidzero-dev/vite-plus-core/dist/vite/node/module-runner.js:1150:73)
close timed out after 10000ms
Tests closed successfully but something prevents Vite server from exiting
You can try to identify the cause by enabling "hanging-process" reporter. See https://vitest.dev/guide/reporters.html#hanging-process-reporter

Validations

• Read the Contributing Guidelines.
• Check that there isn't already an issue for the same bug.
• Confirm this is a Vite+ issue and not an upstream issue (Vite, Vitest, tsdown, Rolldown, or Oxc).
• The provided reproduction is a minimal reproducible example.

[claude]

Analysis

Understanding the issue: When the React Compiler Babel plugin is active in the Vite config, React's CJS index.js ends up being evaluated by Vite's ESModulesEvaluator.runInlinedModule. Since react/index.js uses module.exports (CJS syntax), the ESM evaluator throws ReferenceError: module is not defined. The process then hangs because Vitest can't cleanly shut down after the runner error.

Why it works without React Compiler: Without the Babel plugin, React is loaded via Node's native require() (marked as external), which handles CJS correctly. The React Compiler plugin changes how modules are resolved/transformed in the Vite pipeline, causing React to be pulled into the inlined module path.

---

Relevant Code

• packages/test/build.ts (lines 2366–2441): Contains patchServerDepsInline() — a build-time patch that auto-adds packages like @testing-library/jest-dom to server.deps.inline for expect.extend() compatibility (see @testing-library/jest-dom/vitest setup fails with "Invalid Chai property: toBeInTheDocument" #897). A similar mechanism could handle the React Compiler case, but in the opposite direction: ensuring react/react-dom are in server.deps.external when React Compiler is detected.
• packages/cli/src/create/templates/remote.ts (line 121–125): The autoFixRemoteTemplateCommand function handles TanStack Start scaffolding — a good place to inject a post-scaffold config if needed.

---

Fixable? Yes

Complexity: Medium. Two possible approaches:

Option A — Runtime auto-detection patch (preferred)

Extend the vitest config patching in packages/test/build.ts to detect when the user's project has React Compiler installed and automatically add react/react-dom to server.deps.external. This mirrors the existing patchServerDepsInline pattern for #897, but targets CJS interop rather than expect.extend().

Steps:

1. In patchServerDepsInline() (or a new patchReactCompilerCompat() function), add logic that checks whether @react-compiler/runtime or babel-plugin-react-compiler is resolvable in the project.
2. If detected, push react and react-dom into testConfig.server.deps.external (not inline), so they're loaded via Node's require().
3. Add a test case to packages/test/__tests__/build-artifacts.spec.ts covering this patch.

Option B — Template-level fix

After scaffolding a TanStack Start project with React Compiler, inject a vitest.config.ts with the necessary server.deps.external config. This is simpler but less ergonomic (users who add React Compiler later won't get the fix).

---

Concerns / Blockers

1. Upstream compatibility: This could also be an upstream Vite/Vitest issue. Worth checking if plain Vitest (without vite-plus) has the same problem with React Compiler + TanStack Start. If so, the fix belongs upstream and we'd just document it.
2. Template deprecation: The issue also mentions that @tanstack/create-start is deprecated in favor of tanstack create / npx @tanstack/cli create. This should be tracked separately (the warning already shows during vp create).
3. React Compiler detection: If the user adds React Compiler via a Vite plugin that wraps it (not a direct babel-plugin-react-compiler dep), package presence detection may not be reliable. We may also need to check for @babel/plugin-transform-react-compiler or the newer babel-plugin-react-compiler.

Recommended next step: Reproduce with plain Vitest to confirm it's vite-plus-specific before implementing the patch.

[SiddharthPant]

Meanwhile, this is unrelated but I have raised a feature update here: TanStack/cli#419
in the tanstack cli repo so that they update the starter to fix Vite 8 react compiler config. They are still using Vite v7 and have not made the required rolldown changes in their starter. So when vite-plus adds its own vite v8 dependency and user is using react-compiler then starter template results in a broken config.
I said above its unrelated as error happens regardless of broken or working config.

[SiddharthPant]

I have raised another feature request in this repo to make vp create use Tanstack's new cli instead of the old one here: #1238 (comment)

The new one still has vite 7. So it doesn't change anything but simply removes that pesky warning I highlighted above.