ReferenceError: _self___NEXT_DATA___autoExport is not defined on next dev (16.1.4)

[leeeunsang-tmobi]

Link to the code that reproduces this issue

https://github.com/leeeunsang-tmobi/next-reproduction-16.1.4

To Reproduce

1. pnpm install
2. pnpm dev

Current vs. Expected behavior

Actual behavior:
next dev starts successfully, but the browser throws a runtime script error on load:

index.tsx:315 Uncaught ReferenceError: _self___NEXT_DATA___autoExport is not defined
    at AppContainer (index.tsx:315:27)
    at Object.react_stack_bottom_frame (react-dom-client.development.js:25904:20)
    at renderWithHooks (react-dom-client.development.js:7662:22)
    at updateFunctionComponent (react-dom-client.development.js:10166:19)
    at beginWork (react-dom-client.development.js:11778:18)
    at runWithFiberInDEV (react-dom-client.development.js:871:30)
    at performUnitOfWork (react-dom-client.development.js:17641:22)
    at workLoopSync (react-dom-client.development.js:17469:41)
    at renderRootSync (react-dom-client.development.js:17450:11)
    at performWorkOnRoot (react-dom-client.development.js:16583:35)
    at performWorkOnRootViaSchedulerTask (react-dom-client.development.js:18957:7)
    at MessagePort.performWorkUntilDeadline (scheduler.development.js:45:48)

Expected behavior:
next dev starts successfully and the page loads without browser‑side runtime errors.

Provide environment information

Operating System:
  Platform: darwin
  Arch: arm64
  Version: Darwin Kernel Version 25.0.0: Wed Sep 17 21:41:50 PDT 2025; root:xnu-12377.1.9~141/RELEASE_ARM64_T6030
  Available memory (MB): 36864
  Available CPU cores: 12
Binaries:
  Node: 24.13.0
  npm: 11.6.2
  Yarn: 1.22.22
  pnpm: 10.28.1
Relevant Packages:
  next: 16.1.4 // Latest available version is detected (16.1.4).
  eslint-config-next: N/A
  react: 19.2.3
  react-dom: 19.2.3
  typescript: 5.9.3
Next.js Config:
  output: N/A

Which area(s) are affected? (Select all that apply)

Pages Router

Which stage(s) are affected? (Select all that apply)

next dev (local)

Additional context

Regression:

• Works on 16.1.1
• Also works on 16.1.4 if I remove package.json#browserslist or override @next/swc-darwin-arm64@16.1.1.

Browserslist config:

  "browserslist": {
    "development": ["last 2 versions"],
    "production": ["chrome 72"]
  }

Diff notes
The var _self___NEXT_DATA___autoExport declaration moved out of AppContainer and into a nested Component function in 16.1.4 but the AppContainer still uses the variable.
This change causes the browser‑side error index.tsx:315 Uncaught ReferenceError: _self___NEXT_DATA___autoExport is not defined.

working

  function AppContainer(param) {
    var children = param.children;
    _s();
    var adaptedForAppRouter = _react.default.useMemo(...);
    var _self___NEXT_DATA___autoExport;
    return /*#__PURE__*/ (0,_jsxruntime.jsx)(_adapters.PathnameContextProviderAdapter, {
      router: router,
      isAutoExport: (_self___NEXT_DATA___autoExport = self.__NEXT_DATA__.autoExport) !== null && _self___NEXT_DATA___autoExport !== void 0 ? _self___NEXT_DATA___autoExport : false,
      ...
    });
  }

broken

  function AppContainer(param) {
    var children = param.children;
    _s();
    var adaptedForAppRouter = _react.default.useMemo(...);
    return /*#__PURE__*/ (0,_jsxruntime.jsx)(_adapters.PathnameContextProviderAdapter, {
      router: router,
      isAutoExport: (_self___NEXT_DATA___autoExport = self.__NEXT_DATA__.autoExport) !== null && _self___NEXT_DATA___autoExport !== void 0 ? _self___NEXT_DATA___autoExport : false,
      ...
    });
  }

  // The declaration is moved down into a nested Component function:
  Component: function() {
    var _self___NEXT_DATA___autoExport;
    return null;
  }

Workarounds:

• Remove package.json#browserslist, or
• Override @next/swc-darwin-arm64@16.1.1 (downgrade swc).

[osvaldovega]

I'm unsure if the issue is specific to the pages router, but after upgrading Next.js to version 16.1.4, our application started displaying various errors related to seemingly random issues.

I've tested the application with both Turbo and Webpack, and both encountered the same problems.

For instance, issues like a component prop not being defined with a value, when it actually was, and complaints about zod when using one of its validations, have arisen.

## Error Type
Runtime ReferenceError

## Error Message
_settings_direction is not defined

at SettingsButton (src/components/Settings/SettingsButton.tsx:90:22)

## Code Frame
  88 |         open={openDrawer}
  89 |         values={{
> 90 |           direction: settings.direction ?? config.site.direction,
     |                      ^
  91 |           layout: settings.layout ?? 'vertical',
  92 |           navColor: settings.navColor ?? 'evident',
  93 |           primaryColor: settings.primaryColor ?? config.site.primaryColor,

Next.js version: 16.1.4 (Turbopack)

Or

## Error Type
Runtime ReferenceError

## Error Message
_check is not defined

at module evaluation (src/utils/validations.ts:12:15)

## Code Frame
  10 |   {
  11 |     type: FilterFieldName.payer_email,
> 12 |     schema: z.email('invalid email address'),
     |               ^
  13 |     quickCheck: (val: string) => val.includes('@'),
  14 |   },
  15 |   {

Next.js version: 16.1.4 (Turbopack)

All these issues started happening after we migrated to the latest version. I tried to downgrade the version, and everything started working again on version 16.1.1.

Just as a note, when we upgraded Next to the latest version, v16.1.4, we also migrated all other dependencies to ensure everything was clear and up-to-date, and not just Next.js.

    "next": "16.1.4",
    "next-i18next": "^15.4.3",
    "react": "19.2.3",
    "react-dom": "19.2.3",
    "react-hook-form": "^7.71.1",
    "react-i18next": "^16.5.3",

If you need more information, just let me know.

[krishaamer]

Same here, I got a flash of content and then the page disappeared. Had to downgrade nextjs to previous version and it worked agian.