useEffectEvent usage

[acd02]

Link to the code that reproduces this issue

https://stackblitz.com/edit/stackblitz-starters-tbmhnpxw?file=app%2Fcontent.tsx

To Reproduce

1. visit 👉 https://stackblitz.com/edit/stackblitz-starters-tbmhnpxw?file=app%2Fcontent.tsx
2. wait for the dev server to start—you'll see a runtime error: ⁠useEffectEvent is not a function

Current vs. Expected behavior

Current:
Runtime error: ⁠useEffectEvent is not a function

Expected:
The ⁠useEffectEvent hook from React 19.2.0 should work

Provide environment information

Operating System:
  Platform: linux
  Arch: x64
  Version: Ubuntu 20.04.0 LTS Thu Oct 02 2025 17:39:25 GMT+0200 (Central European Summer Time)
  Available memory (MB): NaN
  Available CPU cores: 2
Binaries:
  Node: 20.19.1
  npm: 10.8.2
  Yarn: 1.22.19
  pnpm: 8.15.6
Relevant Packages:
  next: 15.4.6 // There is a newer version (15.5.4) available, upgrade recommended! 
  eslint-config-next: 15.5.4
  react: 19.2.0
  react-dom: 19.2.0
  typescript: 5.8.3

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

Not sure

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

next dev (local)

Additional context

With the release of React 19.2.0, I wanted to test the new useEffectEvent hook, but importing it causes a runtime error in a Next.js app

[dantman]

Still happening in the latest Next.js when trying to SSR a page in the app directory using a "use client" component that imports useEffectEvent.

Relevant Packages:
  next: 15.5.4 // Latest available version is detected (15.5.4).
  eslint-config-next: 15.5.3
  react: 19.2.0
  react-dom: 19.2.0
  typescript: 5.9.2
Next.js Config:
  output: N/A

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[denk0403]

I believe because Next.js relies on various React canary features, they alias React imports with a pre-compiled version of React to ensure consistency across the framework. So I don't think upgrading React in your package.json really does anything, you'll have to wait until a future Next.js release which updates the pre-compiled version of React to 19.2 to use the new features.

[acd02]

Thanks for the heads up! Guess I'll have to wait for an upcoming Next.js release with React 19.2.0 🤞
Too bad though—since Next.js 15.5+ isn't supported on StackBlitz due to an error related to ⁠workUnitAsyncStorage, so I won't be able to test the new React features in a Next.js app there. But that's another matter 😅

[denk0403]

If you want to use useEffectEvent in an earlier version of React, you can pretty closely polyfill it.

[baileys-li]

<Activity /> isn't also worked now, because Next monkey patch React

[icyJoseph]

<Activity /> isn't also worked now, because Next monkey patch React

Hi! My comment won't be all that helpful to the subject matter, but it is not monkey patched. I've seen some confusion on this matter on various channels. As per, https://nextjs.org/docs#react-version-handling

App Router: Uses React canary releases built-in, which include all the stable React 19 changes, as well as newer features being validated in frameworks, prior to a new React release.

In PRs like this sample, #84416, the built-in version is bumped, passes CI, etc... all of that, eventually it makes it to a stable release.

So it is not like a new React canary release could somehow break your app using stable next@latest.

AFAIK, both Activity and useEffectEvent stable should be available in next@canary already.

The OP issue is still open. Let's see if other team members have anything more to say.

[shaked-frame]

Is this expected in the next version of nextjs? when will it be a part of a stable release?
Just wen to update today and was sad to see that I cant use the new Activity component :(

[JesseKoldewijn]

@icyJoseph just on the topic, do you know if there can be a difference in react definition (as in, difference in react channel) between server-side and client-side? As I believe this could potentially be a case of Next trying to ssr pre-hydration failure

[DipakHalkude]

This issue occurs because Next.js bundles its own pre-compiled version of React to maintain framework stability, so updating React in your package.json doesn't actually change the React version used by Next.js. You'll need to wait for an upcoming Next.js release that includes React 19.2.0+ to access new features like useEffectEvent and Activity components. In the meantime, you can use a polyfill implementation or monitor Next.js release notes for when these React updates are integrated.

[shaked-frame]

This issue occurs because Next.js bundles its own pre-compiled version of React to maintain framework stability, so updating React in your package.json doesn't actually change the React version used by Next.js. You'll need to wait for an upcoming Next.js release that includes React 19.2.0+ to access new features like useEffectEvent and Activity components. In the meantime, you can use a polyfill implementation or monitor Next.js release notes for when these React updates are integrated.

Thanks for the clarification

[cprcrack]

Same issue, Activity is undefined using next 15.5.4 and react 19.2.0. Repro: https://codesandbox.io/p/devbox/wf4czx?file=%2Fpackage.json

[cprcrack]

I temporarily fixed this with npm install next@15.6.0-canary.35, while Next.js releases the next stable version