RadixUI & shadcn/ui not working

On 21st of October, Next.js 15 was officially released, yay! 🎉

Among the release notes there’s this note:

In version 15, the App Router uses React 19 RC

Depending on a release candidate? 🤔 How bad can it be?

Although React 19 is still in the RC phase, our extensive testing across real-world applications and our close work with the React team have given us confidence in its stability.

And that’s probably true. What wasn’t accounted for are the numerous dependencies on react: ^18.x all over the internet. Including radix-ui/icons, which makes shadcn/ui unable to install properly. And sadly, we were using those 😔

It took a good full week to fix the issue. But more libraries were affected: NextUI, zustand, heroicons, Material UI and I’m guessing many more.

All of that isn’t directly Vercel’s fault. But it kind of is, isn’t it?