React 19 Custom Styles Not Working: "usingClientEntryPoint", Oe is undefined

[nacho-villanueva]

Describe the bug
In a previous version of react we had a custom style which updated the font size which worked. When passing to React 19 with Nextjs 15 this component stopped working. The following error is thrown:

Uncaught TypeError: can't access property "usingClientEntryPoint", Oe is undefined
    React 3
    toDOM webpack-internal:///(app-pages-browser)/./node_modules/@tiptap/core/dist/index.js:647
    create webpack-internal:///(app-pages-browser)/./node_modules/prosemirror-view/dist/index.js:1218
    syncToMarks webpack-internal:///(app-pages-browser)/./node_modules/prosemirror-view/dist/index.js:1812
    updateChildren webpack-internal:///(app-pages-browser)/./node_modules/prosemirror-view/dist/index.js:1375
    iterDeco webpack-internal:///(app-pages-browser)/./node_modules/prosemirror-view/dist/index.js:2047
  
...

    method webpack-internal:///(app-pages-browser)/./node_modules/@tiptap/core/dist/index.js:168
    addStyles webpack-internal:///(app-pages-browser)/./node_modules/@blocknote/core/dist/blocknote.js:11803
    handleSizeSelect webpack-internal:///(app-pages-browser)/./src/app/(authenticated)/(platform)/investor-updates/(editor)/drafts/[id]/edit/_components/update-text-editor/size-format-button.tsx:56
    onClick webpack-internal:///(app-pages-browser)/./src/app/(authenticated)/(platform)/investor-updates/(editor)/drafts/[id]/edit/_components/update-text-editor/size-format-button.tsx:82
    createEventHandler webpack-internal:///(app-pages-browser)/./node_modules/@mantine/core/esm/core/utils/create-event-handler/create-event-handler.mjs:7

...

blocknote-react.js:2645

To Reproduce
https://stackblitz.com/edit/github-jfdwrhzs?file=App.tsx

Changing versions of react seems to break the example above.

[amosbastian]

I have the same issue, did you manage to fix it? I guess the only solution is downgrading React?