Summary

React 19 is not correctly attaching event listeners for custom element events during server-side rendering hydration. This means custom event handlers, defined using React's `on<CustomEventName>` prop, are not active until after the initial client-side render, requiring a fix in React's hydration logic for custom elements.

Skills Required

Files Likely Touched

• packages/react-dom/src/client/ReactDOMHydration.js
• packages/react-dom-bindings/src/client/ReactDOMComponentTree.js
• packages/react-dom/src/events/ReactSyntheticEvent.js
• packages/react-dom/src/events/DOMEventPluginUtils.js

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