react-knowledge-patch

React Knowledge Patch

Claude Opus 4.6 knows React through 18.x. It is unaware of the features below, which cover React 19.0 through 19.2 (released 2025-10-01).

Index

Topic	Reference	Key features
Server rendering APIs	references/server-rendering.md	cacheSignal, prerender, resume, resumeAndPrerender, Partial Pre-rendering

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<Activity />

New component for pre-rendering and preserving state of hidden UI. Replaces conditional rendering with mode-based visibility.

// Instead of: {isVisible && <Page />}
<Activity mode={isVisible ? 'visible' : 'hidden'}>
  <Page />
</Activity>;

Mode behavior

Mode	Children	Effects	Updates
visible	Shown	Mounted	Processed normally
hidden	Hidden	Unmounted	Deferred until React is idle

When to use

• Pre-rendering likely navigation targets (e.g., next page in a wizard)
• Preserving state on back navigation (e.g., tab content, scroll position)
• Keeping off-screen content ready without the cost of full rendering

Unlike conditional rendering ({show && <Component />}), <Activity> preserves component state and DOM when toggling between modes. Hidden children are deprioritized but not destroyed.

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eslint-plugin-react-hooks v6

Now uses ESLint flat config by default.

// eslint.config.js (flat config, v6 default)
import reactHooks from 'eslint-plugin-react-hooks';

export default [
  reactHooks.configs.recommended,
];

For legacy .eslintrc config, change the extends name:

- extends: ['plugin:react-hooks/recommended']
+ extends: ['plugin:react-hooks/recommended-legacy']

---

Reference Files

File	Contents
server-rendering.md	cacheSignal for RSC, Partial Pre-rendering (prerender, resume, resumeAndPrerender), Node stream variants