This week in react #250 : Activity, React Router, CSS-in-J | Expo, iOS blur, AI, Lynx, Squircle, | TC39, pnpm, Bun

#react #reactnative

Hi everyone!

As promised, this week is quite exciting, with a very powerful React core <Activity> component now in canary, close to becoming stable. We also have a massive Expo SDK 54 release!

npm supply chain attacks continue, this time with a Shai-Hulud worm that infects open-source maintainers and automatically publishes compromised packages. Great timing for pnpm 10.16 to come up with a new mitigation option.

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⚛️ React

React Core PR - Release <Activity> in Canary

This exciting new <Activity> component can hide a React subtree while preserving its state, and keep rendering it with lower priority. It unlocks new pre-rendering patterns along the way, and could speed up link clicks, tab clicks, back/forward navigation, stack navigation, and more. Read the reference documentation, including many use cases with interactive examples..

The long-awaited React component is approaching prime time, has been battle-tested in production by Meta, and is becoming available in React's canary workflow for the community to try out and provide feedback. You may see it appear soon in frameworks that follow the React Canary Workflow, such as Next.js App Router (coming in 15.6), which already leverages it internally in an experimental back/forward cache feature.

💸 The Road to Next - Master Full-Stack Web Development with Next.js 15 and React 19
👀 Can I use React Server Components today?: Cool resource that tests major frameworks against 12 scenarios to report which RSC-related features are supported. Next.js, Vite, and Waku all have 100% support, while others are close but do not support inline server functions/actions.
🐦 We can't use React hooks conditionally, can we?: You may discover that it’s possible to call hooks conditionally if the condition remains stable over time, and that useContext() has always allowed conditional calls despite what ESLint says (but you’d rather use use() instead). There’s also a React Nook project that lets you call hooks conditionally.
🌶 Cloudflare had a major outage due to an useEffect infinite loop triggering API requests: Yep, bad things can happen with this damn dependency array 😅.
🗓 React Paris 2026 - 🇫🇷 Paris - 26 & 27 March. First speaker lineup just dropped! Tanner Linsley, Kitze, Una, Gabriel Pichot and Elise Patrikainen are part of the lineup, and CFP just opened today!
📜 Styled-Components maintenance mode: A 40% faster fork: Styled-Components is in maintenance mode, and the folks at Sanity forked it to make it much faster thanks to React 18's useInsertionEffect hook (among other things). Both Sanity and Linear are using the fork as a temporary solution until they fully migrate to a better one.
📜 Either Tailwind is CSS-in-JS or StyleX isn’t: 100% agree on this, zero-runtime CSS-in-JS libraries like StyleX and Linaria are very similar to Tailwind CSS, it’s just the API and tooling that differ, but the outcome is the same.
📜 React Won by Default – And It's Killing Frontend Innovation: A fair criticism of the React-by-default mindset. I agree that more framework diversity could help drive innovation, but I still believe in the technical advantages React has over competitors, for example, that new <Activity> component 😇. Let’s not forget that React works on every native platform. This framing doesn’t please everyone, but to me, React doesn’t need to be the best web framework to win; it simply has to be good enough everywhere (and yet it’s still pretty damn good everywhere).
📜 What tests to write for React: A quick overview of unit, integration, and end-to-end tests in React.
📜 Quick SEO Guidelines for Your Next.js App: A quick overview of metadata, structured data, sitemap, robots, and optimizations.
💸 CodeRabbit CLI - An AI code review tool that runs directly in your terminal, seamlessly integrating with Claude, Cursor, and other coding agents
📦 React Router 7.9 - Stable middleware and type-safe context APIs, client-side error reporting: It’s also great to see progress on RSC support, almost ready for the framework mode.
📦 React Query 5.89 - Add context parameter to mutation callbacks: This lets you conveniently access the Query Client in callbacks with context.client.
📦 React-Admin 5.9 to 5.11 - Render props, headless core, shadcn-admin-kit, and more
📦 React Hook Form Persist - Automatically save and restore form data to localStorage
📦 Streamdown 1.3 - React Markdown for AI streaming - Improve perf, controls props, Mermaid config
🎥 Alem Tuzlak - React Router Middleware Is Finally Here! Here's how to migrate!
🎥 Web Dev Simplified - How To Handle Data Access Like a Senior Dev
🎥 ByteGrad - Dockerize Next.js App & Deploy To VPS In 2025

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📱 React-Native

Expo SDK 54

The new Expo SDK is finally stable and will be the last SDK to support the Legacy Architecture. It is a massive release with too many things to highlight, including:

React Native 0.81, with Android 16 support, edge-to-edge default
React 19.1, with improved stack traces based on React Owner Stacks
Precompiled iOS for faster builds
Expo UI to seamlessly integrate SwiftUI primitives with 1-1 mapping, and Jetpack Compose support is coming later
Expo Router v6 with iOS/Android native tabs (material tabs and Liquid Glass support), iOS link previews/menus, server middleware, web modals, and more
iOS 26 Liquid Glass icons and views
Expo Updates and EAS improvements
Package managers and Autolinking improvements
Apple and Android TV improvements, experimental dev client support
Major Expo File System improvements, new App Integrity API, and so much more!