Hey,

It’s Michał with the August and early September edition of our monthly newsletter. This one is special, as it also covers the React Universe Conf that Callstack organizes. There were a bunch of announcements and very insightful talks and sessions, and we want to give you a glimpse of what happened, and how to watch it online. Let’s begin!

React Universe Conf highlights

There was so much amazing content from our speakers, panelists, and guests at React Universe Conf that we couldn’t help but pick some of our favorite moments (in random order) to give you a glimpse of the experience.

• LegendList v2 announcement: Jay “Legend” Meistrich released a new version of LegendList that introduces major performance and DX improvements, making list rendering more efficient for longer lists. There are still debates about which one is faster, LegendList or FlashList, and we’re excited about this “fight.”
• Uniwind waitlist announcement: Jacek Pudysz, known from hits like Unistyles, announced a new library on stage: Uniwind. It’s a drop-in replacement for NativeWind with a strong focus on performance. The waitlist is open, but the library itself is not yet available. Of course, we’ve signed in.
• React Native 1.0 on the horizon: Jorge from the React Native team teased that 1.0 is approaching, but it’s not there yet. React Native is currently focusing on the stability of releases and the maturity of the API.
• Lynx for Web beta: Lynx brought a whole team delivering a fascinating tale of how they use React on two threads (main and background) and how they work together for features such as Instant Frist-Frame Rendering or Main Thread Component. On top of that, they launched the beta of Lynx on the Web.
• Ottrelite announcement: Artur and Dominik revealed Ottrelite, a missing observability library designed to auto-instrument your app and fully compatible with OpenTelemetry. This library works across Swift, Kotlin, and C++, allowing you to hook into popular telemetry backends such as Tracy, Atrace, or Xcode instruments, all with the same interface.
• 10-year anniversary panel moments: A special panel celebrated 10 years of React, featuring stories, reflections, and insights from the community and core team. I especially enjoyed stories from before React Native was born and its early days from Tom and Christoph, who worked at Facebook back then.
• Worklets with bundle mode: Tomasz Żelawski showed us how react-native-worklets (extracted from Reanimated) can gain superpowers with a new functionality that allows it to bundle all the necessary code for the worklet.
• Modern React patterns live coded: A live coding session by Aurora demonstrated the latest React 19 patterns in action, highlighting real-world techniques developers can adopt today.
• Building Scalable Applications: A set of best practices on mobile, web, and fullstack development from Christoph Nakazawa and his 15 years of professional experience distilled into a few handy templates for holistic app development.

You can watch all the talks on the dedicated YouTube playlist or just binge-watch all of the Day 1 and Day 2 live streams. Let us know which ones were your favorite!

Community highlights

• FlashList v2: FlashList v2 is a full rewrite that no longer requires item size estimates. It’s a result of Shopify’s migration to New Architecture. Using React Native’s New Architecture for synchronous layout measurements, it ensures pixel-perfect scrolling, adaptive rendering, automatic scroll position maintenance, and built-in masonry layout. Without native code.
• React Native 0.81 is now stable: This version comes with support for Android 16, which mandates edge-to-edge displays. A key experimental addition is precompiled iOS builds, offering much faster compile times, which is available in Expo SDK 54 and Rock 0.11 by default. This release also deprecates the built-in <SafeAreaView> and moves JSC runtime support to a community-managed package, which Callstack maintains together with Expo.
• Using patch-project: An experimental tool from the Expo family that preserves custom changes made to the android and ios folders. The goal of the project is to make migrations to Expo easier by generating CNG-compatible code from your native project edits. Very neat!
• React Strict DOM vs React Native for Web in 2025: Nicolas Gallagher, the creator of React Native for Web, recommends building new universal apps with React Strict DOM, or gradually adopting it if you already use React Native for Web. If you’re fine with StyleX as a CSS and styling solution, it may be a good time to give it a go.
• Introducing Expo Launch: a new way to get to the app store: Expo has released a beta feature that lets you deploy iOS apps to TestFlight straight from the web. No config or certificates required, but it will ask you to provide your Apple credentials. It already supports web deploys, with Android support on the way.
• Introducing the React Native Nightly testing program: Maintainers of widely used native libraries can opt into automated tests to verify compatibility with upcoming React Native versions. The initiative aims to boost ecosystem stability, catch breaking changes early, and support the path toward 1.0.

Callstack Incubator highlights

React Native AI

Mike and Szymon were busy making React Native ready for iOS 26 so that you can use the full power of on-device Apple Intelligence in your React Native app from day one. This time, focusing on speech-to-text, which works surprisingly well compared to SOTA Whisper. And did I mention it’s fully compatible with Vercel’s AI SDK, now listed as one of the official community providers? There, I said it.

This work was heavily dependent on ArrayBuffers (this is how audio, but also video, is represented natively), which don’t have proper support in the TurboModule interface. As a workaround, we had to implement this functionality directly through JSI, writing a bunch of C++. This begged a question: Is it an inherent limitation of TurboModules, or wasn’t it implemented by Meta? It turned out it’s the latter, so Kamil from our team went on a quest to implement ArrayBuffers for TurboModules, which we’ll soon contribute to the core React Native for everyone to benefit.

React Native Sandbox

Aliaksandr released the React Native Sandbox library last month, and this time, he followed up with a missing and quite important functionality: bi-directional communication between isolated sandbox instances through the postMessage API. Combined with the rest of the library, and Module Federation enabled by Re.Pack, this opens the door for secure dynamic microfrontends, or mini apps that you can run safely in your app without fear of messing up with the host super app.

License Kit

Most teams think about dependencies in terms of "does it build" or "is it secure", but licenses are just as critical. Transitive dependencies can quietly introduce obligations you never agreed to.The license-kit package and CLI, together with a neat visualizer by Artur, make them visible, and once you can see them, you can act appropriately.

Rock (previously known as RNEF)

Apart from preparing the keynote for React Universe Conf, I was busy renaming the React Native Enterprise Framework into something more solid and playful: Rock.

Let’s face it: the RNEF name was never something I considered final; rather, it was a temporary patch on what the project is. And after ~6 months of throwing names I found fun at the team, transferring ownership of npm packages, and a few major releases later, we’re finally done with the rebrand.

You can now use the new npm create rock command to:

• start a new project from scratch
• migrate existing RNEF project
• migrate existing Community CLI project

Continuing our experiments with TV platforms, we've also managed to run React Native macOS with Rock. We expect to add proper support for all of these later this year.

Rozenite

Szymon is not slowing down with Rozenite, shipping plugins for MMKV, Performance API, and Network activity. It becomes a serious successor to Flipper at this point. You can quickly install it using the npx rozenite init command and enjoy a variety of ready-to-use plugins, and the possibility to write your own. We heard the Dream11 engineering team has four custom plugins for their own app already!

And this tweet shows you how quickly you (or rather Szymon) can build something on top of Rozenite that can help you iterate quickly on your project:

React Native Bottom Tabs

Oskar has been busy with an exciting client project lately, but he still manages to keep his libraries up to date. The latest release of React Native Bottom Tabs not only powers our React Universe app but also fixes a few bugs we found while developing it and supports new functionalities that are coming with iOS 26.

Re.Pack

Jakub crammed quite a lot of important updates to Re.Pack in minor release (no breaking changes!). This one comes with a smarter transformer that can distinguish when to use Babel and when it’s ok to go with SWC to make JS transforms go brrrr.

Combined, it results in over 2x faster transpilation for complex codebases such as Expensify utilizing heavy Babel plugins like React Compiler. Other than perf, Re.Pack 5.2 comes with support for the latest React Native versions, Rozenite integration, and a new progress reporter. Give it a try!

Blog

If you prefer to jump straight to the blog post versions of our releases, there you go:

• Re.Pack 5.2: Faster Babel Transforms, RN 0.80 & 0.81, Rozenite by Jakub Romańczyk: Re.Pack 5.2 is out! This release focuses on parallel, smarter transforms with a new Babel & SWC loader, official support for React Native 0.80 and 0.81, fully typed configs, support for Rozenite and more.‍
• On-Device Text To Speech on Apple Devices with AI SDK by Mike Grabowski: We’ve added on-device speech synthesis to our Apple provider for the AI SDK, completing the feature set alongside generation, embeddings, and transcription. This integration with AVSpeechSynthesizer brings fast, private, and offline text-to-speech to React Native, with support for multiple voices, languages, and even Personal Voice on iOS 17+.‍
• Secure Communication Between Isolated React Native Instances by Aliaksandr Babrykovich: The latest release of react-native-sandbox adds support for direct, secure communication between sandboxed React Native instances. Instead of routing messages through the host app, sandboxes can now talk to each other directly using a model familiar from the web: the postMessage API with origin-based access control.
• ‍React Native Enterprise Framework is Now Rock by yours truly: Meet Rock: the evolution of the React Native Enterprise Framework. Built by Callstack, Rock gives teams a stable, high-performance foundation for enterprise React Native development. From powerful build caching that cuts CI times by up to 96%, to ad-hoc iOS installs and an ecosystem of upcoming tools like Rozenite and Ottrelite, Rock is designed to help enterprises scale React Native with speed, reliability, and confidence.
• ‍Visualizing Open Source Licenses to Analyze Compliance and Reduce Legal Risk by Artur Morys-Magiera: Tracking open-source licenses isn’t just about reading package.json. Hidden obligations often live deep in transitive dependencies. license-kit visualize offers a clear, interactive map of your project’s dependency graph, complete with license details, statistics, and AI-generated summaries. Whether you’re avoiding restrictive terms or understanding how packages enter your stack, this tool gives you the visibility you need to manage licenses with confidence.‍
• On-Device Speech Transcription in React Native with Apple SpeechAnalyzer by Mike Grabowski: This post introduces speech transcription support in React Native AI, implemented using Apple’s SpeechAnalyzer and SpeechTranscriber APIs available in iOS 26. It explains how to use the AI SDK’s transcribe function to pass audio buffers, how modular analysis is configured through the SpeechAnalyzer class, and how system-level asset management ensures models are handled outside the app bundle.

Podcast and videos

• React Universe On Air Observability and OpenTelemetry in React Native: Learn how Embrace and OpenTelemetry can help React Native teams standardize observability and improve app monitoring across platforms.
• Incremental React Native Adoption in iOS Apps by Burak Güner: Brownfield development allows teams to adopt React Native gradually, embedding it into production apps one screen at a time. In this walkthrough, Burak shows how to spin up a Rock project configured for iOS, export React Native modules as XCFrameworks, import and initialize React Native in a SwiftUI app, and replace a native view with a React Native screen. By the end, you’ll understand how to extend an existing iOS app with React Native in a controlled, incremental way.
• Incremental React Native Adoption in Android Apps by Hur Ali: Are you maintaining a native Android app but want to bring React Native into the mix, without rewriting from scratch? In this video, Hur shows how to use Rock to scaffold a React Native project, package it as an AAR, and integrate it into an existing Android app. The example app is a Pokémon collection app, where we replace native UI components with a React Native fragment.

Webinars and live streams

• Live Dev Session: Routers, React Native AI, and Expo Launch recording and summary thread
• Live Dev Session: Expo SDK 54 Beta Is Here, Next.js 15.5, RNEF Renamed Rock recording and summary thread
• Live Dev Session: React Native 0.81 Is Here! Faster Builds, API Changes, and What You Need to Know recording and summary thread
• Live Dev Session: FlashList v2, Vercel AI SDK, React Compiler recording and summary thread
• How to Gradually Migrate From React Native Community CLI to Expo webinar: Learn how to migrate your React Native Community CLI app to Expo incrementally, with minimal risk. A recording of a webinar hosted by Callstack & Expo, featuring Mike Grabowski and Keith Kurak.

Upcoming events

GOSIM Hangzhou 2025

React Native is entering a new era, and so is build tooling. On Sept 13, Oskar Kwaśniewski and I will take the stage in Hangzhou to show how Rock helps large teams skip full native builds and evolve complex codebases with confidence. Meet us in Venue 9-B05, Hangzhou, China.

The Spark (React Prague Meetup)

Szymon Chmal joins the Prague React community on Sept 16 to explore the internals of React Native DevTools and how to build your own extensible plugins, no forks required. RSVP here.

React Conf 2025

React Conf is just a month away! We’re excited to be co-hosting the event again this year, together with the amazing React community. A new batch of speakers and the full agenda will be revealed very soon. Come say hi to the Callstack team or stop by our booth to chat anything React.

Let us know if you’re attending, always happy to meet you in person!

Michał