React Native Evals, Expo SDK 55, and WebAssembly in Hermes

Authors
Michał Pierzchala
Principal Engineer
@
Callstack

Hey,

It’s Michał with a bunch of updates from React Native community and Callstack Incubator in February and early March: new Expo SDK, State of React Native 2025 survey results, Evals for AI writing React Native, and many more.

Let’s jump right in!

Community highlights

  • Expo SDK 55: This one comes with React Native 0.83, new native features in Expo Router (Zoom transition, Stack.Toolbar API, dynamic colors), tools for AI agents (expo/skills), and 75% smaller OTA diffs thanks to Hermes bytecode diff support. The legacy expo-av module has been removed and replaced by expo-video & expo-audio.
  • WebAssembly Comes to Hermes: There is a new way to integrate C/C++, Rust, and more into your React Native app. It’s powered by native WebAssembly support in Hermes with the ability to precompile WASM to Hermes bytecode. Tzvetan is also teasing hermes-node as a CLI compatible with Node.js but running Hermes instead of V8. The team is cooking.
  • Sparkling - Unlocks Lynx at TikTok Scale: ByteDance introduced Lynx last year as a framework-agnostic alternative to React Native. Until now, there was no straightforward way to bootstrap a new Lynx app from scratch (sic!). Sparkling aims to change that by providing the tooling the Lynx ecosystem has been missing, it’s like Expo for React Native. Łukasz from our podcast team posted a longer article on his Sparkling explorations, check it out.
  • Google is expanding billing choice on Google Play: Google Play introduced alternative billing systems, effectively cutting fees to 15–20% for apps and 10% for subscriptions. What’s more, there’s a new Registered App Stores program for easier installation flow for alternative Android app stores (a.k.a sideloading) that meet certain quality and safety benchmarks.
  • State of React Native 2025: The results are in, showing New Architecture at 80% adoption rate, more usage of native navigation primitives and Expo Router, a shift towards Tailwind-style utility classes for styling instead of relying on component libraries, more React Native Skia usage, and not that many developers complaining about the direction the project is going or that building with React Native is overly complex (it got way easier lately, hasn’t it?).

Callstack Incubator highlights

React Native Evals

Ever wondered which model works best with React Native by default? Now you don't have to. Our team shipped AI evals for React Native apps. We start with 43 common scenarios right now across animations, state management, navigation, and we have many more coming in the pipeline.

Apart from overall results and top 3 models, you’ll see token usage and API cost, so you have more dimensions to compare. We’re going to re-run these evals once in a while, so stay updated!

‍https://rn-evals.vercel.app

Which AI coding model actually writes good React Native code? We couldn't prove it either, so we built a benchmark.

React Native Evals: 43 real-world tasks across animations, async state, and navigation.

Read more on our blog ⬇️ pic.twitter.com/Xmn3GUzFKm

— Callstack Engineers (@callstackio) March 5, 2026

React Native Grab

You know the struggle of steering an LLM for UI changes. It often turns into full project exploration just to tweak a single wording. To make it easier for you, Szymon built a small utility that lets you select an element and copy its location, so an LLM can make surgical changes with minimal tokens. It’s like React Grab but for mobile apps, try it.

Preview release of React Native Grab is now available!
Make your agents stop guessing. Navigate through your app, capture the right context, and let them handle the heavy lifting 💪 pic.twitter.com/upRIfGdDfr

— Szymon Chmal (@ChmalSzymon) March 3, 2026

React Navigation

For React Navigation 8, Satya is experimenting with 2 things:

  • Using React.Activity (will replace experimental freeze)
  • Unmounting inactive screens entirely

It's a bit tricky because navigators can be nested. But hopefully it'll work out.

Last week I was playing with keeping content visible with `<Activity mode="hidden">` and managed to come up with 2 approaches that work on native and web.

Should I write an article about it? pic.twitter.com/sDIdG9if75

— Satyajit Sahoo (@satya164) February 22, 2026

Agent Device

There are a few new things that landed in agent-device since our last update, most notably: native logging, TV support, snapshot (and soon screenshot) diffing, config through a file, and many more. We also crossed 1.1k stars on GitHub, thank you 🙌.

Agents can now easily:

→ analyze a native crash
→ fix it
→ verify the fix without guessing

» npx agent-device@0.6.1 pic.twitter.com/VTPfZngiCs

— Michał Pierzchała (@thymikee) February 22, 2026

React Native Brownfield

Artur, together with Hur, prepared a new version of React Native Brownfield for you. This one is pretty special as it comes with:

  • one-line Expo support with Expo Config Plugin
  • brownfield CLI
  • postMessage API
  • Brownfield Navigation

In a future minor release, the team is also working on Android support for Brownie, our type-safe brownfield state management library.

Introducing React Native Brownfield v3, shipping our Expo Config Plugin 🚀

Package your Expo app and drop it straight into your native iOS & Android apps in minutes using our battle-tested Brownfield approach 📦 pic.twitter.com/AAfUhqwQiC

— Artur Morys-Magiera (@artus9033) February 26, 2026

React Native Sandbox

Aliaksandr found some time lately to finish the React Native Sandbox library by enhancing it with Android support. You can now run isolated JS code inside your React Native app, with guarantees for it not to break your main JS runtime. It’s a pretty powerful abstraction you can build on top of.

@callstack/react-native-sandbox v0.5 is out — now with Android support.

This was by far the most requested feature since first release
Now I'd love to hear your feedback.https://t.co/vNjpZs6NP1#ReactNative #Security #Sandbox

— Aliaksandr Babrykovich (@babrykovich) March 16, 2026

React Native core contributions

  • Add core Yoga support for calc(): a proposal from Kamil for native CSS calc support for Yoga layout engine. This is a pre-requisite for this common CSS feature to work in React Native. It started as a big change to Yoga, but thanks to Nick from the core team we’re able to scope it as a smaller diff to the layout engine without impacting performance, and move more of the implementation to the React Native core (PR there landing soon).

Blog

  • Handling Navigation in React Native Brownfield Apps by Hur Ali: Navigation between React Native and existing native screens can be difficult in brownfield apps. This guide shows how to define a navigation contract, generate native delegates, and connect both layers using @callstack/brownfield-navigation.
  • Announcing React Native Evals by Mike Grabowski, Lech Kalinowski, Piotr Miłkowski, Artur Morys-Magiera & Michał Pierzchała: React Native Evals is a new open-source benchmark from Callstack that evaluates how coding models implement real React Native tasks. The suite ships with 39 evals across animation, async state, and navigation categories, covering libraries like Reanimated, TanStack Query, Zustand, and React Navigation.
  • Keeping Screens Visible With <Activity mode="hidden"> by Satyajit Sahoo: <Activity mode="hidden"> can reduce unnecessary work by unmounting effects for inactive UI trees. But it also hides the UI with display: none, which causes issues for gesture‑driven navigation. This article explores a workaround that keeps screens visible while still freezing effects across native and web.
  • Building Apps Where AI Generates the UI by Mike Grabowski: Most AI apps wrap powerful models in a simple chat interface. This piece explores a different direction: letting the model generate the interface itself. Instead of returning text, it describes what the user should see next. The UI is decided at runtime, adapting to each user and context rather than being hardcoded in advance. The article walks through the architecture behind this pattern and shows it in practice with a project that turns static PDF forms into adaptive, AI-driven interviews.
  • Sparkling: The Missing App Layer for Lynx.js? by Łukasz Chludziński: Lynx.js shipped with a strong brownfield story, but greenfield path felt incomplete. Sparkling changes that by bundling a CLI, native navigation, typed bridge APIs, and platform tooling into one cohesive layer. This article walks through bootstrapping a project, understanding the generated structure, and testing how navigation works in practice.
  • Announcing: React Native Brownfield v3 with Expo Config Plugin by Artur Morys-Magiera & Hur Ali: Moving a large native app to React Native rarely happens in one rewrite. React Native Brownfield v3 combines Expo with an artifact-based packaging approach, so you can ship React Native screens inside your existing app without destabilizing your product.
  • React Native Monorepo With pnpm Workspaces by Nazar Sydiaha: This guide shows how to configure pnpm workspaces for a React Native monorepo that spans mobile and web. It covers pnpm-workspace.yaml, pnpm.overrides, Metro configuration for hoisted deps, and a shared UI package used by both apps.

Videos, and talks

Live streams

  • React Native Evals: Making AI Code Quality Measurable recording & summary
  • OpenClaw, Hermes Node and the State of AI Tooling recording & summary
  • React Native 0.84: Hermes v1, WebAssembly, and Ecosystem Shifts recording

React Universe Summit 2026

React Universe Summit lands in New York City on June 23, 2026, bringing together 200+ CTOs, VPs, and Engineering Directors focused on how AI is reshaping React Native in production.

The day focuses on real delivery data, including velocity, cost, and team output, from teams already using AI across development, CI, testing, and OTA. Sessions cover brownfield adoption, AI’s impact on teams, modular architecture, enterprise infrastructure, and production case studies, with insights from engineers and leaders working at scale.

Book your spot now to join the conversation or reach out to us to discover Partnership Opportunities

Insights

Your next read or watch starts here

Building a Software Factory: Write Specs an Agent Can Build From — cover

Nov 6Article

Building a Software Factory: Write Specs an Agent Can Build From

Learn how to research requirements, resolve open decisions, and write testable specs that AI coding agents can implement without the planning conversation.

 Large-Scale Migrations With Coding Agents: Planning, Verification, and Rollback — cover

Nov 4Article

Large-Scale Migrations With Coding Agents: Planning, Verification, and Rollback

Plan codebase migrations with coding agents using reviewable requirements, verification checks, staged rollouts, and defined rollback criteria.

Conversational Banking: From Customer Questions to Authorized Actions — cover

Nov 2Article

Conversational Banking: From Customer Questions to Authorized Actions

Explore conversational banking architecture through a card-dispute example, covering tool access, authorization, execution, observability, and human handoff.

How AI Agents Can Cut Manual QA by 30% — cover

Oct 30Article

How AI Agents Can Cut Manual QA by 30%

Explore an agentic QA workflow targeting 30% less manual effort across mobile, web, and TV, with test selection, failure triage, and validation.

Building a Software Factory: The Night My Agents Waited for Me — cover

Oct 28Article

Building a Software Factory: The Night My Agents Waited for Me

Learn how permissions, review limits, and missing product decisions stalled two overnight coding agent runs, and how their maintainer revised the workflow.

Your AI Coding Agent Still Needs an Architecture — cover

Oct 22Article

Your AI Coding Agent Still Needs an Architecture

Use explicit contracts, behavior tests, and dependency checks to guide AI coding agents and review their changes through a TypeScript favorites example.

cover

Oct 15Live Stream

Who Left the Agents Running? React Native Software Factories

Join Kewin Wereszczyński and Szymon Chmal to explore what can go wrong in a React Native software factory overnight and the controls that keep agents on track.

cover

Oct 14Podcast

When Coding Gets Faster, What Breaks Next?

Matt Hargett explains how AI moves bottlenecks across testing, deployment, infrastructure, support, and the rest of software delivery.

cover

Oct 13Podcast

MCP and Supervisor Agents in eBay's Monitoring Workflow With Leonel Candido da Silva

Leonel Candido da Silva explains eBay's agentic monitoring workflow: specialized agents, MCP, PagerDuty reports, and plans to learn from past incidents.

cover

Oct 12Podcast

AI Agent Observability With Ivana Huckova and Sven Großmann

Grafana's Ivana Huckova and Sven Großmann discuss AI agent observability, coding-agent costs, PR analytics, secret redaction, and local guardrails.

cover

Oct 7Talk

Automating Mobile QA with Cloud Agents

Michał Pierzchała shows how cloud-based QA agents can test real iOS and Android user flows and bring screenshots, recordings, and logs into pull requests.

cover

Oct 1Live Stream

Can Jev Make AI Agent Decisions Faster?

Explore Jev with Kewin Wereszczyński and Szymon Chmal: how it works, its approach to faster agent decisions, and possible local alternatives.

cover

Mar 19Tutorial

The Hard Way vs. The React Native AI SDK Way: Stop Writing Custom Modules for Every Model

Learn how React Native AI uses a unified provider model to switch between cloud and on-device LLMs without rewriting application logic, enabling reliable AI experiences online and offline.

cover

Mar 12Tutorial

Build Smarter Apps: Tool Calling & AI Orchestration Explained

Learn how on-device models in React Native can call tools, interact with external APIs, and return structured outputs you can use directly in application logic.

cover

Mar 5Tutorial

MLC LLM + React Native: On-Device AI Without the Pain

Learn how to run third-party on-device LLMs in React Native using MLC LLM. Choose your models, run them efficiently across platforms, and keep a unified JavaScript API with React Native AI.

cover

Feb 24Tutorial

Intelligent Fallbacks with Apple Intelligence in React Native

Learn how to use Apple’s built-in Foundation Models in React Native apps, reduce memory usage, and enable fast, fully on-device AI with React Native AI Apple.

cover

Feb 10Tutorial

What Is the React Native AI SDK? A Complete Intro & Quickstart

Learn why on-device AI matters for React Native apps, how local LLMs behave offline, and what problems React Native AI is designed to solve from day one.

cover

Jan 29Tutorial

Implementing an Android TurboModule with Kotlin

Learn how to implement a React Native TurboModule on Android, from the TypeScript spec and Codegen to the Kotlin implementation and package registration.

cover

Jan 19Tutorial

Working with Different Threads in Swift TurboModules

Learn how JavaScript, native module, background, and main threads interact in React Native TurboModules, and how to use GCD queues to run async work safely in Swift.

cover

Jan 9Tutorial

How to Add Type-Safe Constants to Swift TurboModules

Learn how to expose typed, immutable constants from a Swift TurboModule using Codegen, and get full end-to-end type safety between native and JavaScript.

cover

Dec 30Tutorial

Adding Event Emitters to Your TurboModule in Swift

Learn how to emit native events from a Swift TurboModule and subscribe to them in JavaScript, including proper memory management and Codegen integration.

cover

Dec 22Tutorial

Writing Your First TurboModule in Swift

Learn how to build a fully working TurboModule in Swift, integrate it with Codegen, and bridge it through Objective‑C inside an Expo app.