---
title: "Live Dev Session: <Activity>, Expo SDK 54, Router v6, Lynx 3.4, TanStack Start"
description: "A packed week in the React ecosystem: React experiments with a new <Activity> component, Expo SDK 54 speeds up builds, Expo Router v6 adds native-like navigation, Lynx 3.4 ships inputs & dev tools, TanStack Start hits RC, and React Router previews Framework Mode."
url: https://www.callstack.com/events/live-dev-session-week-39
updated: 2026-10-24T08:39:20.833Z
---

# Live Dev Session: <Activity>, Expo SDK 54, Router v6, Lynx 3.4, TanStack Start

A packed week in the React ecosystem: React experiments with a new <Activity> component, Expo SDK 54 speeds up builds, Expo Router v6 adds native-like navigation, Lynx 3.4 ships inputs & dev tools, TanStack Start hits RC, and React Router previews Framework Mode.

_Livestream · 9/25/2025, 5M CEST · Online · Recording: 01:59:36 · Category: Community_

Organizer: Callstack

Speakers: Łukasz Chludziński (Engineering Manager @ Callstack), Kewin Wereszczyński (Software Engineer @ Callstack)

[Watch the recording](https://www.youtube.com/watch?v=4lE1shocwPw)

This week’s livestream was packed with fresh releases, new components, and framework updates across the React ecosystem. From React’s new `<Activity>` component to Expo Router v6 and beyond, there’s a lot for devs to dig into.

Here’s what we covered, why it matters, and where to try it yourself.

## React’s new `<Activity>` component

React is experimenting with a brand new `<Activity>` component. It’s something between conditional rendering and `display: none`:

- Hides parts of the tree without unmounting them
- Preserves state & DOM
- Keeps effects alive
- Deprioritizes rendering to improve app performance

Try it in [the playground](https://react.dev/reference/react/Activity).

**Why it matters:** `<Activity>` is a big step toward giving devs more fine-grained control over rendering without losing app state or introducing unnecessary unmounts. Expect to see more around this as React 19+ continues to roll out.

## Expo SDK 54

Expo 54 is out, and it’s one of the biggest releases of the year. Some highlights:

- Targets Android 16 (API 36) with edge-to-edge layouts always on
- Precompiled React Native binaries → dramatically faster iOS builds
- Transitive autolinking → cleaner native module setup
- Stable object-based file system API → better performance & New Architecture support

Here’s the [full changelog](https://expo.dev/changelog/sdk-54).

**Why it matters:** SDK 54 puts developer experience first: faster iOS builds and fewer native headaches mean smoother iteration, especially on larger apps.

## Expo Router v6

[Expo Router v6](https://expo.dev/blog/expo-router-v6) brings navigation a step closer to a truly native experience. What’s new:

- Link previews (`<Link.Preview>`) → iOS-style peek & pop
- Context menus → richer interactions out of the box
- Server middleware → hybrid SSR/web support
- Liquid glass tab transitions + improved modals

**Why it matters:** Router v6 pushes Expo closer to parity with native navigation, while also bridging into web + SSR territory. It’s becoming more than just a router — it’s a core app architecture piece.

## Lynx 3.4

The Lynx team shipped [a big release](https://lynxjs.org/blog/lynx-3-4) with platform support, core elements, and new dev tools. Highlights:

- HarmonyOS support + full Windows dev environment
- Long-awaited `<input>` and `<textarea>` support
- New Trace (rendering pipeline visualizer) & Recorder (session replay debugger) tools
- Optimized list recycling & improved animations

**Why it matters:** Lynx continues to expand as a cross-platform UI runtime. With proper input support and powerful dev tools, it’s becoming a serious contender for complex apps.

## TanStack Start RC

TanStack Start, the full-stack React framework from the [TanStack team](https://www.callstack.com/podcasts/exploring-tanstack-ecosystem-with-tanner-linsley), is now in [Release Candidate](https://tanstack.com/blog/announcing-tanstack-start-v1).

Features include:

- Built on TanStack Router
- SSR and streaming baked in
- First-class server functions
- Data caching + full-stack integration

**Why it matters:** TanStack has consistently raised the bar for React tooling. Start positions itself as a modern, production-ready full-stack framework with smart defaults and strong performance.

## React Router: RSC Framework Mode preview

React Router is previewing a new [Framework Mode](https://remix.run/blog/rsc-framework-mode-preview) that leans into React Server Components.

**Why it matters:** Framework Mode represents a shift; React Router isn’t just a client router anymore, it’s moving into the RSC-native era with server-first patterns.

## Final thoughts

This was a dense couple of weeks for React devs. `<Activity>` could change how we handle rendering state, Expo 54 and Router v6 are pushing the ecosystem forward, Lynx is becoming more capable, and TanStack + React Router are shaping the next wave of full-stack React.

Catch the livestream replay for demos, examples, and live takes. And as always, huge thanks to the This Week in React crew ([@sebastienlorber](https://twitter.com/sebastienlorber), [@tboba\_](https://twitter.com/tboba_), and [@piaskowyk](https://twitter.com/piaskowyk)) for sharing insights and context.