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Oskar

@o_kwasniewski • 11,178 subscribers

Co-Founder / CTO @TesterArmy (YC P26), previously @callstackio

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Here are two Liquid Glass effects: one made with React Native and the other with SwiftUI. Can you tell which is which? 👀

Here are two Liquid Glass effects: one made with React Native and the other with SwiftUI. Can you tell which is which? 👀

639,951 views

The first version of React Native Vision OS is out! 🎉🥽 You can init your project using this command: `npx @callstack/react-native-visionos init MyApp` We are still in the early stages of development. If you encounter any bugs, please don't hesitate to open a new issue 🙏

The first version of React Native Vision OS is out! 🎉🥽 You can init your project using this command: `npx @callstack/react-native-visionos init MyApp` We are still in the early stages of development. If you encounter any bugs, please don't hesitate to open a new issue 🙏

279,008 views

React Native Bottom Tabs v0.9.2 is out! ✨ - Tabs are now properly working on iOS 26 🚀 - Measure custom tab bars (for useBottomTabBarHeight) 📏 - Initial layout fixes 📱 Check it out:

React Native Bottom Tabs v0.9.2 is out! ✨ - Tabs are now properly working on iOS 26 🚀 - Measure custom tab bars (for useBottomTabBarHeight) 📏 - Initial layout fixes 📱 Check it out:

119,150 views

I just released NoteScan - a dead simple app for people who think on paper ✍️ Point camera → AI reads handwriting → Copy text. That's it. Built with Expo and Gemini 3 Flash. Here is a demo 👇🏻

I just released NoteScan - a dead simple app for people who think on paper ✍️ Point camera → AI reads handwriting → Copy text. That's it. Built with Expo and Gemini 3 Flash. Here is a demo 👇🏻

72,728 views

v0.10.0 is out! 🚀 🆕 Easily upload files to device and open the filesystem in Finder. Works on both Android and iOS 🔥 Huge thanks to xjki for contributing this feature!

v0.10.0 is out! 🚀 🆕 Easily upload files to device and open the filesystem in Finder. Works on both Android and iOS 🔥 Huge thanks to xjki for contributing this feature!

57,139 views

React Native Bottom Tabs 1.0.0 is out ✨ - Drops old architecture 🌅 - Simplifies build configuration, making it fully compatible with Expo Image ✅ - Bunch of bug fixes 🐛 It works with Expo router, React Navigation and in standalone mode ⬇️

React Native Bottom Tabs 1.0.0 is out ✨ - Drops old architecture 🌅 - Simplifies build configuration, making it fully compatible with Expo Image ✅ - Bunch of bug fixes 🐛 It works with Expo router, React Navigation and in standalone mode ⬇️

76,602 views

Introducing (React) Native Bottom Tabs! 🎉 First Bottom Tab Navigator using Native Platform primitives for both Android and iOS. The API surface is almost a drop-in replacement for JS Bottom Tabs! ➡ `npm i react-native-bottom-tabs`

Introducing (React) Native Bottom Tabs! 🎉 First Bottom Tab Navigator using Native Platform primitives for both Android and iOS. The API surface is almost a drop-in replacement for JS Bottom Tabs! ➡ `npm i react-native-bottom-tabs`

82,860 views

constantly iterating on TesterArmy (YC P26) landing page design ✨

constantly iterating on TesterArmy (YC P26) landing page design ✨

22,985 views

New version of @⁠callstack/liquid-glass has been released! This one makes use of the new iOS 26 API for border radius, making it compatible with context menus from Zeego 🔥 You can now achieve this awesome merge effect ⬇️

New version of @⁠callstack/liquid-glass has been released! This one makes use of the new iOS 26 API for border radius, making it compatible with context menus from Zeego 🔥 You can now achieve this awesome merge effect ⬇️

23,299 views

new TesterArmy (YC P26) landing page just dropped 👀

new TesterArmy (YC P26) landing page just dropped 👀

13,340 views

New release of `react-native-bottom-tabs`! 🚀 This one includes a new Expo Config plugin that sets the correct styling for tabs on Android! 🤖 Here is a demo of Expo SDK 52 + Expo Router on New Architecture:

New release of `react-native-bottom-tabs`! 🚀 This one includes a new Expo Config plugin that sets the correct styling for tabs on Android! 🤖 Here is a demo of Expo SDK 52 + Expo Router on New Architecture:

36,481 views

Lately, I’ve been tightening my agentic coding loop - making sure what my coding agent ships actually works. Today I built a small CLI: ⁠𝚛𝚗-𝚕𝚘𝚐𝚜 🔍 It connects via CDP to pull React Native Metro logs allowing your agent to see what's going on. Here is a small demo ⬇️

Lately, I’ve been tightening my agentic coding loop - making sure what my coding agent ships actually works. Today I built a small CLI: ⁠𝚛𝚗-𝚕𝚘𝚐𝚜 🔍 It connects via CDP to pull React Native Metro logs allowing your agent to see what's going on. Here is a small demo ⬇️

14,930 views

A new version of React Native Bottom Tabs 0.8.0 is out! 🎉 Lots of work went into this release: - Complete refactoring of Android view management ♻️ - New Android Page Transitions ✨ - Material You support 🎨 - Other bug fixes 🔧

A new version of React Native Bottom Tabs 0.8.0 is out! 🎉 Lots of work went into this release: - Complete refactoring of Android view management ♻️ - New Android Page Transitions ✨ - Material You support 🎨 - Other bug fixes 🔧

27,887 views

React Native Bottom Tabs 0.5.0 is out 🚀🎉 - SVG Support 🖼️🥳 - Remote icon assets 🌐 - Custom fonts, label styles 🎨 - Bug fixes 🐛

React Native Bottom Tabs 0.5.0 is out 🚀🎉 - SVG Support 🖼️🥳 - Remote icon assets 🌐 - Custom fonts, label styles 🎨 - Bug fixes 🐛

28,135 views

Looks like we can place UIKit views in the accessory view! 🚀 Here is a small demo of iOS 26 accessory view running with React Native Bottom Tabs 🔥 Time to think about a good API for this 😄

Looks like we can place UIKit views in the accessory view! 🚀 Here is a small demo of iOS 26 accessory view running with React Native Bottom Tabs 🔥 Time to think about a good API for this 😄

18,361 views

Here is an example of using multiple windows on iPadOS with React Native! ✨ Thanks to React Native Factory integrating this became a lot easier and now I'm working on first-party support for this feature! 👀

Here is an example of using multiple windows on iPadOS with React Native! ✨ Thanks to React Native Factory integrating this became a lot easier and now I'm working on first-party support for this feature! 👀

21,638 views

Bottom Accessory view is coming soon to React Native Bottom Tabs! 🚀 Huge thanks to Johan Kasperi for contributing this 🙏 This looks so cool ⬇️

Bottom Accessory view is coming soon to React Native Bottom Tabs! 🚀 Huge thanks to Johan Kasperi for contributing this 🙏 This looks so cool ⬇️

14,743 views

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e2e + jev from TypeSafe AI ⚡ I'm building an open-source framework for running e2e tests with agents. supports web, mobile (and more!) available soon:
1:09
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e2e + jev from TypeSafe AI ⚡ I'm building an open-source framework for running e2e tests with agents. supports web, mobile (and more!) available soon:

Oskar

69,772 views • 29 days ago

this is what AUTOMATED UI testing looks like
0:25
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this is what AUTOMATED UI testing looks like

Oskar

307,585 views • 5 months ago

Built a test suite for T3 Code with e2e ⚡ 40 tests, testing 6 coding agents (Codex, Claude, Grok, OpenCode, Pi, Antigravity) mocked at CLI level It already caught a small bug: Stop doesn't stop a turn that's still starting
1:20
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Built a test suite for T3 Code with e2e ⚡ 40 tests, testing 6 coding agents (Codex, Claude, Grok, OpenCode, Pi, Antigravity) mocked at CLI level It already caught a small bug: Stop doesn't stop a turn that's still starting

Oskar

22,296 views • 12 days ago

Jev from Cloudflare just dropped (klef) 👀 Here is a demo of klef + e2e (open source AI testing framework). Klef drives an e2e test through a mix of vision and accessibility APIs.
0:36
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Jev from Cloudflare just dropped (klef) 👀 Here is a demo of klef + e2e (open source AI testing framework). Klef drives an e2e test through a mix of vision and accessibility APIs.

Oskar

27,049 views • 15 days ago

e2e blow up on X yesterday. I recorded a quick video on the philosophy behind the framework, how it fits into your software development workflow, and what you can build with it. ~/ npx e2e init
6:00
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e2e blow up on X yesterday. I recorded a quick video on the philosophy behind the framework, how it fits into your software development workflow, and what you can build with it. ~/ npx e2e init

Oskar

24,558 views • 15 days ago

e2e + agent device ✨ testing mobile apps with agents should be simple and reliable more coming soon
0:25
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e2e + agent device ✨ testing mobile apps with agents should be simple and reliable more coming soon

Oskar

54,204 views • 1 month ago

crazy that people still test onboarding by hand
0:30
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crazy that people still test onboarding by hand

Oskar

53,933 views • 5 months ago

this is what AGENTIC UI testing looks like
0:47
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this is what AGENTIC UI testing looks like

Oskar

38,351 views • 5 months ago

In January I released NoteScan - a dead simple app for people who think on paper✏️ Now the app has over 1K+ downloads and people are loving it! ✨ If you write by hand, you need this.
0:26
o_kwasniewski's profile picture

In January I released NoteScan - a dead simple app for people who think on paper✏️ Now the app has over 1K+ downloads and people are loving it! ✨ If you write by hand, you need this.

Oskar

22,810 views • 7 months ago

The new version of React Native Bottom Tabs is out! 🎉 A new highly anticipated feature: Custom JavaScript Tabs! ✨ Provide your custom tab bar while leveraging native navigation underneath 🚀 Here is a demo of it in the 🦋 app! This demonstrates smooth screen transitions using native animations along with their custom tab bar.
0:21
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The new version of React Native Bottom Tabs is out! 🎉 A new highly anticipated feature: Custom JavaScript Tabs! ✨ Provide your custom tab bar while leveraging native navigation underneath 🚀 Here is a demo of it in the 🦋 app! This demonstrates smooth screen transitions using native animations along with their custom tab bar.

Oskar

35,844 views • 1 year ago

Introducing React Native Emoji Popup 🌈 Emoji Picker that uses native primitives ⚡ I've created it for a side-project I'm working on and decided to open-source it✨
0:29
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Introducing React Native Emoji Popup 🌈 Emoji Picker that uses native primitives ⚡ I've created it for a side-project I'm working on and decided to open-source it✨

Oskar

24,316 views • 1 year ago

React Native WebGPU on visionOS! 🥽 A few weeks ago William Candillon released React Native react-native-webgpu and we've managed to run it on visionOS! 🎉 PR is still WIP but this looks awesome 🤩 Great job William Candillon, Krzysztof Piaskowy 👏
0:39
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React Native WebGPU on visionOS! 🥽 A few weeks ago William Candillon released React Native react-native-webgpu and we've managed to run it on visionOS! 🎉 PR is still WIP but this looks awesome 🤩 Great job William Candillon, Krzysztof Piaskowy 👏

Oskar

28,644 views • 2 years ago

🪄 Cali: An AI agent for building React Native apps This tool is so simple yet so powerful, can help you with bunch of things while building your React Native apps (more coming soon!) ➡️ npx cali Hacked together with Mike this weekend 😄🚀
0:24
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🪄 Cali: An AI agent for building React Native apps This tool is so simple yet so powerful, can help you with bunch of things while building your React Native apps (more coming soon!) ➡️ npx cali Hacked together with Mike this weekend 😄🚀

Oskar

17,707 views • 1 year ago

What is the difference between React Native JS Bottom Tabs and Native Bottom Tabs? 👀 Native bottom tabs use native platform primitives to render tabs (TabView from SwiftUI and BottomNavigationView on Android), while JS Tabs recreate this UI as closely as possible. This approach works well but tabs can have different appearances on different platforms, here is an example:
0:40
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What is the difference between React Native JS Bottom Tabs and Native Bottom Tabs? 👀 Native bottom tabs use native platform primitives to render tabs (TabView from SwiftUI and BottomNavigationView on Android), while JS Tabs recreate this UI as closely as possible. This approach works well but tabs can have different appearances on different platforms, here is an example:

Oskar

15,843 views • 2 years ago

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