Software Engineer

Kewin Wereszczyński

Kewin Wereszczyński

Started his career as a tester before transitioning into programming, working on numerous startup projects as a solo frontend developer or in small teams. His biggest achievement was becoming a frontend lead on one of the projects. Passionate about 3D graphics, games, special effects, photography, and cinematography, he has also explored being a rock band vocalist, English stand-up performer, improviser, and YouTuber. Recently, he has become a bit obsessed with AI.

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What I’ve been shipping

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Article
7/21/2025

Performant and Cross-Platform Shimmers in React Native Apps

A modern shimmer library for React Native with smooth UI skeletons, minimal dependencies, and optimized performance using Reanimated and SVG. Drop-in ready with full customization and shared animation state.
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Article
6/4/2025

How I Used MCP to Control My Friend's Home

Learn how MCP works with a hands-on project that connects Claude AI to smart home data using a Node.js server.
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Article
5/28/2025

Want to Run LLMs on Your Device? Meet MLC

Find out how MLC compiles both model and runtime for efficient local LLM inference, and what that means for running AI on your Android or iOS app.
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Article
3/11/2025

Local LLMs on Mobile Are a Gimmick-For Now

Can local LLMs replace cloud-based AI? We analyze performance, limitations, and the future of on-device AI models in 2025.
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Article
2/4/2025

Giving AI The Keys to Your App: Agents Controlling UI State

Learn how to let AI agents control UI state in React using Jotai and Flows-AI, automating logic and workflows for smarter, autonomous applications.
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Article
1/17/2025

Building AI Agent Workflows With Vercel’s AI SDK: A Practical Guide

Learn to build AI Agent workflows with Vercel's AI SDK. Explore chaining, routing, parallel & evaluator-optimizer patterns.
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Article
12/1/2023

Creating a Video Transcription App: Lessons Learned

Read about Callstack's R&D journey into AI for a transcription app, using OpenAI's Whisper for speech recognition. Discover the lessons learned.
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podcast
11/25/2024

Building a Custom AI Assistant for Your Business

Learn what it takes to build a custom AI-powered chatbot for your company, including the challenges, solutions, performance, and security considerations.
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Webinar
Live Stream
6/18/2026

How to Teach Your Own AI Model?

Join Piotr Miłkowski on June 18 at 17:00 to explore AI training, datasets, model mistakes, APIs, and beginner-friendly projects.
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Event
Webinar
Live Stream
5/28/2026

Redraw and the Future of 2D Graphics on WebGPU

Join Callstack engineers Szymon Chmal and Kewin Wereszczyński on May 21 at 5 PM to explore Redraw, a new 2D graphics library for WebGPU.
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Event
Webinar
Live Stream
5/14/2026

Testing AI Agent Skills Reliably With Skill Gym

Learn how Skill Gym helps test, validate, and improve AI agent skills with repeatable workflows, assertions, and model-aware feedback.
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Event
Webinar
Live Stream
5/7/2026

Improve Your AI Coding Workflow With Cursor Tips and Tricks

Explore practical tips for working with AI coding agents, managing context, using skills, reviewing code, and choosing the right models.
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Webinar
Live Stream
4/30/2026

Build a React Native App With the TanStack Stack

Join Callstack’s live stream on building a React Native app from the ground up using the TanStack toolbelt.
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Event
Webinar
Live Stream
4/16/2026

React Native 0.85: Animation Backend and Key Updates

A recap of React Native 0.85, covering the new animation backend, DevTools improvements, and ecosystem takeaways.
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Event
Webinar
Live Stream
3/26/2026

Expo UI with SwiftUI and Jetpack Compose in practice

Exploring Expo UI with SwiftUI and Jetpack Compose, including setup challenges, architecture tradeoffs, and real-world developer insights.
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Event
Webinar
Live Stream
3/19/2026

Agent Device, AI workflows, and mobile testing in practice

A discussion on Agent Device, AI-driven workflows, and testing mobile apps using simulators and accessibility data.
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Event
Webinar
Live Stream
3/12/2026

React Native Evals: Measuring AI Code Quality in Practice

React Native Evals introduces a data-driven way to measure how AI coding models perform on real React Native development tasks.
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Event
Webinar
Live Stream
2/26/2026

OpenClaw, Hermes Node and the State of AI Tooling

Kewin Wereszczyński and Daniel Williams discuss OpenClaw, Hermes Node, Markdown rendering, AI coding tools and the current AI landscape
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Event
Webinar
Live Stream
2/19/2026

React Native 0.84: Hermes v1, WebAssembly, and Ecosystem Shifts

React Native 0.84 introduces Hermes v1 by default, iOS prebuilt binaries, WebAssembly support, and improved tooling across the ecosystem.
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Event
Webinar
Live Stream
2/12/2026

Sparkling: A New Framework for Lynx

Join the Lynx team live as we explore Sparkling, its boundaries with Lynx, core features, and bootstrap a project from scratch.
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Event
Webinar
Live Stream
2/5/2026

Storybook Explained: From Basics to Advanced Workflows

Core Storybook concepts, stories and args, interaction testing, and how Storybook works in React Native projects.
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Event
Webinar
Live Stream
1/29/2026

Exploring Skills in Claude: A Live Walkthrough

Live experiments with Claude Skills in a React Native codebase, covering AI agents, Expo upgrades, and practical limits of automation
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Event
Webinar
Live Stream
1/22/2026

React and React Native Weekly Breakdown

Join Callstack engineers for a live discussion on this week’s most important React and React Native updates, trends, and ecosystem shifts.
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Event
Webinar
Live Stream
1/15/2026

React and React Native in 2026: Architecture, Nitro, and What’s Next

New architecture adoption, Nitro modules, React Strict DOM, Hermes v1, and ecosystem shifts shaping React and React Native in 2026.
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Event
Webinar
Live Stream
12/18/2025

Building iOS Live Activities With React: Inside Voltra

Learn how to build iOS Live Activities and Dynamic Island experiences using pure JSX, no Swift or native code required.
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Event
Webinar
Live Stream
12/11/2025

React Native 0.83: A Stability-Focused Release With Surprisingly Big Quality-of-Life Wins

Join Łukasz Kewin for a walkthrough of React Native 0.83, recent ecosystem news, and hands-on demos.
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Event
Webinar
Live Stream
12/4/2025

React Native on Meta Quest: What We Learned About Building for VR

See Meta Quest used as a practical dev setup and watch the team build and test React Native features directly inside a VR workspace.
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Event
Webinar
Live Stream
12/2/2025

Two Threads of Lynx.js Part 2

Learn how Lynx.js uses a dual-threaded model, how its APIs work, and what it means for performance in this live session with Lukasz Chludzinski and Kewin Wereszczynski.
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Event
Webinar
Live Stream
11/27/2025

Exploring Lynx.js and Its Two-Thread Runtime

A recap of our live session exploring how Lynx.js splits work across a main thread and a background thread.
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Event
Webinar
Live Stream
11/13/2025

Inside Valdi: What We Learned Exploring Snapchat’s New UI Framework

A hands-on look at Valdi, Snapchat’s new UI framework: setup, architecture, rendering model, and early developer impressions.
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Webinar
Live Stream
10/30/2025

Reanimated, TanStack, Cross-Pollinating Languages & TWIR #256 Anniversary

Catch up on everything from TanStack updates and Astro insights to Reanimated deep dive and even Swift for Android. Plus, we celebrate the 256th newsletter!
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Webinar
Live Stream
11/20/2025

Introducing Solito 5 and the Web-Native Mindset

Join us on November 20 for a deep dive into Solito 5 with its creator, Fernando Rojo, and the Callstack team.
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Webinar
Live Stream
10/23/2025

Building Real-Time Live Activities in Expo

Learn how to add real-time LiveActivity updates to your Expo app using Swift native modules. In this stream, we implemented Apple’s Live Activities with Evan Bacon’s library, explored ActivityKit, and discussed cross-platform development with Solito 5 and Expo UI.
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Webinar
Live Stream
10/16/2025

React Native Harness, Next.js 16 Beta & Remix v3

This week’s Live Dev Session dives into React Native Harness with Szymon Chmal, explores the Next.js 16 Beta and Remix v3 “pre-drop,” and breaks down the biggest React and React Native updates from the community and React Alicante 2025.
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Event
Webinar
Live Stream
10/9/2025

React Native Conf 2025: React Foundation, Compiler 1.0 & Future of React Native

React Native Conf 2025 brought huge announcements: React Foundation under Linux Foundation, React Compiler 1.0 and Hermes v1. What’s next for React Native and newest React Features.
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Event
Webinar
Live Stream
10/2/2025

Building React Native App for Vega OS

React 19.2 brings <Activity> and useEffectEvent, new ideas for React state management arrive, and Vega OS debuts as a React Native-powered Linux OS.
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Webinar
Live Stream
9/25/2025

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.
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9/11/2025

Live Dev Session: React Universe Conf, RN 1.0, Expo Updates & More

In Week 37 of our Live Dev Session we talked about React Universe Conf with guest Szymon, ranted about AI, explored what React Native 1.0 really means, reviewed Expo updates, and covered the latest moves in the React Native ecosystem.
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Webinar
Live Stream
8/28/2025

Live Dev Session: Routers, React Native AI, and Expo Launch

Nuqs 2.5, Remix v3, Expo Launch, SPM support in React Native, the Jest RFC, and native Text-to-Speech with guest insights from Mike Grabowski.
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Webinar
Live Stream
8/21/2025

Live Dev Session: Expo SDK 54 Beta Is Here, Next.js 15.5, RNEF Renamed Rock

Explore what's new in Expo SDK 54 Beta: Liquid Glass, faster iOS builds, RN 0.81, and more dev upgrades from this week's livestream.
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Webinar
Live Stream
8/7/2025

Live Dev Session: FlashList v2, Vercel AI SDK, React Compiler

This week's livestream highlighted two major releases reshaping the React and React Native landscape: FlashList v2 and Vercel AI SDK 5.
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Event
Webinar
Live Stream
7/31/2025

Live Dev Session: Rozenite DevTools Plugins Framework, Precompiled React Native for iOS, TanStack DB 0.1

Discover Rozenite: DevTools framework for React Native, faster iOS builds, on-device AI, and key updates from this week’s livestream.
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Webinar
Live Stream
7/24/2025

Live Dev Session: Reanimated 4, Worklets, React Native Screens

This week was packed with insights on highly anticipated Reanimated 4, the power of Worklets, Screens and more.
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Webinar
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7/16/2025

Live Dev Session: Node-API, Wallets & Worklets in React Native

Node-API in RN, Apple’s LLM, react-native-wallet, ChromeOS rumors. The Week 29 React Native stream breaks it all down with some code and a lot of commentary.
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7/10/2025

Live Dev Session: Unistyles 3.0, SSR With Hermes & Expo SDK 52

From inside shadows to decentralized music players, catch the latest React Native takes in Week 28 live dev session with Łukasz, Kewin, and Mike.
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Webinar
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7/3/2025

Live Dev Session: Exploring Skia, Nitro Modules & UI Playgrounds

Live dev stream exploring Skia, Nitro Modules, AI app builders, and React Native tools; plus side quests into canvas UIs, Lottie, and pizza-coded joy.
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6/17/2025

Live Dev Session: React Native Styling, OTA, and UI Tools

Tune in to a live session unpacking React Native 0.80, OTA alternatives, AI-generated UIs, styling wars, and some truly wild tech tangents.
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6/10/2025

Live Dev Session: First Impressions of Apple’s On-Device AI

Tune in to dev chat on Apple’s AI SDK, iOS 26 naming chaos, Siri’s limits, Liquid Glass UI, and on-device LLMs.
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6/3/2025

Run LLMs Locally With React Native & MLC

Watch how MLC brings on-device AI to React Native. See react-native-ai in action and discover what’s next for local model execution.
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