Articles

Articles for developers, by developers

Technical articles on React, React Native, and AI engineering. We share what we learn from building products, maintaining open source, and putting agents to work across software delivery.

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Performance
5/21/2025

Multithreading Isn’t Free: Performance Pitfalls Visualized

This article walks through real-world examples of profiling multithreaded C++ code. It shows what happens when you throw too many threads at a problem, how to measure performance with Tracy, and why smarter scheduling beats brute force. While the code is in C++, the takeaways apply to any performance-critical system.

Mariusz Pasiński

Software Engineer

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Callstack

AI
5/15/2025

Meet react-native-ai: LLMs Running on Mobile, for Real

Running AI models locally in React Native used to sound impossible, but not anymore. This post introduces react-native-ai, a new library powered by MLC and integrated with Vercel AI SDK, enabling on-device LLM inference with a web-like API and native performance.

Szymon Rybczak

Software Developer

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Callstack

Super Apps
5/14/2025

New in Re.Pack 5.1: Preloading Remotes, Runtime Hooks, and Faster Startups

This release of Re.Pack adds runtime hooks for customisation of script loading, support for prefetching of Module Federation 2 remote modules, and experimental faster hot startups via persistent cache. It also ensures full compatibility with React Native 0.79 and improves support for module resolution with Package Exports.

Jakub Romańczyk

Software Engineer

@

Callstack

Security
5/13/2025

React Native Legal: Zero-Config OSS License Screens for Your App

Open-source libraries power all React Native apps, but many devs overlook the need to acknowledge them inside the app itself. This post introduces React Native Legal, a zero-config tool that generates license metadata and adds a native-style license screen across iOS, Android, tvOS, and AndroidTV.

Michał Pierzchala

Principal Engineer

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Callstack

Brownfield
4/28/2025

Powering Native Apps with React Native Brownfield

This article introduces the brownfield approach, explaining how it allows you to bring React Native into existing native apps without starting from scratch. It then covers how our library, React Native Brownfield, simplifies this process by embedding React Native screens into native apps, and provides an overview of its structure and key features.

Burak Güner

Software Developer

@

Callstack

Performance
4/11/2025

Profiling React Native Internals with Tracy for Peak Performance

Profiling React Native's internals can uncover bottlenecks and provide deep insights into native behavior. This guide walks through using the Tracy profiler to instrument React Native code, collect performance metrics, and identify optimization opportunities across iOS and Android.

Mariusz Pasiński

Software Engineer

@

Callstack

Performance
3/20/2025

Why Knowing Your App’s Bundle Contents Matters for React Native Performance

Slow app startup times can frustrate users, especially on older devices or slower networks. Expo Atlas helps you peek inside your React Native app bundle to identify large dependencies and optimize performance, even if you're not using Expo.

Szymon Chmal

Software Developer

@

Callstack

Enterprise
3/14/2025

We’re Building a New React Native Framework

Building large React Native apps can be challenging, with slow build times, complex integrations, and mixed tech stacks. We're developing a new framework designed for enterprise apps that optimizes build reuse, CI speed, and cloud integration while staying flexible and self-hosted.

Michał Pierzchala

Principal Engineer

@

Callstack

AI
3/11/2025

Local LLMs on Mobile Are a Gimmick-For Now

Running large language models directly on mobile devices is currently limited by model size, format compatibility, and performance trade-offs. However, tools like MLC are emerging to simplify the process and pave the way for a future where everyone has their own AI assistant in their pocket.

Kewin Wereszczyński

Software Engineer

@

Callstack

Super Apps
2/27/2025

Re.Pack 5: Mobile Microfrontends, 5x Faster, Less Configuration

We are thrilled to announce the release of Re.Pack 5, our biggest update ever. This milestone release represents a complete transformation of our build tool for React Native applications, bringing unprecedented performance improvements through Rspack, proper microfrontends support through Module Federation 2, simplified configuration and more!

Jakub Romańczyk

Software Engineer

@

Callstack

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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.

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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.

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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.

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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.

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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.

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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.

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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.

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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.

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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.

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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.

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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.

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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.

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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.

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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.

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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.

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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.

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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.