Expert engineering

Build and scale React Native apps.

For over a decade, enterprise teams have trusted us with React and React Native products. Our senior engineers work with AI agents on new builds, complex migrations, and native engineering.

Trusted by 100+ Enterprise clients

Feature Development

Ship priority features with React and React Native experts.

Senior product engineers join your team to clear backlog, ship roadmap work, and take high-impact implementation off your internal leads. AI-native delivery lets a small expert team cover more ground without lowering your bar for review, testing, or architecture.

Team Training

Build stronger engineering teams.

We run targeted, hands-on training around your codebase, engineering goals, and delivery constraints. Programs cover React and React Native fundamentals, architecture, performance, production patterns, and AI-assisted workflows.

Expert engineering

Bring us your engineering challenge.

Our engineers can join your team, take on a defined project, or help you adopt agents across development, testing, and release. Tell us what you're working on.

How we work together

Engineering support that fits your team.

  1. Extend your team

    Our senior engineers join your team to ship features, guide technical decisions, and strengthen delivery.

    • Your roadmap and workflow
    • Expertise shared as we work
    • Flexible timezone coverage
  2. Deliver a project

    We take agreed work from technical planning to release, with clear responsibilities and progress you can see.

    • 3 Callstack engineers ship like 6
    • Impact visible before sprint two
    • End-to-end delivery
  3. Solve specific challenge

    We address a performance, migration, or infrastructure challenge, or run training around your team’s needs.

    • Focused reviews or implementation
    • Knowledge your team keeps
    • Outcomes guaranteed with contract
React Foundation Founding Member
300+ commits to React Native
100+
Enterprise projects delivered
Industry runs on our tooling
50M+
OSS downloads / month
3.7×
Lower task cost vs Opus 5.5
I recommend them as a trusted tech partner for running complex projects.
Jin Chung
Co-Founder, CTO / Rainbow
5x
Faster message sending time
ISO 27001 certified

EXPERT ENGINEERING · AGENTIC DELIVERY

Put our expertise to work.

Our engineers can join your team, take on a defined project, or help you adopt agents across development, testing, and release. Tell us what you're working on.

Open Source

Build with our open-source tools.

We open-source the tools behind our delivery model.
Use them, fork them, or let us run them for you.

React Native Brownfield

Incrementally move your iOS and Android apps to React Native without breaking

552 stars

React Native Testing Library

Simple and complete React Native testing utilities that encourage good testing practices

18.2M downloads/mo

React Native Builder Bob

Simple set of CLIs to scaffold and build React Native libraries for different targets

1.4M downloads/mo

React Native Pager View

React Native wrapper for the Android ViewPager and iOS UIPageViewController

5.5M downloads/mo

React Native AI

On-device LLM execution in React Native with Vercel AI SDK compatibility

227.7K downloads/mo

Re.Pack

A webpack-based toolkit to build your React Native application with full support of webpack ecosystem

2.2M downloads/mo

React Native Bottom Tabs

Native Bottom Tabs for React Native

408.8K downloads/mo

Liquid Glass

iOS Liquid Glass in React Native

539.2K downloads/mo

Insights

Worth your time, by engineers.

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Apr 2Webinar

AI-Assisted Migrations to React Native: From Months to Days

Reduce migration time from months to days by using AI in real React Native workflows. Learn when to migrate incrementally and when starting fresh is the better option.

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Mar 3Article

Building Apps Where AI Generates the UI

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.

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Jan 12Podcast

Building v0 iOS and Fixing React Native Along the Way

A technical look at building v0 mobile with React Native and Expo, covering iOS-first decisions, native modules, and fixes pushed to React Native core. Featuring Fernando Rojo, Szymon Rybczak, and Oskar Kwaśniewski.

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Mar 24Article

From Brownfield Complexity to AI-Supported React Native Migration

Brownfield migrations often fail due to ordering and integration gaps, not framework limits. This article explains how an AI-supported workflow helps enforce correct sequencing across packaging, startup, and runtime validation.

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Feb 17Podcast

From Teddy Bears to Voice Agents: Kraen Hansen on Voice AI, Local-First & App Security

What happens when you combine voice agents and teddy bears? A hands-on look at local-first systems, voice AI, and security lessons from poking real apps.