Bring your next engineering challenge.

Work with engineers behind widely used open-source tools. We build and scale products across platforms, and help your teams deliver more with AI.

Highlights

3.7×
Lower React Native task cost vs Claude Opus 5.5
$0.50
1M input tokens
$3.00
1M output tokens
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import { generateText } from "ai"

const { text } = await generateText({
model: "apex",
prompt: "Ship this React Native screen.",
})
Check Apex
Apex: 3.7× lower React Native task cost.
Scored 87.8% versus Claude Opus 5.5’s 88.6% on React Native evals. Run Apex inside your existing coding tools.
5x
Faster message sending time
5x faster message sending for Expensify.
Search screens loaded 4.5× faster, too. We added continuous performance checks to catch regressions.
3x
Delivery acceleration
70
Pages in 3 weeks
80%
Effort executed by agents
Agentic delivery: up to 3x estimated acceleration.
Agents executed an estimated 80% of development effort. Engineers owned architecture, review and release.
Built on Agent Device.
Check Agent Device
Let agents verify the apps they build.
Our open-source tool lets agents inspect, control and verify apps on real devices. 4,900+ GitHub stars.
~6x
Faster prototyping
60+
Components mapped with full coverage
Read case study
~6x faster screen prototyping with AI.
From about an hour to around 10 minutes for a typical enterprise screen, using a shared design system across web and mobile.
10 min
From code change to mini-app release
Teamworks: mini-app releases in ~10 min.
Re.Pack helped seven mini-apps ship independently. Their previous delivery process took 1–2 days for even small updates.

Why Callstack

Work with React Native Core Contributors with 100+ enterprise clients and open-source libraries downloaded 50M+ times every month.

↳ Expert engineering

We help you launch on more platforms, modernize existing apps, and solve performance and native engineering problems.

↳ Agentic delivery

We bring agents into your software lifecycle so your teams can ship more.

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

Faster message sending time

ISO 27001 certified

Case studies

What shipping at AI speed looks like.

Expert EngineeringFinance
Enhancing Expensify app performance
5x
faster message sending time
Expert EngineeringFinance
Migrating Questrade Edge Mobile to a Faster, More Scalable Architecture
33%
fewer re-renders across most features
Expert EngineeringSports & Entertainment
Teamworks cut mobile change lead time from days to minutes
10
min from code change to mini-app release
Agentic DeliverySoftware Development
Building an Agentic SDLC for a Web Launch in Under One Month
3x
estimated delivery acceleration

Clients

Trusted by enterprise teams at scale.

The team at Callstack are the most experienced engineers in the React Native community.
Nader Dabit
Senior Developer Advocate / AWS
If you're looking for skilled and trusted React Native developers, Callstack is definitely the way to go.
Tom Occhino
Director of Engineering / Meta
Their engineers proved to be a crucial part of our mobile app relaunch project.
Brian Aznar
Engineering Director / MLS
The trainers are always very helpful and supportive. It really makes a difference!
Artem Musiienko
Staff Eng / Hello Fresh
I appreciate their attention to detail, flexible approach and a high degree of expertise.
Glen Moriarty
Founder and CEO / 7cups
We had been struggling with React Native application performance until we met Callstack.
Huỳnh Chí Hùng
Associate Director / MoMo
I recommend them as a trusted tech partner for running complex projects.
Jin Chung
Co-Founder, CTO / Rainbow
Teamworks needed Module Federation, we helped make it real
Michael Song
Head of Platform / Teamworks
Not only does Callstack have tremendously talented engineers, but I know they care about the success of the project as much as I do.
TC Davis
Product / Expo

10 years of React Native → Now in your AI stack

Ship your product at AI speed.

Senior engineers and agents, building cross-platform products faster without lowering the bar. Let's scope what that looks like for your team.

Book consultation

Insights

Worth your time, by engineers.

ArticleOct 16, 2026

React Native Wrapped 2025: A Month-by-Month Recap of The Year

The first edition of React Native Wrapped looks back at the year RN turned 10 and the ecosystem doubled down on the New Architecture. It provides a month-by-month record of 2025, covering major framework releases, the Legacy Architecture freeze, React 19 integration, and notable developments across tooling, performance, styling, native modules, Expo, and platform adoption.