--- title: "React & React Native Experts | Agentic Delivery | Callstack" description: "Callstack builds and scales React and React Native products, and helps teams deliver with AI agents, custom workflows, and testing they control." url: https://www.callstack.com updated: 2026-11-09T15:49:08.524Z --- # React & React Native Experts | Agentic Delivery | Callstack Callstack builds and scales React and React Native products, and helps teams deliver with AI agents, custom workflows, and testing they control. ## 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 ### [Apex: 3.7× lower React Native task cost.](https://apex.callstack.com) Scored 87.8% versus Claude Opus 5.5’s 88.6% on React Native evals. Run Apex inside your existing coding tools. 3.7× Lower React Native task cost vs Claude Opus 5.5 · $0.50 1M input tokens · $3.00 1M output tokens ### [5x faster message sending for Expensify.](https://www.callstack.com/case-studies/enhancing-applications-performance-for-expensify) Search screens loaded 4.5× faster, too. We added continuous performance checks to catch regressions. 5x Faster message sending time ### [Agentic delivery: up to 3x estimated acceleration.](https://www.callstack.com/case-studies/building-an-agentic-sdlc-for-a-web-launch-in-under-one-month) Agents executed an estimated 80% of development effort. Engineers owned architecture, review and release. 3x Delivery acceleration · 70 Pages in 3 weeks · 80% Effort executed by agents ### [Let agents verify the apps they build.](https://agent-device.dev/) Our open-source tool lets agents inspect, control and verify apps on real devices. 4,900+ GitHub stars. Built on Agent Device. · T3 · Shopify · Tester Army · Agent Device ### [~6x faster screen prototyping with AI.](https://www.callstack.com/case-studies/engineering-ai-loops-for-a-cross-platform-design-system) From about an hour to around 10 minutes for a typical enterprise screen, using a shared design system across web and mobile. ~6x Faster prototyping · 60+ Components mapped with full coverage · Figma · Claude · Server · Tailwind · Tokens · React · Cursor · ESLint ### [Teamworks: mini-app releases in ~10 min.](https://www.callstack.com/case-studies/accelerating-teamworks-mobile-delivery-with-re-pack-and-module-federation) Re.Pack helped seven mini-apps ship independently. Their previous delivery process took 1–2 days for even small updates. 10 min From code change to mini-app release Why Callstack ## Work with React Native Core Contributors with 100+ enterprise clients and open-source libraries downloaded 50M+ times every month. Expensify · Ticketmaster · DirecTV · MLS · PWC · Evernote · AutoZone · MoMo · Dream11 · Rainbow · Futurewei · RIMAC · Hello Fresh · Haaretz · ForaTravel · CelcomDigi · Teamworks · Boats · Questrade · Dialogue Expert engineering ## We help you launch on more platforms, modernize existing apps, and solve performance and native engineering problems. - [Architecture & Performance](https://www.callstack.com/capabilities/architecture-performance) - [Migrations & Upgrades](https://www.callstack.com/capabilities/ai-assisted-migrations) - [Enterprise Infrastructure](https://www.callstack.com/capabilities/self-hosted-ci-cd-infrastructure) - [Feature Development](https://www.callstack.com/capabilities/feature-development) - [End-to-End Product Development](https://www.callstack.com/capabilities/end-to-end-product-development) - [Team Training](https://www.callstack.com/capabilities/team-training) Agentic delivery ## We bring agents into your software lifecycle so your teams can ship more. - [AI SDLC Advisory](https://www.callstack.com/capabilities/ai-sdlc-advisory) - [AI-Driven QA & Testing](https://www.callstack.com/capabilities/ai-driven-qa-testing) - [Custom Agents](https://www.callstack.com/capabilities/custom-agents) - [Custom & Private Models](https://www.callstack.com/capabilities/custom-private-models) - React Foundation Founding Member · 300+ commits to React Native · Contributing since 2016 - 100+ Enterprise projects delivered - Industry runs on our tooling · 50M+ OSS downloads / month - [3.7× Lower task cost vs Opus 5.5](https://apex.callstack.com) - “I recommend them as a trusted tech partner for running complex projects.” — Jin Chung, Co-Founder, CTO / Rainbow · “Their engineers proved to be a crucial part of our mobile app relaunch project.” — Brian Aznar, Engineering Director / Major League Soccer · “I appreciate their attention to detail, flexible approach and a high degree of expertise.” — Glen Moriarty, Founder and CEO / 7 Cups · “The team at Callstack are the most experienced engineers in the React Native community.” — Nader Dabit, Senior Developer Advocate / AWS · “Their ability to deliver, and follow through, is unparalleled in the React Native ecosystem.” — Matt Hargett, Principal Software Engineer / Roblox - [5x Faster message sending time](https://www.callstack.com/case-studies/enhancing-applications-performance-for-expensify) - ISO 27001 certified Case studies ## What shipping at AI speed looks like. ### [Enhancing Expensify app performance](https://www.callstack.com/case-studies/enhancing-applications-performance-for-expensify) Expert Engineering · Finance **5x** faster message sending time ### [Migrating Questrade Edge Mobile to a Faster, More Scalable Architecture](https://www.callstack.com/case-studies/migrating-questrade-edge-mobile-to-a-faster-more-scalable-architecture) Expert Engineering · Finance **33%** fewer re-renders across most features ### [Teamworks cut mobile change lead time from days to minutes](https://www.callstack.com/case-studies/accelerating-teamworks-mobile-delivery-with-re-pack-and-module-federation) Expert Engineering · Sports & Entertainment **10** min from code change to mini-app release ### [Building an Agentic SDLC for a Web Launch in Under One Month](https://www.callstack.com/case-studies/building-an-agentic-sdlc-for-a-web-launch-in-under-one-month) Agentic Delivery · Software Development **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](https://www.callstack.com/contact) Insights ## Worth your time, by engineers. - [React Native Wrapped 2025: A Month-by-Month Recap of The Year](https://www.callstack.com/blog/react-native-wrapped-2025-a-month-by-month-recap-of-the-year) (Article, 10/16/2026): 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. - [Efficient On-Device LLMs in React Native Done Right](https://www.callstack.com/events/efficient-on-device-llms-in-react-native-done-right) (Event, 11/17/2026) - [MCP and Supervisor Agents in eBay's Monitoring Workflow With Leonel Candido da Silva](https://www.callstack.com/podcasts/mcp-and-supervisor-agents-in-ebays-monitoring-workflow-with-leonel-candido-da-silva) (Podcast, 10/13/2026) - [Behavior Review for AI-Native Delivery](https://www.callstack.com/events/behavior-review-for-ai-native-delivery) (Webinar, 7/21/2026) - [Your AI Coding Agent Still Needs an Architecture](https://www.callstack.com/blog/your-ai-coding-agent-still-needs-an-architecture) (Article, 10/22/2026) [Explore Insights](https://www.callstack.com/insights)