Migrations & Upgrades

Execute complex migrations fast and with confidence.

We move your product off legacy systems onto a stronger, more secure foundation. Expert engineers and AI-assisted workflows help you execute complex migrations faster and with confidence.

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Trusted by 100+ Enterprise clients

Why migrate with Callstack

Put expert engineers in charge of your migration.

We lead your migration from codebase assessment to rollout. Agents accelerate repetitive changes while our engineers handle architecture, compatibility, and native integrations.

  • Move off legacy faster.

    Replace architectures that slow delivery and make change harder.

  • Choose the right migration path.

    Rebuild or migrate incrementally, balancing speed, cost, and risk.

  • Reduce migration risk.

    AI-native workflows improve planning, validation, and execution without giving up engineering control.

  • Build faster after migration.

    A stronger foundation makes future delivery easier, faster, and cheaper.

Services

Move to the stack that fits next.

  • Technology Migrations

  • Migration to React Native

    Move iOS and Android apps off separate native codebases onto one cross-platform stack, with the same product shipping to both stores from one codebase.

  • Migration to Self-Hosted Infrastructure

    Move builds, CI/CD, and delivery off hosted platforms onto hardware you own, with full control over cost, security, and operations.

  • Migration to Modular Architecture

    Break a monolithic app into independently deployed mini-apps that let engineering teams ship in parallel.

  • Migration to Expo

    Move to Expo's managed workflow and EAS infrastructure. Faster builds, simpler releases, and full access to the modern React Native ecosystem.

  • Migration to Next.js

    Move legacy React or SPA apps onto Next.js, adding server rendering, streaming, and edge delivery to the React stack.

  • React Native Modernization

  • Migration to New Architecture

    Move React Native apps to the New Architecture (Fabric, TurboModules, and JSI), unlocking faster UI and synchronous native calls.

  • React Native Upgrades

    Upgrade to the latest React Native release, patching security vulnerabilities and bringing the app up to date with new features and supported libraries.

  • UX Modernization

    Improve high-impact journeys without rewriting the whole app, using product data, staged rollout, and real-device validation.

  • Tech Debt Reduction

    Refactor legacy code, tightly coupled modules, and deprecated APIs that block upgrades, migrations, and major feature work.

Migrations & Upgrades

Plan your next migration or upgrade.

Send us the current stack and where you want to land. We'll come back with the migration path and the timeline.

Get my migration plan

How we work together

Move from migration plan to rollout.

  • 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

  • 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

  • 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
Industry runs on our tooling
50M+
OSS downloads / month
4x
More React Native pages
30%
React Native adoption
60 → 10min
Faster builds after replacing Jenkins with EAS
React Native Brownfield

Tooling for introducing React Native into existing native apps incrementally.

100+
Enterprise projects delivered

10 years of React Native → Now in your AI stack

Plan your next migration or upgrade.

Send us the current stack and where you want to land. We'll come back with the migration path and the timeline.

Get my migration plan

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.

Check All ToolsExplore AI Infrastructure

React Native Brownfield

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

552 stars

Agent Skills

Callstack’s best practices on React Native performance optimization, upgrading, CI workflows, and brownfield migrations

1.7K stars

React Native Community CLI

Command line tools to help you build React Native apps

13.5M downloads/mo

React Native Builder Bob

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

1.4M downloads/mo

Rock

Modular toolkit for teams building React Native apps

700 stars

Re.Pack

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

2.2M downloads/mo

Reassure

Performance testing companion for React and React Native

1.5K stars

Insights

Worth your time, by engineers.

Explore Insights
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Oct 9Talk

React Native Brownfield Deep Dive: How RN Moves Into Native Applications

Artur Morys-Magiera will explain how React Native can move into an existing native app without forcing a big-bang rewrite.

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Oct 8Talk

Same Destination, Different Roads: Migrating a Live App at Scale

Łukasz Chludziński compares Greenfield and Brownfield approaches to migrating a live app, weighing continuity, delivery speed, cost, and risk.

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Aug 27Article

React Native in .NET MAUI: A Practical Brownfield Integration Guide

This article walks through how we embedded React Native inside a .NET MAUI application using a brownfield setup. It covers the packaging layer, lifecycle wiring on iOS and Android, navigation through MAUI Shell, and shared state between the MAUI and React Native runtimes.

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Aug 27Talk

Adoption of Brownfield in React Native

Artur Morys-Magiera will explain how teams can adopt React Native incrementally inside existing native applications.

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Aug 18Meetup

Agentic AI in the Wild - Boston Dev Community Meetup

Join us in Boston on August 18 for an evening focused on a question most teams hit quickly with AI agents: how do you make them dependable once they leave the prototype phase and start touching code, workflows, and delivery timelines?

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Aug 3Article

Migration to React Native in 2026 Starts With a Delivery Question

This article helps mobile teams choose between brownfield and greenfield React Native migration. It explains how each approach shifts risk across continuity, native dependencies, delivery pressure, verification, and architecture ownership, and introduces a checkpoint-based path for teams that want to test a greenfield rebuild before committing. It also shows where AI can help and what still needs human control.

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Jul 8Article

How we made Hybrid iOS apps compile 39% faster with React Native Brownfield

React Native Brownfield 3.10 brings iOS prebuilts into the packaging flow, removing a major compile step from hybrid app builds. This article explains how the integration works, what changed under the hood, and what our benchmark results show for React Native and Expo projects.

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Jun 11Article

AI-Assisted React Native Migration for TV: Lessons From Zattoo

Zattoo started its React Native TV migration before today’s AI-assisted workflows became common. Their story shows where AI can now support similar migrations, from onboarding and refactoring to testing and platform-specific implementation work.