Migrating Shop app from React Native to native

Summary

Shop migrated its React Native app to native iOS and Android implementations in SwiftUI and Jetpack Compose after coding-agent advances changed the economics of a shared mobile codebase. A one-week proof of concept showed that one engineer using agents could recreate screens, interactions, and flows closely enough to make a full migration feasible although the result was not production-ready. Six engineers then built the native foundations and main journeys with feature teams validating edge cases; they preserved sign-in state, push notifications, analytics events, and behavior while simplifying some screens. Compared with React Native, native startup was 23% faster on iOS and 50% on Android, stability rose from 99.5%+ to 99.95%+, Android size dropped 109 MB, release builds fell about 75%, and scrolling reached 120 FPS. The migration’s workflow combined specialized agents, plan approval, Tardis live-app feedback, screenshot and event comparisons, and human review while feature parity remained a release requirement.

Takeaways

1. 1

   A one-week proof of concept, led by one engineer using coding agents, recreated enough of the existing React Native app’s screens, interactions, and flows to support a full migration.

2. 2

   Native releases improved several measured outcomes: iOS and Android startup was 23% and 50% faster, Android size fell by 109 MB, Android release builds took about 75% less time, and scrolling reached 120 FPS.

3. 3

   Tardis gave agents structured access to native app events, logs, and state, while checkpoint comparisons checked event names, counts, payload fields, and relationships across React Native and native flows.