The Shim Proxy Pattern: A Zero-Disruption Path from React Native Legacy to Expo CNG

Preface Over the years as a React Native developer, I've run into the same problem more times than I'd like to admit — migrating legacy projects to newer versions and dealing with the endless headaches that come with it. I've even resorted to what people quietly recommend in the depths of internet forums: copying files to a new project one by one until everything works. It sounds ridiculous, and it is, but sometimes it's the only realistic option. The problem is it doesn't scale — you can't pull that off in a large team with tight delivery cycles. Today I'm sharing an architecture I designed to attack exactly that: migrating a React Native CLI project to Expo without stopping the development cycle or executing a massive refactoring effort. The Problem Older versions of React Native handed you complete control over the native layer. At the time, that made sense — the ecosystem was young, Expo wasn't production-ready, and if you needed something custom you had to go deep into Xcode and G