The worst kind of bug is the one that works on your machine, works in the simulator, works on a real device over the dev server, and then dies the moment it hits a production build. No code changed. Same commit. It just crashes.
That was my last few days. We ship a multi-tenant React Native app built with Expo (one codebase, a handful of pharmacy clients). After upgrading to Expo SDK 53, the iOS build started crashing on launch in TestFlight. Local dev was completely fine. The release build was dead on arrival.
If you've hit this on SDK 53 or later, here's what's going on.
The cause
In SDK 53, the New Architecture is enabled by default. In SDK 52 it was opt-in. So just by upgrading, we silently moved the whole app onto a new rendering and native-module system (Fabric and TurboModules), whether our dependencies were ready for it or not.
