Biometric login on React Native with Keychain

Adding Face ID and Touch ID to a React Native app sounds like a single API call. It isn't. There are three pieces you have to wire together: Keychain for storage, the biometric prompt for the user gate, and your auth code for what to do with the result. react-native-keychain handles the first two well. This post is about wiring all three. I'll walk through the mental model, a storage pattern that's served me well, the configuration flags that matter, and how to deal with the prompt errors you'll