Contracts, not conventions: keeping one promise across Android, iOS, Flutter and React Native

Shipping the same product on several platforms comes with a promise: it will behave the same everywhere. Smile ID ships identity verification as four SDKs, for Android, iOS, Flutter and React Native, in four languages, and partners expect one experience from all of them. This session is the playbook we use to keep that promise, and it applies to any team maintaining one product across several stacks. Keep the public surface small and identical, so you can change how things work inside without partners touching their code. Build the hard parts, such as the camera and the screen flow, once per platform and share them, instead of borrowing a different plugin for each framework. Write the rules that must match as data your builds check, not as conventions people remember. Keep a record of the differences you keep on purpose. Test and release every platform in step. You'll leave with a checklist you can apply, whatever your stack.