Developed a passwordless authentication feature for the aws-amplify/amplify-flutter repository, enabling users to sign in via SMS OTP and streamlining the onboarding process. The work involved implementing end-to-end support for SMS OTP challenges within the USER_AUTH flow, including updates to state machines, mappings, and constants to recognize and process the new challenge type. Using Dart and focusing on mobile development and authentication, the changes addressed a previously unhandled state, improved sign-in reliability, and reduced user friction. This enhancement aligned with the project’s roadmap to simplify authentication for Flutter clients, ultimately decreasing support inquiries related to onboarding and sign-in.