Worked on a key API migration in the oppia-android repository, focusing on transitioning from LegacyProfileId to ProfileId to ensure a safer and more incremental migration path. Applied Kotlin and Android development skills to implement domain-layer migrations across core controllers, introducing boundary conversions to preserve existing UI behavior. Developed a centralized migration utility module and updated Bazel build targets to streamline future migrations. Expanded test coverage extensively across both domain and app layers to validate migration correctness and maintain UI stability. This work reduced user risk during the transition and established a foundation for the eventual deprecation of LegacyProfileId.