Engineers from Square have presented about the Workflow framework at Droidcon 4 different times before. Over the past 4 years we have continued to evolve and improve the library, including some API changes. The usage continues to grow, making up over 70% of Square Android application screens but over those 4 years we ended up with 4 different versions of Workflow in use in the codebase at the same time. In this talk we’ll tell you a story of consolidating the API over the huge megarepo, and a migration of more than 500 screens to a single version of the framework. Learning Points: - How one can use code static analysis tools such as ktlint to aid in an API migration that is not possible as entirely mechanical (i.e. without engineer critical thinking). - The importance of quick, visible feedback to migration efforts. - The value of ease-of-use and satisfaction for developers with migration tools.