Lesson study's international popularity spread as a unique, agency-oriented model of teacher professional development that is context-rich and deeply rooted in teacher subjectivities. This project aimed to answer the question, what do mathematics teacher education researchers learn about teacher learning by focusing on uncertainties as they arise when the group is trying to construct new knowledge in lesson study? Using ethnographic case study, this article explores the ways one community of practice in a Chilean school negotiated evolving objectives over the course of one school year and how I as the lesson study facilitator took up roles to support collaborative meaning-making and decolonize lesson study as a professional development tool through the use of framing.