ABSTRACT:This formative intervention study explored how four Australian language student teachers engaged with learning with GenAI. This intervention provided structured tasks for fostering their agency, including prompt revision, evaluating GenAI’s outputs, and reflective discussion on GenAI implications. The analysis of their interaction with GenAI and group discussion showed that student teachers quickly learned to use various GenAI tools, and then took agency and critically reflected on the broad implications of GenAI and ethical considerations. These findings suggest that although there are concerns about GenAI, formative intervention can empower them to be agentive and critically integrate GenAI with professional knowledge.Keywords: Generative AI, language teacher education, formative intervention, transformative agency, knowledge integration