Interactive oral assessment (IOA) takes the form of a professional conversation between a student and their educator. It shows great promise as a rare mode of secure assessment that can be authentic and engaging for students if thoughtfully designed (Ward et al., 2024). This paper reports on a case study that is part of a wider investigation into the experience of developing, delivering and engaging in IOAs for both students and educators. In this case, we report on the effects of using genAI assistance for students in preparing for IOAs in a postgraduate business course. The course has been run three times with an IOA as the final assessment. In the first two instances, evaluation of the assessment experience revealed that students had been using genAI in different ways to augment the existing support provided by the educator to prepare for the IOA. In the third delivery of the course, students were provided with a customised chatbot, co-designed with previous students in the course, as part of their support for the assessment. Data collected under ethics were: aggregated assessment data for all three deliveries, student focus group interviews for all three deliveries, chatbot conversation histories for the third delivery and interviews with the educator for the first and third delivery. Evaluation in the wider project had shown that the student experience of IOAs mapped closely to Earl and Timperley’s professional conversation framework (Earl & Timperley, 2009). This framework is used to abductively thematically analyse the student interviews and the chatbot conversations to identify how the chatbot fit into the support students made use of in preparing for the assessment, and how it affected their use of other support mechanisms in order to better tailor the design of the IOA experience.