Capstone software engineering courses provide students with real-world team project experience, but ensuring effective and equitable collaboration remains challenging. In this study, we explored the impact of incorporating activities into the assessment structure of a large undergraduate capstone course on students’ teamwork experiences. In 2024, agile practices, such as daily stand-up meetings, sprint retrospectives, and collaborative planning sessions, were integrated into the grading system, partly to address collaboration issues and partly to respond to increased use of Generative AI tools like ChatGPT. We analyzed data from 872 student surveys across four course offerings from 2022 to 2025, together with 12 semi-structured interviews. Our results indicate that the agile practices supported accountability, reflection, and participation by making collaboration more visible and harder to postpone. We discuss implications for collaboration-focused assessment in capstone courses and provide an overview of the team activities incorporated in the course.