Adolescence is a challenging period for individuals with autism because they undergo radical physical, emotional, and social transitions. We describe our setup to support the self-management of adolescents with autism for assisting adaptive transitions. We propose COSMA, an interactive mobile application that allows both individuals with autism and their caregivers to cooperatively manage, plan, reflect on, and improve behavior. COSMA is a self-management tool for adolescents with autism, including behavioral goal setting by means of the co-contract process, self-reporting while performing everyday tasks, and cooperative reflection to support their smooth transition to adulthood.