Arenas where experts interact with publics are useful platforms for communication and interaction between actors in the field of public health: researchers, practitioners, clinicians, patients, and laypersons. Such coalitions are central to the analysis of knowledge coproduction. This study investigates an initiative for assembling expert and other significant knowledge which seeks to create better interventions and solutions to addiction-related problems, in this case codependency. But what and whose knowledge is communicated, and how? The study explores how processes of repetition, claim-coupling, and enthusiasm produce a community based on three boundary beliefs: (1) victimized codependent children failed by an impaired society; (2) the power of daring and sharing; and (3) the (brain) disease model as the scientific representative and explanation for (co)dependence. These processes have legitimized future hopes in certain suffering actors, certain lived and professional expertise and also excluded social scientific critique, existing interventions, and alternative accounts.