Fig. 1. System setup of the proposed system. The system runs the user-capturing toolkits, behavior generation model, Greta, and SST evaluation. Interlocutors adapt their verbal and nonverbal behaviors as signs of engagement during face-to-face interaction. We aim to build engaging Socially Interactive Agents, SIAs, that can adapt their behaviors during interaction. With an adaptive behavior generation model, we drive SIAs' upper face and head movements in real-time. We evaluate this platform through a scenario for Social Skills Training, SST. CCS Concepts: • Human-centered computing → Interactive systems and tools; • Computer systems organization → Real-time system architecture.