Adolescent Idiopathic Scoliosis (AIS) is a prevalent global health challenge. While mild to moderate cases comprise 90% of AIS patients, products and services tailored to these populations remain largely underdeveloped. Exercise-based interventions have emerged as the preferred rehabilitation approach for mild to moderate cases. Yet, a substantial disconnect persists between theoretical service frameworks and the practical implementation of exercise rehabilitation. Technologies like AI and smart wearables have been applied successfully to improve the efficiency and experience of healthcare. This study presents a concept design of smart product-service systems (Smart PSSs) for AIS exercise intervention supported by AI agents. Through a double-diamond research process, three design insights were defined: improving service navigation, enhancing adolescent engagement, and strengthening companionship feedback. A Smart PSS framework was proposed, incorporating digital touchpoints and smart wearables. A comprehensive set of AI agent tasks demonstrates the data flow of how the AI agent processes and provides feedback based on information from patients, therapists, and local contexts. These tasks show how AI agent integration enhances exercise rehabilitation service effectiveness by enabling continuous support through cross-scenario data integration. Finally, seven service scenarios were further designed and iterated through user testing. This research contributes to AI-enabled exercise rehabilitation from a design perspective while providing data-driven insights for applying AI capabilities in exercise rehabilitation services.