VIRTUOUS PACT is an interdisciplinary project that aims to transform physical activity (PA) support for children, adolescents, and young adults (CAYA) with cancer through the development of an intelligent, adaptive digital therapeutic. While PA is increasingly recognized as a non-pharmacological therapy in oncology, most programs remain inaccessible, unpersonalized, and impractical— particularly for young patients facing hospitalization, fatigue, or mobility limitations. The project addresses major clinical and behavioral barriers by creating a virtual reality (VR) and AI-powered companion that delivers personalized PA sessions throughout the care continuum—from hospital to home. Unlike traditional video games or coaching apps, this system integrates real-time physiological, emotional, and behavioral data to dynamically tailor exercise content and intensity. It also acts as an emotional and social support, reducing isolation and fostering long-term engagement. Key actions include the development of adaptive VR and mobile interfaces, a wearable monitoring system, and a clinical trial to validate safety and efficacy. A longitudinal multi-omics study will explore the biological impact of personalized PA, laying the foundation for precision exercise oncology. VIRTUOUS PACT unites six European partners with expertise in oncology, sports science, gamification, AI, and digital health. The team’s diversity ensures clinical relevance and technical innovation. In the long term, VIRTUOUS PACT will establish a new category of digital therapeutics, redefining how PA is prescribed and experienced in cancer care. The platform’s adaptability also positions it for broader use across chronic illnesses, contributing to a future of personalized, evidence-based movement therapy.