Background: Gastrointestinal cancers present complex clinical challenges, placing substantial burden on patients, caregivers, and the healthcare system. Major surgery remains the primary curative treatment but can be associated with high complication rates and prolonged hospital admissions. Despite evidence supporting (p)rehabilitation, accessibility remains a major barrier. AI-driven, avatar-based interventions offer a scalable solution by delivering personalised support at the point of care, bridging the gap between specialist care and recovery at home. This study aims to co-design and evaluate PRIORITY-CONNECT SMS; an AI-driven, avatar-based video message intervention that provides semi-personalised, evidence-based, pre- and post-surgical support for patients undergoing gastrointestinal cancer surgery. Methods: Using a sequential, exploratory, mixed-methods design, the study will engage patients, caregivers, clinicians, and researchers across two stages. Stage 1 will involve interactive focus groups with patients and caregivers to identify appropriate supportive care interventions and explore preferences for the content, timing, and delivery of supportive messages throughout the surgical treatment pathway. Insights will inform the development of video message scripts, with clinical guidelines and behaviour change principles integrated throughout. Patient and caregiver feedback will refine the scripts before conversion into avatar-based video messages. Stage 2 will evaluate the videos’ clarity, engagement, and appropriateness, through surveys and interviews, with iterative refinements based on user feedback. Discussion: This study outlines a rigorous process for developing and refining the PRIORITY-CONNECT SMS intervention, an innovative approach designed to improve perioperative support for patients with gastrointestinal cancer and reduce the strain on the healthcare system.