Traditional health and fitness journeys are often fragmented and lack personalized guidance, leaving individuals to connect the dots themselves. To address this, a new AI-powered personal health coach is being introduced to provide proactive, personalized, and adaptive health insights and coaching. This innovative coach leverages advances in Gemini models and an AI-first approach within the Fitbit app. It offers personalized guidance based on behavioral science, health principles, and individual metrics like activity and physiological data. The coach also sets goals and builds sustainable habits through adaptive, actionable plans. A public preview for eligible Fitbit Premium Android users in the US is launching, with iOS expansion to follow. Users will need to opt-in and consent to data access for personalized insights. The technology behind the coach involves sophisticated numerical reasoning on time-series data, a multi-agent framework for coordinated support, and careful steering of foundational models for health contexts. Expert validation and iterative user design are crucial for reliability and safety, involving health advisors, fitness professionals, and extensive user feedback. A rigorous SHARP evaluation framework, involving millions of human annotations and evaluations, ensures the coach is safe, helpful, accurate, relevant, and personalized. Users are encouraged to join the public preview and share feedback to help shape the future of this health coach.