Summary Tobacco use remains the leading preventable cause of death in the US, contributing to more than 480,000 premature deaths each year. The well-established Tobacco Treatment Guidelines and recently released American College of Cardiology Expert Consensus Decision Pathway for tobacco cessation treatment underscore the need to conceptualize tobacco use as a chronic substance use disorder and to offer any patients who use tobacco products brief interventions that include prescriptions for proven pharmacological smoking cessation aids and proactive connections to evidence-based behavioral support. The rapid expansion of smart phone capabilities enhances the potential for tobacco cessation apps to personalize behavior change guidance and to send contextually relevant tailored behavior change nudges based not just on readiness to quit, but also based on electronic heath record (EHR) data. Rich data from EHRs are now available to third-party apps from the Health app (iOS) via Fast Healthcare Interoperability Resources (FHIR) standard Application Programming Interface (API). The proposed research represents an innovative approach in that it will develop and examine the feasibility, acceptability, and preliminary effects of FHIR-ed Up- a theoretically-grounded, highly individualized tobacco cessation Health-Kit enabled app. Unlike existing tobacco cessation apps, FHIR- ed Up will: 1) implement a full range of best practices in tailored health behavior change communications; 2) individualize messaging based on Health app data and behavior change constructs; and 3) provide data and key insights back to electronic health records via HL7 transmissions from the server-portion of the FHIR-ed Up app. Developed in collaboration with interoperability and app development experts, FHIR-ed Up will achieve sustained use by hyper-personalizing the user experience for patients and integrating actionable insights seamlessly into the clinical workflow of their clinicians. Extensive end user and stakeholder input will ensure FHIR-ed Up is designed for rapid dissemination. Potential end users (n=8 tobacco users aged 18 and older) will be recruited via community and social media ads. Formative qualitative data will be combined with input from four experts and five clinician stakeholders to develop a prototype of FHIR-ed Up. Iterative usability testing (n=10) will allow the prototype to be refined before patients of an integrated delivery system with an upcoming appointment (n=100) are recruited to participate in a 30-day pilot test. Pilot participants will provide quantitative and qualitative data, and utilization and acceptability data will be examined. Pre-post comparisons of psychosocial expectancies for smoking will provide preliminary data on the effects of the program. Acceptability data from participating clinicians (n=5) who receive and deliver EHR prompts will also be gathered. The results will inform program modifications needed to proceed with the Phase II ef...