Abstract The Behavioral Intervention Development Core will develop innovative and scalable behavioral interventions to improve healthcare delivery for aging adults. The Core will focus on systematic testing of mechanisms of behavior change that drive intervention effectiveness. Following the NIH Stage Model for Behavioral Interventions, the Core will carry out a series of 10 clinical trials. To ensure impactful research, the program has established a network of six diverse health systems that support research on value-based care. The External Advisory Committee, comprised of executives from these systems, along with scientific and methodological experts, plays an integral role in informing the Center's funding priorities and ensuring the translation of behavioral mechanisms into real-world applications. In the first year, two randomized trials will be conducted to address barriers to the adoption of value-based practices and explore associated mechanisms of behavior change. The first study involves adapting a multifaceted medication safety intervention that showed mixed results in a Stage IV replication of a successful Stage III trial. This intervention will be modified to incorporate recent findings from behavioral science and will test whether the identity of the messenger moderates the effect of behavior change. The second trial aims to promote patient uptake of a healthcare proxy and examines the mediating role of planning prompts. The specific aims of the trials are as follows: Aim 1 will establish an infrastructure for developing and testing potent, scalable interventions that advance scientific mechanisms of behavior change and employ the NIH Stage Model. This includes maintaining and extending our network of implementation partners, updating requests for applications and scoring based on scientific evidence and implementation priorities, and providing support to awardees throughout the research and intervention development process. Aim 2 will adapt and test a multifaceted medication safety intervention in a Stage III cluster randomized trial, comparing the effectiveness of different forms of scalable feedback on the overuse of potentially inappropriate medications. Hypotheses will explore the reduction of medication prescribing through automated feedback messages based on aspirational social norms and the moderating effect of different types of messengers. Aim 3 will conduct a Stage III randomized trial to assess the efficacy of encouraging patients, prior to primary care provider appointments, to complete the health care proxy portion of an advanced directive, with or without a planning prompt. Hypotheses will examine the impact of an easy-to-use health care proxy form and the additional effect of a planning prompt on increasing health care proxy designation. The Core's ultimate goal is to advance the behavioral science of value-based care and improve the health and well-being of aging populations.