(Watch the RECORDING.) The EC-funded DIAMAS Project has done much to develop a more sustainable social, technical, and organisational infrastructure for Diamond OA publishing across Europe—creating a foundation that will endure well into the future. We will share how DIAMAS built a vibrant international Diamond community and developed tools and services that address concrete challenges through strategic co-creation and stakeholder consultation. We will also discuss how the project assumed responsibility for sustaining these efforts longer term through the European Diamond Capacity Hub (EDCH). This session will take you on our 3-year journey of community engagement, culminating in the EDCH: a new hub for the Diamond OA ecosystem in Europe. We’ll show how we convened over 4,000 experts across 60+ DIAMAS-organised events—including hackathons, surveys, webinars & workshops—delivered in multiple languages and regions. By leveraging existing networks and nurturing new ones, DIAMAS helped catalyse the growth of national and regional Diamond Capacity Centres across Europe. Strategic communication with stakeholders—from funders and institutional publishing service providers to policymakers and learned societies—was central to making progress with Diamond OA in Europe. Recommendations and services were designed to be both ambitious and realistic, grounded in a deep understanding of the needs of institutional publishers. Key outcomes—such as the DIAMAS recommendations, the DOAS quality standard, sustainability services, the EDCH registry, and the EDCH forum—have been enriched through broad-based community input and collaboration. The EDCH now carries forward the legacy of DIAMAS. It is a collective initiative aimed at strengthening the European Diamond OA ecosystem by supporting institutional, national, and disciplinary Capacity Centres, along with Diamond OA publishers, service providers, and tech providers. It provides tailored support, training, and networking opportunities for Diamond OA journal editors. Fostering a collaborative community through its registry and forum, the EDCH provides best practices, quality assurance frameworks, and tools that enhance editorial management. This approach reinforces integrity and transparency in scholarly publishing and stimulates a sense of belonging among editors—encouraging peer exchange and mutual support. The transition to Diamond OA is a significant challenge, but one that can be achieved when built by, with, and for the community it serves. We hope this presentation will inspire others to design capacity-building publishing projects with people at the centre from the outset to help meet longer-term goals and OA change management challenges.