This report outlines the DIAMOND project’s strategy for developing structured, meaningful synergies with other research initiatives—particularly its Horizon Europe sister projects—to maximise scientific impact, enhance cooperation, and strengthen the relevance of climate-policy modelling. Building on the project’s core vision of openness, interdisciplinarity, and co-creation, the report establishes how collaboration with aligned projects can support the project’s ambition to advance next-generation integrated assessment modelling (IAM) and to contribute robustly to European and global climate policy processes. Expanding on the plan, we highlight the synergies established so far, which include 35 joint scientific publications, 33 joint conference presentations, the organisation of two webinars with contributions from other projects, the co-organisation of two side events at COP28 and COP30, and active participation in the MAIA project’s activities and Climate Research Communication Network.