Urban areas are complex and dynamic systems that connect human, environmental, and technical systems across different scales and sectors. Decision-making surrounding the management of such complex systems, particularly under climate change, requires a plurality of knowledge that incorporates multiple perspectives and ways of knowing. However there remain persistent gaps in current complex systems research; for example, such research processes often do not include the knowledge of relevant decision-makers and communities and/or multiple perspectives across sectors and disciplines. Therefore the knowledge generated from current research is not often not actionable for decision-making. Coproduction processes that bring together diverse knowledge holders with decision-maker and user communities, to collaboratively design and undertake research, has been shown to be an effective way to generate actionable knowledge for complex urban systems. Here, we present learnings from a long-term co-production project (6+years) that brings together scientists from various disciplines with energy, water, and land managers to co-develop actionable climate science. Through a longitudinal analysis, we trace how the science evolved over time, and identify the different ways in which the iterative engagements with sectoral decision-makers changed the scientific questions, approaches and outputs. We specifically highlight examples on how the co-production approach helped to improve the decision-relevance of a climate-water-energy nexus modeling effort.