Challenge-led interdisciplinary research is a relatively new way of bringing together disciplinary expertise in response to complex societal and environmental problems. Common difficulties include how to define 'interdisciplinary research'; how to improve the participation and flourishing of early-career researchers; and how to manage projects with disparate teams of researchers while deepening external collaborations. This article reports from a major initiative of this type. It interrogates qualitative data generated from program evaluation among participating researchers, identifying insights on beneficial structural (program design) and 'soft' infrastructure (human capital) variables, as well as on-going barriers and tensions. Notwithstanding the difficulties of communicating and collaborating across epistemic domains, the program in question exceeded expectations in building interdisciplinary research and early research careers--though not necessarily in ways initially imagined. Staggered funding pools meant it was acceptable in early phases for low-cost projects to 'fail safely', while strict funding guidelines on distal interdisciplinarity compelled unlikely and novel researcher combinations and projects. Moreover, such program design features 'granted permission' to early-career researchers to approach more senior, cross-faculty researchers as potential collaborators, hence building leadership capacity. Human capital variables included a dialogic approach to project development ('curating' projects as they evolve), inclusive program leadership, and promotion of the benefits of a collaborative rather than competitive research culture. Distal interdisciplinarity not only nourishes novel and unlikely research projects that respond to complex problems; with good program design and meaningful relationships it can, we argue, also build research careers differently from an early phase.