Co-production is increasingly recognised as central to improving the quality, relevance and ethical integrity of mental health science, yet evidence is still needed on how lived experience involvement can be meaningfully embedded and sustained in complex research settings. Global Alliance for Living Evidence on Anxiety, Depression and Psychosis (GALENOS) is a Wellcome-funded collaboration conducting living systematic reviews and evidence triangulation, with people with lived experience contributing as Experiential Advisors and through a Global Lived Experience Advisory Board. This perspective uses GALENOS as a case example to reflect on what meaningful co-production practically requires especially in the context of large-scale, technical and international collaborations. It draws on a collective reflection designed and led by people with lived experience, developed through workshops and written contributions involving lived experience contributors, researchers and project-support staff. Discussions were organised around lived experience involvement, capacity development, diversity and representation and influence in strategic decision-making. Across these areas, contributors identified that experiential knowledge needs to become consequential, participation must be supported through care and flexibility, diversity must shape interpretation rather than representation alone and influence must be embedded in governance and decision-making. GALENOS shows that co-production is not a fixed method but an evolving relational practice requiring practical infrastructures for accessibility, accountability, continuity and ethical care.