Just transitions necessitate democratic interfaces where knowledge and action are co-produced by researchers and societal actors. However, the risk of delegitimisation due to being seen as politically involved makes co-production of research with non-academic actors an Augean undertaking for researchers. Co-production efforts have been critiqued for inattention to relational and power dynamics and reproduction of simplistic linear models of connecting knowledge to action – ‘speaking truth to power’. Such critique necessitates nuancing the understandings of co-production and the relationship of truth and power it generates. To this end, this paper investigates how two understandings of co-production, as a collaborative process and a sociopolitical phenomenon, are connected in praxis through a layer of normative ideals and theories of societal change held by researchers and societal actors. This connection is explored through the analysis of two knowledge-action interfaces: the climate citizens’ assembly and the training programme for trade union executives run by a Swedish policy-relevant research programme. The two interfaces explicate the complexity of knowledge politics aimed at democratically embedding scientific research in a political conjuncture which is not conducive to ambitious climate policy. The challenges facing the researchers are the clashing ideas of justice, sectoral and political heterogeneity of trade unions, polarisation, and climate backlash. They try to overcome these through designing processes where the ideas of truth are complexly connected to various forms of power: speaking truth as, with, and through power. The paper opens the black box of co-production, showing how research shapes and is shaped by norms, values, and theories of societal change of the different actors involved in the process, and how co-production is structured and legitimised in response to its sociopolitical context.