The performativity of economics programme, pioneered by actor-network theorist Michel Callon, has emerged as an important theoretical intervention at the intersections of science studies, economic sociology and the anthropology of valuation. Exploring the case of contested carbon market designs in global climate governance, however, this article argues that performativity analysts have so far failed to pay sufficient attention to the political dimensions of marketization. Adopting insights from recent materialist approaches to the politics of techno-science, the article addresses this imbalance by outlining three modalities of techno-economic citizenship, as these interfere with the shaping of specific carbon market designs. Drawing on web-based research tools and document analysis, each modality is illustrated via transnational environmental NGO practices of contestation, particularly in the global South. The performativity programme, it is concluded, stands to gain from conceptualizing politics as dynamic assemblages of collective actors, sites of contestation and technologies of witnessing. Re-framing performativity in this direction allows for a reintegration of economics into a wider political ecology of contested eco-sciences.