The consumption of cobalt has tripled globally over the last decade, largely driven by rising demand for electronics and electric-battery vehicles. This fast-growing market has pressured multinational mining companies operating in the Democratic Republic of Congo, the world's largest supplier of cobalt, to formalize artisanal mining under the banner of responsible sourcing. Based on field research in the cobalt-rich Province of Lualaba, survey data and interviews with relevant actors, this article examines the integration of artisanal miners in corporate-led formalization projects. First, we suggest that the reliance on wageless artisanal workers in large-scale industrial operations holds important lessons for understanding the unintended effects of mining formalization. Second, the flexible recruitment of artisanal workers by mining companies represents an emergent trend of corporate outsourcing of responsibility.