This article examines arch-tivism, a mode of architectural practice that fuses spatial co-production with social activism, through three community-initiated Safety Shelters built with residents, safety patrollers and artisans in Stjwetla, Alexandra, as part of the Kelvin–Alexandra–Frankenwald City Studio at the University of the Witwatersrand. Positioning arch-tivism within a longer genealogy of architectural activism – from Weimar-era expressionists, through post-war participatory design, to the anti-apartheid architects of the 1980s – the article argues that the term, despite its rare use, names ideas long present in South African practice. Drawing on situated research and Latour's notion of the matter of concern, it traces how the shelters emerged from mutual knowledge shared between patrollers, artisans, students and researchers, and from the reuse of salvaged materials. The shelters, built outside formal planning frameworks and since appropriated for trading and gathering, are read as micro-infrastructures of care that destabilise, without resolving, the structural inequalities of the post-apartheid city. The article contributes a South African case to international debates on spatial agency and public-interest design, while questioning whether “arch-tivism” is the most apt name for a practice that privileges collective agency over architectural authorship.