In the aftermath of the 2008 global financial crisis, housing and tenant movements across many cities have emerged to contest the unfolding cycle of housing financialisation. In particular, tenant organising against corporate landlords has marked the dawn of a new urban politics of space. This article reflects on the political antagonism that the Sindicat de Llogateres (Tenants’ Union of Barcelona) has deployed against corporate landlords using the class composition analysis developed by the Italian-Marxist school of operaismo. I contend that compositional analysis offers a political understanding of the shifting dynamics of rentier capital (technical composition) and the emergence of new forms of tenant contestation (political composition). In Barcelona’s post-crisis urban laboratory, I argue that the concentration of properties in the hands of landowning corporations has shaped new organisational forms of tenant contention, introducing tactical innovations to the established repertoire of housing contention.