This article seeks to problematize and develop the concept of resilience in social security systems by focusing on more endogenous processes – specifically, endogenous welfare austerity. Existing literature on both resilience and welfare austerity has predominantly focused on external factors orformal institutions as the primary sources to change. However, Sweden offers a compelling case that challenges this assumption. Over an extended number of years, reaching its peak at the end of the last decade, the Swedish Social Insurance System (SSIS) has become increasingly restrictive, despite the absence of corresponding changes in the law or through reforms. Rather than exogenous pressures, we argue that the roots of welfare austerity in Sweden lie within an informal institution: the SSIS knowledge regime. Drawing on Michael Walzer’s “sphere-approach” from 1983, the article highlights the character of the knowledge regime – plural or authoritative– as a useful theoretical framework for understanding endogenous austerity. We contend that the SSIS knowledge regime, composed of distinct spheres, each governed by its own norms and logics, has in recent years been annexed by the welfare bureaucracy. We identify two forms of bureaucratic annexation: the supplanting and incorporating of other spheres of knowledge. The article demonstrates that, if social security systems are to be able to respond resiliently to external fragile situations and extreme events, it is crucial to develop a deeper understanding of their internal, more subtle vulnerabilities.