This special issue identifies new directions in research on the consequences of international involvement in security sector reform (SSR). Both empirically and theoretically, the focus lies on the so far neglected role of local agency and domestic power constellations. The introductory article maps out different ways to analyse the external-domestic interaction dynamics that structure the often contentious and asymmetric encounters between international and local interests and demands in SSR processes. It makes the case for moving beyond a state-centric approach to the study of security governance in areas of limited statehood and for engaging more closely with the layered, mixed or hybrid security orders that can result from external engagement in domestic reform contexts.