The creation of Frontex responded to the quest for enhanced integration of national border services within the framework of Schengen cooperation at the external borders. Its empowerment as the institutional actor in charge of the development of the EU Integrated Border Management (ibm) granted much more than that. There are at least two efficiency spill-overs that are tightly linked to Frontex-coordinated border management: (a) the crafting of the EU’s external borders as a unified “border zone”, administrated by means of enhanced inter-agency and international cooperation; (b) the externalisation of EU’s responsibilities for internal security and fundamental rights protection, by means of atypical cooperative tools, characterised by an elevate degree of legal hybridism. This chapter seeks to advance the understanding of the “foreign affairs-migration policy nexus”, taking as a case study the gradual establishment of an integrated management system for EU’s external borders. It investigates Frontex’ contribution to the development of the EU’s external borders as “smart borders” ruled by a new typology of anticipatory border governance. Then, it explores the balance that Frontex’ last reform strikes between the search for efficiency spill-overs within the “brand-new” European ibm and the adherence to “old-fashioned” legal principles, steering the afsj. In doing so, it explains how and why the agency option has fostered the metamorphosis of a process of integration of Schengen States’ border control services into a process of intersection of policy goals, belonging to different policy universes.