The present paper proposes a hybrid approach based on reactive agent technology as a post-object paradigm for building intelligent CAD systems. It represents an evolution of previous positions and articles by the authors motivated by a clear need to provide forms of active support for the design process rather than seeking full design automation purposes. Key concepts about agency and reactivity, as well as their usefulness in design systems, are presented. Also a basic tool called XLOG+, for developing agent-based systems, comprising logic and object oriented approaches, is discussed. Finally, the proposed hybrid agents are embedded in a new integrated CAD system architecture and an implemented prototype example in the area of solid modelling is briefly presented.