This paper describes Livingstone, an implemented kernel for a self-reconfiguring autonomous system, that is reactive and uses component-basedeclarative models. The paper presents a formal characterization of the representation formalism used in Livingstone, and reports on our experience with the implementation in a variety of domains. Livingstone’s representation formalism achieves broad coverage of hybrid software/hardware systems by coupling the concurrent transition system models underlying concurrent reactive languages with the discrete qualitative representations developed in model-based reasoning. We achieve a reactive system that performs significant deductions in the sense/response loop by drawing on our past experience at building fast propositional conflictbased algorithms for model-based diagnosis, and by framing a model-based configuration manager as a propositional, conflict-based feedback controller that generates focussed, optimal responses. Livingstone automates all these tasks using a single model and a single core deductive engine, thus making significant progress towards achieving a central goal of modelbased reasoning. Livingstone, together with the ttSTS planning and scheduling engine and the I~APS executive, has been selected as the core autonomy architecture for Deep Space One, the first spacecraft for NASA’s New Millenium program.