This paper presents a model of session-based concurrency with constructs for runtime adaptation. Our model allows for the dynamic update of the behavior of communication-centric systems. We propose an event-based approach: adaptation requests, issued by the system or its environment, are assimilated to events which may trigger runtime adaptation routines. Based on type-directed checks, these routines naturally enable the reconfiguration of processes with active sessions. An associated type system ensures communication safety and consistency properties: while the former guarantees absence of runtime communication errors, the latter ensures that update actions do not disrupt established sessions.