| We propose an interactional generalisation of structured exceptions based on the session type discipline. Interactional exceptions allow communicating peers to asynchronously and collaboratively escape from the middle of a dialogue to reach another in a coordinated fashion, under an arbitrary nesting of exceptions. New exception types guarantee communication safety, as well as offering precise representations and type-abstraction of advanced conversation patterns found in practice. Protocols for coordinating normal and exceptional exit among asynchronously running sessions are introduced. The liveness property established under these protocols guarantees consistency of coordinated exception handling among communicating peers. |