Session type systems are an effective tool to prove that communicating programs do not go wrong, ensuring that the participants of a session follow the protocols described by the types. In previous work, we have introduced a typing discipline for the analysis of progress in binary sessions. In this paper, we generalize the approach to multiparty sessions following the conversation type discipline, while strengthening progress to liveness. Conversation types allow to discipline interaction in systems where a possibly unanticipated number of multiple participants interact using a single medium of communication. We combine the usual session-like fidelity analysis with the liveness analysis and devise an original treatment of recursive types allowing us to address challenging configurations that are out of the reach of existing approaches.
