This paper introduces Hypersequent GV (HGV), a modular and extensible core calculus for functional programming with session types that enjoys deadlock freedom, confluence, and strong normalisation. HGV exploits hyper-environments, which are collections of type environments, to ensure that structural congruence is type preserving. As a consequence we obtain an operational correspondence between HGV and HCP -- a process calculus based on hypersequents and in a propositions-as-types correspondence with classical linear logic (CLL). Our translations from HGV to HCP and vice-versa both preserve and reflect reduction. HGV scales smoothly to support Girard's Mix rule, a crucial ingredient for channel forwarding and exceptions.

@article{paperbot2207,
  title = {Separating Sessions Smoothly},
  author = {Simon Fowler and Wen Kokke and Ornela Dardha and Sam Lindley and J. Garrett Morris},
  journal = {Logical Methods in Computer Science},
  volume = {Volume 19, Issue 3},
  year = {2023},
  doi = {10.46298/lmcs-19(3:3)2023}
}