Roadmap

Direction, not promises. Two rules govern everything below (README §Security has the long form):

Accidents, not adversaries: new checks earn their place by preventing a plausible mistake (stale state, a typo, a race), not by closing a hypothetical attack from a friend.
Social, not mechanical: new features earn their place by encouraging people to work together in a terminal, not by adding machinery.

Next: small, high value

party knock <name>: an uninvited group member pings the host via write(1): "veg wants to join fiesta". party list already shows invite-only parties; knock completes that loop. The feature most likely to cause spontaneous pairing.
party log: per-party transcript via tmux pipe-pane into the per-party dir (group-readable so every attendee can grab a copy); party log --stop ends it. "What did we do last night?" for collectives, and the audit trail human+AI co-work needs.
party clean: remove the caller's own crash leftovers (dirs they own whose socket is dead), turning the manual rm -rf recovery in host's error message into a verb.

Group ergonomics: the default party group needs root and a relog before anyone's first party. On boxes where everyone already shares a group, host could offer (or default to) the caller's primary group when party doesn't exist. Fits the trust model; costs a little existence-confidentiality.
Matrix: live validation on NetBSD and DragonFly; one interactive attach/role/switch pass per release (automated coverage is all non-interactive).

No network transport: same-host is the perimeter; beyond it lies reinventing ssh.
No per-pane ACLs: tmux can't enforce them; faking it with hooks would be a leaky abstraction. Document the limitation instead.
No config files, no plugin system, no ACL syscalls: one POSIX file that runs on a 30-year spread of UNIXes is the identity; the 2026-04 simplification that removed per-OS ACL dispatch is not to be unwound.
Watch the file size: heavy why-comments are a feature; feature growth that pushes the single file far past its current size is not.