Parallel sessions need a mailbox, not a transcript paste

The Skillsync Show HN (49743049; txcript as the converter) and repos like automatis-tools/agents-can-communicate point at the same operator pain: when two coding sessions run in parallel, pasting a transcript into the other chat is not coordination. You need a mailbox — a place to leave decisions, blockers, review asks, and unfinished work that another independent session can pick up without inheriting the wrong turn schema.

A paste collapses attribution, drops tool-call evidence, and forces the next session to re-derive context from prose. A mailbox keeps sessions local and permission-scoped while still letting them ask each other questions, exchange reviews, and hand off mid-feature. Treat “paste the thread” as the failure mode; treat durable handoff messages as the control.