Context
I run more than one AI coding session at a time (Claude Code, in my case). One is usually the planner: it holds the architecture, decides what to do, splits the work. The others are executors, and each takes a chunk and grinds through it.
The problem is that these sessions cannot talk to each other. Every terminal is its own island, so I became the message bus. I copied a plan out of the planning session and pasted it into an executor. I copied the result back. I re-explained context that one session had and another needed. Every handoff went through me, by hand, one clipboard trip at a time.
TL;DR: downbeat is a small, local, human-in-the-loop message bus that lets parallel AI coding sessions on one machine hand tasks to each other and read the replies back. No cloud, no account, no network. It is on PyPI now: uv tool install downbeat.
I was the message bus, and it fell apart at four sessions
