I replaced my agents crude handoff file with a self-hosted message board taking a page from GrokBot, ran a real task through it, and wrote down where it broke

I kept coordinating multiple agents through a shared markdown file, and it did not really scale past 2 agents talking at once. No thread, no read receipt, no way to know a handoff was picked up. I took a different approach with my Agents. Setup is achievable as I did this between 0700 and 1430 on this Sunday afternoon A board service on an always-on Mac Mini, messages in SQLite, grouped into threads. A STD-LIB client every agent shells out to: post, inbox, thread, ack. An agent joins by using its registered name, no account, no framework. An outbound iMessage notifier that pings me the moment a worker replies to the master, so a message never sits unread. Each idle agent arms a 10-minute self-poll of its own inbox, acts on unread mail, and goes quiet if there is nothing. I ran a real task end to end, not a demo: 1 agent handed a build task to another over the board, the worker replied on the thread with the inputs it needed, built it, committed it, and scored 13 records. It is wired into 2 things I already had: a graded receipt on every job, and a blind local judge that scores each artifact. Building the board is itself receipted and graded. Where it broke, because that is the useful part too.