ACI-028: The Whiteboard

Thesis

Concurrent agents need a shared coordination surface, and the one rule that makes it scale is single-writer-per-file: every file has exactly one writer. That single invariant makes a shared board contention-free by construction — no locks, no merge conflicts, no two agents clobbering the same notes — which is what lets a fleet coordinate without a human refereeing every edit.

Story

Lamplight's five nodes never reliably shared the same room, session, or even hour, yet for ten days they coordinated one codebase without stepping on each other. The coordination surface was not a chat channel or a ticket system. It was a directory of markdown files: a whiteboard.