Problem Parallel AI coding feels magical until both agents start maintaining their own version of reality. One agent remembers a rule from chat history. The other reads a repo note that is already stale. A workflow gets updated in one place but not the other. The user ends up repeating the same instruction twice, forwarding approvals manually, and cleaning up collisions that should never have happened. In practice, the user becomes the synchronization layer. Real cause The root problem is not "bad memory." It is multiple writable memory surfaces . If one agent treats a handoff file as live state, another agent treats a different file as live state, and both also rely on thread memory, the system has no clear authority. Drift is guaranteed. The same thing happens with parallel edits: no single place to check whether another lane is active no explicit ownership boundary no habit of writing what changed, why, and what not to touch The agents are not just missing information.…