My AI agents were individually correct and collectively a disaster

TL;DR: Multi-agent systems don't have an execution problem, they have a coordination problem. I built a gatekeeper layer called Nexus that sits above all other agents and is the only one that can create a ticket. Repo: https://github.com/PermaShipAI/nexus When I started building multi-agent systems for software engineering tasks, at first, the architecture felt obvious. Create specialized agents for things like security, reliability, test coverage, and performance. Point them at a codebase and let them run. The problem showed up fast. The agents were individually correct. For example, the CISO agent found a real vulnerability and proposed a patch. The SRE agent identified the same affected component and proposed an architectural change that would eliminate the entire class of problem. Both of the proposals were valid but neither agent knew the other existed. They would have shipped conflicting changes to the same files. That's the easy version of the problem. The harder version was age