How I Made Two Claude Code Instances Talk to Each Other (With JSON Files, Obviously)

The Problem Nobody Asked Me to Solve I had two Claude Code sessions open. One was writing backend code. The other was running tests. And I thought: "Wouldn't it be cool if they could just... talk to each other?" Narrator: it would be cool. It would also take several days, involve undocumented APIs, and teach me more about Windows file locking than any human should know. Why Files? Why Not HTTP? When you're running multiple AI agents on the same mac