r/ClaudeAI: Developer Ships 'brackish' — Open-Source Tool That Lets Two Claude Code Instances Negotiate an API Contract Across a Frontend-Backend Boundary Without Diverging

A developer released 'brackish,' an open-source coordination tool that addresses a recurring multi-agent coding failure: when two Claude Code sessions work on opposite sides of an API (e.g., FastAPI backend and React/TypeScript frontend), each independently makes assumptions about the boundary contract that quietly diverge. Brackish gives both sessions a shared negotiation layer to agree on the API contract before implementation begins, preventing downstream integration failures without requiring a human to manually reconcile the difference.