Teams building with AI usually end up building two products: the thing they ship, and the system around their agents that makes them useful in building the thing they ship.
We built such a system to help us ship Nimbalyst. We call it our team harness. This post is about what we learned from doing it.
What a harness is
A harness is the durable layer around a model: instructions, tools, permissions, context, and verification.
Claude Code and Codex are harnesses in this sense. Each wraps a model with a system prompt, a tool surface, a permission model, and an execution loop. Anthropic and OpenAI own that layer.
