Two teams can use the same model, write the same prompt, and get completely different results.
The difference is often not the model. It is the repository around it.
One repository gives the agent durable instructions, scoped rules, tests, linters, CI feedback, and hooks that stop dangerous actions. The other gives the agent a README and hopes for the best.
That surrounding control system is the harness.
Harness Score is a free, open-source, deterministic scanner that measures how much of that system a repository actually has. It checks filesystem evidence across Cursor, Claude Code, Windsurf, Cline, Continue, Codex, Copilot, and other tools. It then returns a maturity level from L0 to L4, a score across six dimensions, and a ranked list of what to improve next.
