Harness engineering is the work of setting up the environment around an AI agent so it can do useful work more safely and reliably. This may include clear instructions, approved tools, saved task state, and checks for the result.
Think of a workshop prepared for a helper: the right tools are on the table, the rules are visible, and there is a place to check the work before it leaves.
The AI model is only one part of the system. A good setup can make its work easier to guide, but it cannot guarantee that every answer or action is correct. People still need to choose sensible limits and review important results.