Governance becomes real at the door, or it does not become real at all.

An agent is a new kind of employee, and it needs three things governed: the brain, the hands, and the worker itself. One door each. A failure at the model door is a bad sentence; at the tool door, a bad action; at the agent door, a bad actor. That single split is what makes the control set MECE — every guardrail in this guide lives behind exactly one door. What follows walks all three doors in breadth and depth, tests what else claims to be one, specifies the protocols they carry, and covers the scanner layer attached to them, the data entitlements they must resolve, where they are deployed and how they behave under load, the control plane that decides above them, the obligations they evidence, the vendors that implement them, and a loan lifecycle that proves them. Five lenses per concept: what it requires, how to architect it for a bank, a flow diagram, a plain-English reading, and what it hands off next.