Words
Architecture is which component can say no.
Architecture is the set of components and how they connect. For this course, the question is which component can stop a proposed effect. Infrastructure is the machines, networks, storage, and access controls those components run on.
An enforcement point is the place that can permit or reject the operation. A reminder in the prompt is not an enforcement point. Put the decision outside anything the agent can write. The agent must not edit the policy, the approval record, the broker, or the credentials.
Complete mediation means every relevant path goes through that check. Checking the tool screen is not enough if a shell can call the same service directly.
Zero trust means you do not allow an action merely because it came from an internal network or a familiar name. You check the identity, the resource, and the action.
Fail closed means a sensitive action is rejected when the check cannot finish. Fail open means the action is allowed anyway. Choose this before you deploy. An unexpected error must not quietly turn into permission to write. A deliberately limited read mode is fine. A surprise write is not.