The 'plan lives in one person's head' framing is a good one, and the action/check/rollback triple per step is the part I'd copy even without an agent. One question: when an agent writes the checks, how do you stop it from writing checks that merely confirm its own actions (e.g. 'terraform apply succeeded') rather than independent ones like probing the DB port from outside the VPC? Also, the one-action-at-a-time limit seems wise; I'd be curious whether rollback steps get the same human approval gate as forward steps.