Ask any enterprise software vendor about AI agent governance and they will point to access controls, audit logs, and compliance dashboards. All necessary, none sufficient. In this fifth article of the Future Enterprise series, we lay out what a purpose-built agentic governance architecture actually requires: five distinct layers that go well beyond security and compliance. We start with the governance gap (why an agent action can be secure, compliant, and still wrong), then define the full architecture: Access Governance, Compliance Governance, Behavioral Governance (confidence thresholds, behavioral baselines, goal alignment), Contextual Governance (bringing organizational awareness into agent decisions), and Accountability Governance (binding every action to a provenance chain). The article includes a practical graduated authority model for bounded autonomy, six design principles for building governance infrastructure, the organizational structures that need to accompany the technology, and a five-phase implementation sequence for enterprises starting from where most are today.