Abstract AI governance is moving from retrospective review, policy documentation, and upstream alignment toward pre-execution control. As AI systems increasingly generate, route, approve, escalate, coordinate, and execute workflow actions, governance must operate before consequential action binds. The market now contains a growing number of tools, platforms, and frameworks that claim to provide execution governance, runtime safety, admissibility, trust envelopes, agent controls, operational authorization, or evidence capture. Many of these offerings may be valuable, but they are not all solving the same architectural problem. This paper proposes a vendor-agnostic reference architecture that separates execution-boundary governance into three distinct, interoperable planes: the Signal Formatting Plane, the Adjudication Logic Plane, and the Mechanical Enforcement Plane. The model helps organizations evaluate whether a solution prepares signals, adjudicates admissibility, enforces decisions, preserves proof, or combines several of these functions. EFA contributes most directly to the Adjudication Logic Plane by offering an open reference vocabulary for justified reliance, MECHA evaluation, consequence classification, human-state viability, authority state, evidence sufficiency, and the Dimensional-Collapse Gate. EFA also informs Signal Formatting and Mechanical Enforcement through substrate admissibility, runtime enforcement, SEF records, and forensic proof. This document does not claim that one framework, vendor, or technical pattern can solve all AI governance problems. Its purpose is to provide shared architectural language for enterprise leaders, regulators, auditors, system architects, vendors, and governance professionals. Keywords AI governance; structural AI governance; execution boundary; three-plane model; signal formatting; adjudication logic; mechanical enforcement; justified reliance; runtime enforcement; evidence packs; vendor interoperability; open reference architecture; non-bypassable governance; consequence-bearing systems.