Action Is Not Observation: A Declaration Gate Architecture for Constituting Action in Autonomous Systems

Autonomous systems operating in physical environments routinely record physical changes as system actions. Yet observation alone cannot establish that a physical change was caused by deliberate system intent: sensor artifacts, actuator faults, and environmental disturbances are physically indistinguishable from commanded outputs. This constitutive gap---the absence of a structural boundary between physical occurrence and action constitution--- creates an evidentiary failure in post-incident analysis and undermines accountability in human-robot interaction. We propose the Declaration Gate: an architectural component that enforces categorical separation between physical phenomena and constituted actions at the moment of occurrence. Transition across the boundary is permitted only through Declaration---a discrete, internal, irreversible, and non-retroactive event generated exclusively by system-internal conditions. We implement this architecture in Morpheus, an autonomous control system for armored vehicle platforms, and demonstrate across eight test cases that identical physical commands produce structurally distinct records depending solely on Declaration status. The contribution is architectural: a concrete mplementation of a boundary that prior work in speech act theory, hybrid automata, and philosophy of action has identified as necessary but has not realized as asystem component.