The Cybernetic Sustainability Loop: Governed Agentic Systems on a Sustainability Data Plane

Carbon-aware computing today is one-way: systems consume gridcarbon-intensity feeds, but publish nothing machine-readable about their ownfootprint, so no system can react to another. This article describes and evaluates,in three independent ways, a reference architecture for closing that loop:executable fitness functions run through a shipped governance gate, livemeasurement of the public data plane, and simulation of the governor on realgrid-carbon traces. Services publish runtime sustainability metrics at a well-knownURI defined in an IETF Internet-Draft; agents discover and consume peers’endpoints; carbon state, evaluated against normative criteria, maps onto afive-rung verdict order—allow, degrade, escalate, block, terminate—behind onegovernance gate with human approval. Physical demand response is specifiedthrough typed tool servers exposing open electric-vehicle-charging protocols. Thecore is hexagonal: ports inside, every external system an adapter. The articlestates plainly what is implemented, what is designed, and what is open.