adstrate

The off-record referent tier beside the substrate (ad- alongside, as sub- is under): a referent category facts can bind to but not contain — content (CAS), state (cell), flow (wire) — under an identity discipline that keeps every binding re-checkable. Interface in facts, payload off-record; implementations are ordinary occupants. Theories hold the substrate's irreducible judgments; the adstrate holds its irreducible referents. Anything implementable through facts (policies, profiles) is not adstrate — cell's status is open for exactly that reason. First-class in the topology since ADR 0018: layer "adstrate" marks implementations and drives two invariants (substance never depends on adstrate; adstrate never depends on downstream). Naming: Greek marks the substrate, Latin the adstrate — working names corpus (content), tabula (state), cursus (flow) — and arche-* names occupants.