ACI-041: The Fence

Thesis

A written rule cannot tell you when you stopped following it, so pair it with a fence: a test that asks the system's own source of truth what exists, reds on anything new and unguarded, fails when stale, keeps no exemption registry and lands with the mechanism it guards. Prove the fence can see, give its thresholds headroom, and declare a known red rather than skip it. Absence is established the same way, never by a search: derive the population from the structure and ask what each member must have.