The Human Layer.

The Human Layer is the architectural layer that connects human judgment with artificial intelligence: the set of structures - decision gates, escalation protocols, accountability structures, override mechanisms and trust calibration interfaces - through which AI systems remain governed by, and accountable to, the humans responsible for their outcomes.

AI systems designed to amplify human judgment outperform systems designed for full replacement - across field evidence, by roughly a factor of three. But amplification does not happen by intention; it happens by architecture. Without a designed Human Layer, oversight degrades into rubber-stamping, accountability becomes untraceable, and organizations inherit the liability of decisions no human meaningfully made. In regulated and trust-dependent environments, the Human Layer is not an enhancement - it is a legal and structural requirement.

Introduced in the first paper of the Human Layer series as a design principle, an economic argument and an infrastructure requirement; specified as a five-component architecture in the second paper; made measurable in the third.