Interface Override: A Definition of a Structural Condition in AI-Mediated Content Delivery

A formal definition of interface override, a structural condition in AI-mediated content delivery in which a generative mediating system creates and serves its own user-facing surface, rather than transforming the source's content for presentation. The definition distinguishes interface override from transformation, substitution, and disintermediation; specifies its behavioral signature (variance by user and query, non-observability, non-persistence); and locates it in relation to the author's prior work on invariant design and meaning debt. The definition is explicitly behavioral rather than architectural: it describes what a mediating system does when operating under interface override, not how such a system is implemented. This document introduces the term; empirical characterization and detection methodology are reserved for subsequent work.