Observer–Observed Cancellation as a Terminal Interface Condition(Zero Is Not a Result_System Engineering Environment Initialization)

This document records a terminal interface condition in which observer and observed are symmetrically represented within the same interface description. It is not a model, equation, or theory, and it does not provide causal explanations, predictive claims, or computational procedures. The expression used in the document functions as a state expression, not as a formula, and serves solely to mark a stopping boundary beyond which further reduction or interpretation is undefined. Within the CMEM-compatible framework, this note operates as an interface seal: a structural record indicating that when mutual observation is fully admitted, no invariant remainder can persist without reintroducing asymmetry. The document therefore does not answer questions of “why” or “how,” but delineates where interpretation terminates.