Abstract: This paper introduces Deterministic Boundary Layers (DBL), a minimal architectural model for governing non-deterministic systems with deterministic, auditable outcomes. DBL separates normativity from execution by construction: all normative effects are expressed exclusively as DECISION events recorded in an append-only event stream, while execution outputs are treated as observational and non-normative. Governance decisions are deterministic functions of authoritative inputs admitted by a boundary layer, independent of execution behavior, timing, or infrastructure. This separation yields four structural consequences: deterministic governance under non-deterministic execution, invariance of G/L separation, replay equivalence of normative state without re-execution, and observational non-interference. Context: This work builds on the companion paper "Execution Without Normativity" (DOI: 10.5281/zenodo.19600773), which formalizes the pre-normative execution substrate. A reference implementation is available at https://github.com/lukaspfisterch/dbl-gateway.
Pfister Lukas (Thu,) studied this question.