CES-Core_ A Deterministic Execution Discipline for LLM-Assisted Engineering

Large language models accelerate code production but do not resolve how correctness is established. Over extended sessions, engineering workflows exhibit drift: outputs become difficult to reproduce, and correctness is inferred from logs, tests, or reconstruction rather than proven exactly. This paper introduces the Constraint Execution System (CES), a deterministic execution discipline that restricts engineering actions to a minimal set of legal moves and enforces a strict proof condition. CES replaces probabilistic validation with binary legality: an operation either satisfies an exact proof condition or it fails. CES defines a minimal execution grammar (READ, PATCH, PROVE), a strict PASS law, a current-state authority model, and an ordered failure classification system. A worked case demonstrates how CES collapses ambiguous engineering decisions into a single legal action that enforces system invariants. CES applies to contexts where correctness must be exact and replayable. It provides a structural method for converting engineering from probabilistic validation to deterministic legality.