Byzantine-Proof Hardware via Non-Turing Silicon and Z3-Verified Invariants: A Formal Treatment of the Rice Theorem Boundary in Safety-Critical AI Governance

We establish a formal boundary between Turing-complete and non-Turing-complete enforcement architectures for safety-critical AI governance. By Rice's theorem, Byzantine fault immunity is undecidable for OS-based software guardrails. We present EHOX, a bare-metal ARM Cortex-R5F implementation with NRULES=31 hardcoded policy rules that is intentionally non-Turing-complete, and prove Byzantine immunity using CBMC (198 assertions, 0 violations) and Z3 SMT (43/43 theorems), covering 2^48 = 281 trillion discrete input vectors (coverage factor 1.88e12 vs RS105 physical tests). The system enforces a 44 ns hardware fail-safe on any APU dropout including EW jamming and HEMP-induced kernel panic. Physically demonstrated on AMD Kria KV260, St. Johann in Tirol, Austria. Literature review of 74 papers found no prior work combining these five properties. Includes LaTeX source for arXiv submission. Live endpoints: api.ehox.io/formal, api.ehox.io/epistemic. Hardware proof chain: Proof #305, SHA-256 NOR-Flash sealed.