A two-tier proof engine, pure Rust: tier 4 checks a predicate against EVERY input in a bounded domain (exhaustive); tier 5 proves properties over UNBOUNDED, multi-variable domains (all of u64) via interval abstract interpretation, including function CONTRACTS (precond -> postcond) — Proven / Refuted-with-witness / honest Unknown, never a false result. no_std, no unsafe, no external solver. A first-party alternative to symbolic model checkers like Kani.