The first SIZEABLE, honestly-verified reasoning capability — built on CORE's
own terrain (exact, verifiable, deterministic), not GSM8K's stochastic terrain.
THE OPERATOR (generate/proof_chain/entail.py, ADR-0206):
- evaluate_entailment(premises, query) -> entailed | refuted | unknown | refused.
- The multi-hop inference operator evals/symbolic_logic/gaps.md said did not exist
("no operator that takes A->B, B->C and returns A->C") and ADR-0205 deferred.
- Built on the ADR-0201 ROBDD canonicalizer: premises |= Q iff (AND P) -> Q is a
tautology. SOUND AND COMPLETE for propositional logic, not single-step.
- wrong=0 is structural: an exact tautology check refuses (LogicError) on
malformed / out-of-decidable-regime (quantified/predicate) input, never guesses.
THE HONEST METRIC (evals/deductive_logic/):
- holdout v1 (500 cases): 500 correct / 0 WRONG, incl. 227 non-trivial deductions
(117 entailed + 110 refuted). dev (200): 200/0.
- Gold from an INDEPENDENT truth-table oracle (oracle.py) sharing zero code with
the engine. 8,000-case fuzz across two independent decision procedures:
0 disagreements. This is the soundness evidence the GSM8K composer could never
produce (it could not separate its 2 right from its 87 wrong answers).
- contract.md states the load-bearing honesty boundary: PROPOSITIONAL ONLY, and
given-formulas (NL->logic grounding is a separate later layer, kept out of scope
so we do not re-step on the GSM8K natural-language rake).
TESTS (17, all green): classic inference shapes (MP, multi-hop chain, modus
tollens, disjunctive/hypothetical syllogism, conjunctive rules, genuine unknown),
refusal boundary (inconsistent / quantified / predicate / malformed), and a
deterministic engine-vs-oracle fuzz cross-check.
Pure new module — does NOT touch serving. Smoke 73 passed; invariants 40 passed.
