fix: use kResidualGateProbeCount=64 at post-solver verification gates#34
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kyle-elliott-tob merged 3 commits intomasterfrom May 5, 2026
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Several post-solver verification sites left FullWidthCheckEval at the default 8-probe count while siblings on the same boundary used 64 — asymmetric verification depth without justification in the code or comments. The 64-probe count is the documented "residual-gate strength" that catches boolean-correct / full-width-incorrect false positives; the 8-probe default is for shape-deterministic rewrites. Closes the verification-probe-depth cluster from the 2026-05-04 audit: - signature-basis-55: ResolveLiftedSubstitute used 8 probes; sibling ResolveResidualRecombine uses 64 - signature-basis-cross-2: Singleton override-path bypassed the residual gate - signature-basis-cross-3: RunSignatureAnf accepted ProductShadow-repaired Expr after only 8 probes - expr-foundation-5: IsSpuriousFullWidth 8-probe sample insufficient for sparse-dependence Adds `inline constexpr uint32_t kResidualGateProbeCount = 64;` and `kDefaultProbeCount = 8` in SignatureChecker.h, then uses the strengthened count at: - ResolveLiftedSubstitute's post-substitution verifier (matches the sibling residual-recombine site at line 709) - RunSignatureSingletonPolyRecovery override-path (matches the non-override path's recursive residual gate) - RunSignatureAnf's RepairProductShadow re-verifier (the AND/MUL semantic boundary V2 already flagged as a known divergence) - IsSpuriousFullWidth's per-variable spurious-classification probe Refactor only — full unit suite (1171 tests) still passes; the strengthened verification did not surface any test deltas.
…obe-depth-cluster
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Summary
Closes the verification-probe-depth cluster (4 findings) from the 2026-05-04 audit. Several post-solver verification sites left
FullWidthCheckEvalat the default 8-probe count while siblings on the same boundary used 64 — asymmetric verification depth without justification in the code or comments. The 64-probe count is the documented "residual-gate strength" that catches boolean-correct / full-width-incorrect false positives; the 8-probe default is for shape-deterministic rewrites.Findings closed:
signature-basis-55— ResolveLiftedSubstitute used 8 probes; sibling ResolveResidualRecombine uses 64signature-basis-cross-2— Singleton override-path bypassed the 64-probe residual gatesignature-basis-cross-3— RunSignatureAnf accepted ProductShadow-repaired Expr after only 8 probesexpr-foundation-5— IsSpuriousFullWidth 8-probe sample insufficient for sparse-dependenceChanges
SignatureChecker.hdeclaresinline constexpr uint32_t kDefaultProbeCount = 8;andkResidualGateProbeCount = 64;ResolveLiftedSubstitute's post-substitution verifier passeskResidualGateProbeCount(matches the sibling residual-recombine site at line 709)RunSignatureSingletonPolyRecoveryoverride-path passeskResidualGateProbeCount(matches the non-override path's recursive residual gate)RunSignatureAnf'sRepairProductShadowre-verifier passeskResidualGateProbeCount— the AND/MUL semantic boundary V2 already flagged as a known divergenceIsSpuriousFullWidth's per-variable probe useskResidualGateProbeCount(was 8)Test plan
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