Material Signatures for Antineutrino-Based Detectability of Covert Fissile Production in Fusion Reactors

Antineutrino monitoring is a promising route for early safeguards signals, but fusion-adjacent deployment requires robustness to prior disagreement, detector nuisance variability, and transfer stress. We present a hybrid formal-empirical framework that combines contradiction-aware sequential calibration, an information-decomposed minimum detectable diversion criterion, and finite robust detector-material co-design. The method is grounded in source-lineaged reactor-spectrum and safeguards detection formalisms and extends them with manuscript-defined robust operators. We execute a CPU-only benchmark over 17,280 runs spanning prior families, drift rates, standoff distances, and detector resolutions with matched false-alarm operating points across comparators. Formal consistency checks pass for all theorem-linked symbolic obligations (4/4). Empirically, the robust method achieves strong delay robustness (delay win rate 0.9965 versus single-prior likelihood ratio; median delay ratio 0.6943 versus fixed-threshold test-statistic baseline), supporting the detectability-improvement claim under the tested open-parameterized regime. However, calibration and transfer closure remain conditional: calibration violation rate is 0.9524, leave-one-prior-out FAR inflation p95 is 1.2871, and hard-versus-easy transfer degradation ratio is 1.5402. These outcomes establish a defensible contribution boundary: robust detectability gains are supported, while policy-grade calibration and transfer claims require targeted recalibration and transfer-stability refinement. The manuscript reports both supported and mixed claims through explicit claim-evidence linkage, enabling reproducible iteration rather than optimistic overclaiming.