Cross-window z-score differential trigger — the generalized crossover primitive. Pass two metric_ids (typically same factor at different windows, e.g. VOL_RV_7D vs VOL_RV_30D) and a threshold. Fires on the delta z(a) − z(b). Same institutional envelope. Applies across every factor family: TR, VOL, FLOW, FUT, OB, CORR. Backtests run over the CRYPTYX 200+ tracked digital assets — BTC, ETH, SOL, top-cap + long-tail coverage.