Structural Regime Classification of Credit Crises (Ω): Evidence for a Unique Drift→Break Event in 2008

Boundary note (added 2026-07-23): the Ω-centered empirical layer was self-retracted on 2026-05-31. Ω-centered validation is not currently supported as the active empirical basis; this record remains a historical, fixed, Ω-centered record and must not be cited as current validation. See the VOT Empirical Layer Boundary Note — https://doi.org/10.5281/zenodo.20474232. A later four-dataset head-to-head found that order gated by critical slowing does not beat free-energy signals (10.5281/zenodo.21422215, negative result). This preprint proposes a structural regime classification of credit crises based on Ω, a composite directional stress metric capturing both slope (structural drift) and accumulation dynamics. Using U.S. weekly credit and financial stress data spanning 1998–2023, we distinguish between: (1) Drift→Break regimes — characterized by prolonged slow deterioration followed by fast rupture (2) Shock-only regimes — characterized by fast rupture without preceding structural drift Empirical results show that among major modern credit stress episodes, only the 2008 crisis exhibits a two-layer Drift→Break structure. Post-2018 crises (2020 pandemic shock, 2022 tightening episode, 2023 bank stress) are shock-dominated fast regimes. Robustness is confirmed across alternative proxy definitions (HY-only vs HY∪STLFSI), event-set constructions (OR-union vs AND-overlap), and fast persistence sensitivity (k_fast = 4 reference, 3 boundary). The findings establish regime heterogeneity in systemic crises rather than homogeneous collapse dynamics.