Deleveraging-Confirmed Spot Capitulation: buy a Binance SPOT alt at the close of a <=-2-sigma UTC day ONLY when its USD-M perp open interest (coin units) fell >=8% that same day, fixed 3-day clock (22 pre-2021 Binance spot alts, 1-DAY, long-only event panel, max 6 concurrent at 10%, flat most of the time)

Original Research Lead hypothesis. It conditions a down-shock liquidity-provision trade on a DIRECT marker of forced selling, as the analyst asked in the OKX stress-day post-mortem (2026-10-18): 'a materially different conditioning variable ... positioning/liquidation data that marks forced selling directly, rather than BTC return z-scores'. The marker is the one-day change in the coin's Binance USD-M perpetual open interest, measured in CONTRACT units (coins), so it is not mechanically linked to the price fall the way notional OI is. A large OI drop on a large down day means leveraged longs were closed: liquidations and margin calls, i.e. price-insensitive selling. Price-insensitive selling is the textbook case where liquidity providers earn a premium (Grossman-Miller 1988; Nagel 2012), and the perp flow is transmitted to SPOT by basis arbitrageurs who buy the perp and sell spot. A down day with RISING OI is a different event: new shorts are opening, which is informed or directional selling, and it should not revert. The trade is placed on BINANCE_SPOT (10.4% of the corpus against a 15% target; long-only and unlevered belongs on spot), using the perp OI only as a signal. There is no perp instrument leg: OI comes from the supplementary feed `open_interest_by_instrument`, which maps each `<SYM>USDT.BINANCE_SPOT` leg to the matching USDT perp's metrics mirror (5-minute Binance Vision OI, downsampled hourly, from 2021-12-01). Universe (point in time): 22 Binance spot alts, all listed on spot before 2021 and with USD-M perp OI history from 2021-12: LINK, ADA, DOGE, XRP, LTC, DOT, ATOM, ETC, BCH, TRX, XLM, FIL, AVAX, UNI, AAVE, SOL, NEAR, ALGO, VET, THETA, SAND, CHZ. A name is eligible at a bar only if it is listed (`is_listed()`), has at least 70 daily bars, and has an OI observation within 2 hours of both the current and the previous daily close; otherwise it is skipped (never a price-only fallback). Bars before 2021-12 produce no trades because there is no OI; the effective test window is about 2021-12 to 2026-10, roughly 4.8 years. Pre-registered event count (counted, not back-tested, on spot 1-DAY closes and metrics OI, 2021-12-03 to 2026-10-17): with z <= -2.0 and an OI drop of at least 8%, there are 310 name-events on 90 distinct UTC dates, about 19 dates per year. Per lesson L238 the evidence unit is the date, not the name-event: 90 dates is the honest sample. Neighbouring settings: z<=-2 with OI drop >=5% gives 419 events on 109 dates; z<=-2.5 with OI drop >=8% gives 193 events on 58 dates. Incremental-expectancy pre-registration (lessons L217 and L214): the comparator is the SAME down-shock rule without the OI condition, which the in-pipeline Binance spot capitulation panels approximate. Prediction: flush events (OI drop >=8%) have a mean 3-day after-cost spot return at least 0.5 percentage points higher than down-shock days where perp OI ROSE. If the flush subset does not beat the rising-OI subset, the OI conditioning adds nothing and the premise is falsified even if the panel is profitable. The developer logs, for every down-shock with z <= z_threshold, the OI change and whether it was traded, so the analyst can compute both subsets from the same run. Execution: decisions on the close of each 1-DAY spot bar (00:00 UTC). A market order at the signal bar's close is the faithful equivalent of a next-bar-open fill on this 24/7 venue (`next_bar_open_fill` is use_equivalent). There are no stops. Risk-control route (b): fixed time exit plus capped sizing (10% of equity per leg, at most 6 legs, so at most 60% gross, unlevered spot). Fee arithmetic: Binance spot round trip is ~0.20% (+ modeled slippage). A <=-2-sigma day on these alts is typically -7% to -12%. The promoted down-shock panels captured 1.0-1.8% per trade over 2-3 days. I expect a gross capture of about 1.3% over 3 days on flush events, so about 1.1% net. That is more than 5x the 0.20% round trip and clears the 0.25% spot floor. Buy-and-hold comparison (lesson L224): an equal-weight buy-and-hold of these 22 spot alts drew down roughly 80-90% in 2022. The panel is flat about 85% of days, with at most 60% gross, so its drawdown should be a fraction of that. I pre-register 25%.