Original Research Lead hypothesis. A price rise can be paid for by new money (buyers opening longs, so open interest rises) or by shorts closing (forced or voluntary buy-to-cover, so open interest falls). A short-covering rally is buying that ends once the shorts are gone: no new holder stands behind the higher price, so the move should give back some of its gain. This is the up-move counterpart of the factory's down-shock flush-vs-build classifiers ('Who Sold?' spread, OkxOiFlushVsBuildDownShockSpread, Cross-Venue Deleveraging-Confirmed Down-Shock Absorption). Those all classify DOWN days; this trades only UP days, which is a different set of events. Rule: at each UTC daily close, for each of 20 Bybit USDT perps listed before 2022 (LINK ADA DOT ATOM LTC ETC FIL XRP AVAX UNI AAVE NEAR ALGO XLM BCH TRX DOGE SOL SNX CRV), compute the day's log return z = r / std(prior 30 daily returns) from the Bybit bars, and the same coin's Binance USD-M open-interest day change z_oi = dlog(OI) / std(prior 30 daily OI log changes). OI is in coin units, read point-in-time from open_interest_by_instrument for the signal-only BINANCE legs, using the last value at or before each day close. If z >= shock_z (2.0) and z_oi <= oi_z_max (-1.0), short the Bybit alt at 10% of equity and buy BTCUSDT.BYBIT for the same dollar notional. Close both legs on a fixed hold_days (3) clock. Bybit is a 24/7 venue, so the order is a market order at the signal bar's close. That is the platform's stated equivalent of a next-bar-open fill. PRE-REGISTERED MEASUREMENT (lessons L230 and L217; fixed rule, run by the Research Lead before writing this; Bybit closes, Binance OI, 2022-01-15 to 2026-10): 134 qualifying events on 62 distinct dates. BTC-hedged 3-day forward return of the alt: -1.11% (5-day -1.33%). By year: 2022 -1.99% (30 events), 2023 -4.00% (27), 2024 -0.22% (17), 2025 -1.20% (20), 2026 +1.16% (40). So the short earns in 4 of 5 years, and 2026 is the counter-year. Incremental value of the OI classifier over the same up-shock without it: up-shocks with OI roughly flat (|z_oi|<1) returned +0.25% hedged, and those with OI rising >=1 sigma returned +0.39%. So the OI fall is what separates the losing rallies, not the up-shock itself. On the Binance USD-M price series of a 30-name superset the same arm gave -1.36% over 197 events on 84 dates. The OI-rising 'fresh longs' arm was too thin on Bybit (+0.39% hedged against a 0.22% two-leg round trip), so it is deliberately NOT traded. Cost arithmetic: two legs x 0.11% Bybit round trip = 0.22% of the alt notional, against an expected gross capture of about 1.1%, so net ≈ 0.9% per event, about 4x the cost. The analyst should count the 62 distinct dates, not the 134 events (L238). Risk control route (a): each alt short carries an intrabar protective stop at stop_atr_mult (3.0) x ATR(14) above its fill (supported intrabar stop, platform-matched). With daily ATR around 5% that is about 15% x 10% notional = 1.5% of equity, so at most 2% of equity at the stop. When an alt short stops out, its BTC hedge is closed at the same time. At most 5 concurrent events (100% gross maximum: 50% short alts / 50% long BTC). Leverage is at most 1x gross, well inside the conservative profile. An alt whose Binance OI series is missing for the day is skipped, never traded on price alone.