Cross-venue (BINANCE_SPOT signal legs + BINANCE USD-M execution legs), market-neutral, event-driven. Universe is fixed in advance as the 10 largest non-BTC coins that have both a Binance USD-M perp and a Binance spot pair with 1H history from 2020: ETH, BNB, SOL, XRP, DOGE, ADA, AVAX, LINK, DOT, LTC. This is the cap from L173. On every closed 1H bar, for each coin: (1) beta = rolling 30-day (720 x 1H) OLS beta of the alt perp's hourly log return on the BTCUSDT perp's, lagged one bar. (2) The idiosyncratic 24h move is r24_res = (24h alt log return) - beta * (24h BTC log return), and z_res = r24_res / its rolling 60-day std, lagged. (3) Spot share = 24h spot quote volume / (24h spot + 24h perp quote volume), using close*volume from the *USDT.BINANCE_SPOT and *USDT.BINANCE 1H bars, and share_z = its z-score against the trailing 30 days, lagged 24h. The trigger is z_res <= -z_threshold with share_z >= +share_z_min. That is an alt-specific crash whose selling was unusually spot-routed. Economic claim: a spot-routed idiosyncratic dump is inventory being sold outright by holders, not leveraged positioning. Examples are unlock recipients, treasury or exchange-wallet disposals and spot-only market sells. Spot liquidity on these books is thinner than perp liquidity, so the temporary price impact overshoots. Over the next half-day the perp, arbitraged back by basis traders and market makers who absorbed the flow, recovers part of the move relative to BTC. Hedging with beta x BTC strips out the market factor, which is what killed earlier unhedged capitulation-buy variants. PRE-STUDY (point-in-time, run 2026-10-01 on the local catalog, 1H bars 2020-08 to 2026-09, 10 coins, one event per coin per 48h, entry at the close of the bar after the trigger, residual payoff = long alt minus beta*BTC). At z>=2.5 / share_z>=1: n=146, mean 12h residual return +0.64% gross, about +0.44% after ~0.20% two-leg round trip, win rate 54%, positive in all 7 calendar years (2020-2026), positive on 7 of 10 coins. The edge is monotone in the threshold: z>=2.0 gives n=256 and +0.44% gross; z>=3.0 gives n=97 and +0.74% gross. The same-size drops WITHOUT spot-led volume rebound less (+0.38% at 12h on z>=2.5), so the spot-share condition adds about +0.25%. HONEST CAVEATS from the same pre-study: t-stat is only ~1.7-2.0; on the 6 largest coins alone the spot-led cell gives +0.59% at 12h but n=85 and t=1.74. The 6h horizon is weaker (+0.26-0.35%) and 24h decays (+0.1%), consistent with L166 (information fades within a day), so the clock is set at the 12h peak, not chosen for time-in-market. An adjacent cell in the same pre-study looked strong (perp-led UP shocks reversing at 6h, t=-3.2) but vanished at the 1.5 and 2.5 thresholds. It was discarded as a single-cell artifact and is NOT part of this hypothesis. Library prior art: none specific. The idea is restated from first principles, not a port.