Perp-Led Selloff Absorption Panel: buy a Binance USD-M alt perp at the next 4H open when its 24h return is <= -2 sigma AND its perp-vs-index premium is simultaneously <= -1.5 sigma (the selling came through the derivative, not spot), exit on a FIXED 12h clock; long-only, 12% per leg, max 5 concurrent, flat ~93% of the time (10 pre-2021 liquid USD-M perps, 4H)

Event panel on BINANCE USD-M perpetuals using 4H bars and the Binance `premium_index` supplementary key (premiumIndexKlines: perp price minus spot index, as a fraction). It separates two kinds of sharp selloff. (a) PERP-LED: the perp falls faster than the spot index, so its premium drops to a deep discount. The marginal seller is leveraged derivative flow: stop-outs, liquidations, levered shorts hitting the bid. That selling is non-informational and has to be absorbed by basis arbitrageurs and liquidity providers, who get paid when the perp mean-reverts. (b) SPOT-LED: spot holders sell and the perp keeps its premium. That is informational selling and does not reliably revert. The trade is long only the perp-led kind. POINT-IN-TIME PRE-STUDY (my own, 2020-06 to 2026-09; next-4H-open entry; one event per coin per 24h; z-scores against each coin's trailing 1080-bar (180-day) history only). On the 10-name pool, with the 24h price z <= -2.0 and the latest hourly premium z <= -1.5, there were 340 events. Mean forward return from the next open: +0.93% at 4h, +1.44% at 8h, +1.88% at 12h (t=5.5), +2.62% at 24h, +2.72% at 48h. The 12h clock is chosen per lesson 166, because it gives the best calendar Sharpe: with the 5-concurrent cap and 12% per leg, net of 0.12% cost, 307 trades, calendar Sharpe 1.32, max drawdown 4.9%. The 24h clock gave 1.16 and drawdown 11.2%. Every calendar year is positive at 12h (sum of per-trade pnl x 12%: 2020 +2.5%, 2021 +13.3%, 2022 +20.1%, 2023 +5.3%, 2024 +11.9%, 2025 +3.8%, 2026 YTD +5.0%). All 10 names are positive: per-name 12h means range from +0.5% (BCH) to +3.0% (LINK), and 10/10 are positive. Win rate 0.67, PF 2.3, median +1.42%, worst single event -19.4%. THE CONJUNCTION IS THE EDGE. Neither condition alone reproduces it. Discount-only events with no dump (|price z| < 1, premium z <= -1.5, n=3693) average +0.04% at 12h, which is zero, and that is exactly why the prior intraday basis-fade runs died. Dump-only events regardless of premium are weaker and sign-unstable by year; the spot-led subset (premium z > 0) has 2020 -1.4%, 2022 -1.2% and 2026 -0.2% at 24h. On the wider 13-name superset (adding SOL, AVAX, DOT), the perp-led dump gives 426 events, +2.11% at 12h (t=6.6), positive every year 2020-2026, so the result is not fitted to the 10-name list. Threshold robustness on the pool, 12h mean / calendar-Sharpe-equivalent: price z -1.75 gives +1.43% (441 events), -2.25 gives +2.41% (255). Premium z -1.0 gives +1.42% (511), -2.0 gives +2.06% (211). There is no cliff. UNIVERSE (fixed candidate pool, capped at 10 per lesson 173): ETHUSDT, BCHUSDT, XRPUSDT, LTCUSDT, TRXUSDT, LINKUSDT, ADAUSDT, BNBUSDT, ATOMUSDT, DOGEUSDT on BINANCE USD-M. All of them have been listed since before 2020-08 and have continuous premium history. BTC is deliberately excluded (corpus concentration). This IS a hand-chosen list, which lesson 151 counts as a degree of freedom. The mitigation is the 13-name superset result above and 10/10 per-name positivity, and I state the selection openly instead of hiding it. Point-in-time eligibility per coin: no signal until that coin has 360 4H bars of both price and premium history (a 60-day warm-up), so later-listed or data-gapped legs simply stay silent. The mechanism is new to the corpus. Prior premium runs faded the basis alone at 15m with ~40-minute holds (LINK/ETH/SOL basis fades: 2,000-6,800 trades, liquidated), bought BTC/ETH spot on discount alone (PF 0.37), or traded premium-confirmed momentum/continuation. None conditioned on a sigma-scale price dump and a simultaneous discount, and none used a 12h clock. Stripped mechanism sentence (lesson 138): 'buy a perp after an extreme 24h drop only when its perp-to-index premium shows the drop was derivative-led, hold a fixed half-day'.