Cross-Venue Spot Idiosyncratic Down-Shock Rebound, Perp-Hedged: buy a post-2022 Bybit SPOT alt at the close of a day whose 2-day move lagged BTC by <=-2 sigma, short equal-dollar BTCUSDT.BYBIT perp, fixed 3-day clock (14 names disjoint from the promoted pre-2022 Bybit perp panel, 1-DAY, market-neutral event panel, max 2 new pairs per date)

Original Research Lead hypothesis (not seeded). It tests the long-side idiosyncratic down-shock template (lesson L266) on a different instrument type and a name-disjoint universe. The cash leg is Bybit SPOT and the hedge is the Bybit USDT perpetual, so the book spans two venues (BYBIT_SPOT + BYBIT). The template was promoted on iteration 1 on 29 pre-2022 Bybit USDT perps (185 trades, PF 1.67). Here every alt was listed on Bybit after 2022-01-01, so the universe shares no names with that panel. MECHANISM: when one alt falls far more than BTC over two days without a market-wide move, the excess drop is mostly forced or impatient idiosyncratic selling: a liquidation cluster, an unlock or large-holder exit, or a rumour. Liquidity providers who absorb that inventory demand a premium, and they are paid as the price partly recovers relative to the market over the next few days. Holding the alt in SPOT means the long leg is never liquidated and pays no funding. The BTC perp short removes market beta, as lessons L256 and L267 require for shock panels. EVENT, per alt, at each completed 1-DAY bar (bar timestamp = close, 00:00 UTC): W_alt = ln(close_t / close_{t-2}) on <ALT>USDT.BYBIT_SPOT; W_btc is the same quantity on BTCUSDT.BYBIT; X = W_alt - W_btc. Scale X by the alt's 60-day daily log-return std, measured up to the bar two days before the signal so the shock days are excluded, times sqrt(2): zx = X / (sd60 * sqrt(2)). If zx <= -shock_z (baseline 2.0), open a pair: LONG the alt on BYBIT_SPOT and SHORT an equal-dollar BTCUSDT.BYBIT hedge (hedge_ratio 1.0, pre-registered). Orders are market orders at the signal bar's close. On these 24/7 venues that price is the next bar's open, which is the platform's faithful equivalent of a next-open fill; I name the substitution here. Both legs exit on a fixed 3-day clock. PRE-STUDY (Research Lead, decoded catalog 1-DAY closes: alt from BYBIT_SPOT, BTC from the BYBIT perp, 2022-03 to 2026-10, at least 90 days of bars per name, one open event per name): at zx <= -2.0 with a 3-day hold, 161 alt legs fired on 77 distinct event dates. The mean hedged forward 3-day log return (alt minus BTC) was +2.30% per leg, median +1.33%, hit rate 61%, gross of costs. By year (legs, mean): 2022 3 / +5.1%, 2023 20 / +1.7%, 2024 60 / +2.5%, 2025 52 / +3.6%, 2026 26 / -0.75%. I state up front that 2026 is negative. At zx <= -2.5 the effect is larger (+4.31% mean, 70 legs) but there are only 31 distinct dates, below the ~60-date evidence floor in L271, so the baseline is 2.0. A 5-day hold decays to +0.27% mean (median -0.72%), so the edge is a short rebound and the clock must stay short. That is the main reason hold_days is capped at 4. COST ARITHMETIC: each event pays a spot round trip on the alt (~0.20%) plus a Bybit perp round trip on the equal-dollar BTC hedge (~0.11%), about 0.31% of the alt-leg notional. Against a gross +2.3% (median +1.3%) the capture is about 4-7x costs; a 2x shrinkage to ~1.15% still clears the 2x-cost bar. EVIDENCE COUNT (L238/L271): the effective sample is 77 distinct event dates, not 161 legs. CONCURRENCY (L267): at most 2 new pairs per date (when more names qualify, take the most negative zx) and at most 5 open pairs. Each alt leg is 10% of equity, so same-date gross long is at most 20%, total long at most 50%, and gross book at most 100% with the hedge. Drawdown expected near 10-15%. UNIVERSE (fixed list, point in time): APT, OP, ARB, SUI, SEI, INJ, TIA, PEPE, WLD, JUP, ORDI, LDO, ENA, GMX as <ALT>USDT.BYBIT_SPOT. A name becomes eligible only after 90 days of BYBIT_SPOT bars at that bar (is_listed()/listed_since(), parameters.point_in_time_universe = true). All 14 are still listed. Bybit serves no bars for closed pairs, so delisted spot names cannot be included. That biases the alt leg upward and is named as a risk. Corpus: BYBIT_SPOT is 0.1% of experiments; cross-venue is 10% against a 15% target; long-short is 25%. Distinct from in-pipeline items: BybitSpotAltPanelCapitulationAbsorption4H (unhedged, 4H, raw capitulation), BybitDisjointAbsorbedFlush* (perp, range/close-location trigger), BybitIdioAttentionShockContinuation (UP residual days, follows the move).