A MARKET-NEUTRAL (dollar-neutral), TWO-INSTRUMENT relative-value SPREAD strategy on the ETH/BTC ratio expressed with the two most liquid Binance USD-M perpetuals (ETHUSDT.BINANCE long/short vs BTCUSDT.BINANCE the opposite leg, sized to equal-and-opposite USD notional so the book carries near-zero net crypto-beta). This is deliberately NOT a momentum, trend, breakout, funding, liquidation, order-flow, VWAP-reversion, or cross-sectional-rank strategy — all empirically dead here (L68-L92). The mechanism is MEAN-REVERSION of a HIGHLY-COINTEGRATED PAIR around a SLOW ADAPTIVE ANCHOR: ETH and BTC are >0.8 correlated, so log(ETH/BTC) is a near-stationary spread on week horizons even though the ratio itself trends for years. The critical design choice that separates this from the dead 'fixed-mean' pairs and from ETH/BTC relative-STRENGTH momentum (L68): the reversion target is a ROLLING mean (e.g. 30 daily bars), so the anchor RIDES the multi-year regime (2021 ETH outperformance, 2022-2024 decline) and we only trade deviations AROUND the current drift, never against the drift itself. We fade transient dislocations of the spread and let the adaptive anchor absorb persistent regime shifts. Rebalance/evaluate on DAILY bars; typical hold is several days to ~2 weeks. Deep multi-year Binance USD-M history on both legs means NO data wall (the recurring options/HL death mode) and a decisive out-of-sample sample.