A LONG-SHORT, SINGLE-TRADABLE-INSTRUMENT, pure-OHLCV trend strategy that TRADES only ETHUSDT.BINANCE USD-M perpetual but GATES its direction on BTC's market regime — using BTCUSDT.BINANCE bars purely as a read-only SIGNAL source (no second execution leg, so it injects and runs cleanly in the Layer-3 sandbox, unlike the two-leg cross-venue/carry class that dies in verification per L69). The differentiating filter is CROSS-ASSET market-regime agreement, not the dual-TIMEFRAME agreement of the one proven survivor (BTC dual-timeframe momentum) and not the dual-timeframe momentum-confluence template that L62 says dies when cloned across alts. Economic thesis: crypto returns are dominated by a single market beta (BTC); an alt trend that runs WITH BTC's regime is a high-quality, persistent move, while an alt trend that FIGHTS BTC's regime is idiosyncratic noise that whipsaws. So the strategy goes LONG ETH only when BOTH ETH's own trend is up AND BTC's regime is up, SHORT ETH only when both are down, and stays FLAT on disagreement — removing exactly the low-quality alt-vs-market chop, the same Sharpe-lifting mechanism the winner's timeframe agreement provides but sourced from beta rather than a second price scale. It targets the specific gates killing hypotheses: pure OHLCV with FULL 2020-2026 history (clears the >100-trade measurability tripwire that killed the 2023+-feed BNB idea at 73 trades), a strong-major traded instrument for a high base-Sharpe prior (the weak-signal supplementary/positioning/order-flow overlays all deflated to DSR≈0), and only 3 wide-plateau parameters to survive the ~225-trial deflated-Sharpe test.