Market-neutral calendar spread on Binance COIN-M (inverse) BTC contracts: long the BTCUSD_PERP perpetual and short the nearest BTCUSD_YYMMDD quarterly future when the annualized basis between them >= 8%. Both legs are BTC-margined (inverse contracts), so P&L is realized in BTC — making this a BTC-yield-enhancement trade for holders alongside a USD-neutral spread. The edge is mechanical: dated quarterly futures MUST converge to the underlying spot/perp price at expiry by contract specification, so a quarterly trading at a premium to the perp guarantees price compression as expiry approaches (basis = mark_quarterly / mark_perp - 1, annualized over days_to_expiry). This is fundamentally different from the failed ETH/BTC ratio mean-reversion: there, the 'ratio' between two distinct assets had no contractual force pulling it together and could trend indefinitely. Here, the basis between two contracts on the SAME asset has a hard contractual convergence point. Targets the most-underrepresented venue bucket (BINANCE_CM at 0.9% vs >=5% target) while also adding to long-short (12.4%), pairs scope (18.0%), and introducing a 'basis carry / cash-and-carry' mechanism class never tested in the portfolio. OHLCV-only — no supplementary data dependency, no classical TA patterns, no ratio reversion on distinct assets, simple 2-leg position.