In a sanctioned petrostate, external currency value is governed by the parallel bazaar exchange rate rather than the central bank's nominal peg. When sanctions restrict secondary banking clearing channels and discount illicit crude exports:

• Current Account FX Deficit: Usable USD inflows collapse as discounts (20–40%) and laundering fees (15–30%) eat export proceeds.
• Fiscal Seigniorage: Budget shortfalls are funded through domestic central bank overdrafts, expanding M2 without real output backing.
• Private Substitution: High inflation expectations drive households and companies to swap rials for physical greenbacks, gold coin, or stablecoins (USDT), accelerating the parallel rate spike.
• Runway Horizon: Once liquid central bank FX reserves hit minimum operating thresholds ($3B–$5B for vital medicine and staples), parallel currency depreciations turn non-linear.

This simulator is calibrated against empirical data from Iran’s 2012, 2018–2020, and current maximum pressure episodes:

• Baseline Base Crude: $80/bbl benchmark, assuming shadow tanker transshipment costs.
• Official Peg: Normalized at 420,000 IRR/USD (NIMA governmental clearing window for state-approved grain imports).
• Pass-Through Coefficient: 0.42 to 0.58 elasticity of domestic consumer CPI to open-market FX moves over a 6-month lag.