We formalise a layered balance-sheet model of the Reserve Bank of India's foreign exchange reserves that distinguishes gross headline reserves from effective deployable intervention capacity. The model incorporates (i) component decomposition with fungibility weights, (ii) duration-adjusted mark-to-market dynamics, (iii) the off-balance-sheet forward book with maturity laddering, (iv) a four-factor correlated shock framework driving Brent crude, foreign portfolio flows, USD/INR, and the US Treasury yield curve, (v) closed-form and Monte Carlo expressions for Value-at-Risk and Expected Shortfall on the effective reserve stock, and (vi) a barrier-hitting framework for crisis-threshold breach probability. Calibrated to RBI Weekly Statistical Supplement data of 1 May 2026, the central point estimate of effective liquid reserves is $447.7 billion against a headline of $690.7 billion; the 95% one-year VaR is approximately $84 billion and the one-year probability of breaching the IMF three-month import-cover floor is estimated at 4.1%.