Modern fintech demands deterministic precision. In finance, there is no room for approximation—every minor fractional unit must remain 100% audit-compliant. Yet JavaScript, the backbone of client-side web applications, introduces structural challenges through IEEE-754 floating-point arithmetic. A single rounding drift can compound across amortization schedules and ledger balances. To address this challenge and establish local currency primitives, we launched FinEngine —an open-source comp...