Why do my protocol's economic invariants collapse under real trading after five audits?

Static analysis and fuzzing tools catch roughly 90 percent of low-level smart contract vulnerability patterns such as reentrancy, overflow, and access control, but a four-year empirical study published in 2026 found they detect only 8 to 20 percent of exploitable bugs in production. The gap is in economic and mathematical invariants: rounding direction under adversarial sequences of operations, precision loss compounding across hundreds of pool interactions, and slippage compositions across multiple markets. These bugs do exactly what the code says to do; the specification itself contains the flaw. In November 2025 Balancer lost $120 million through a rounding direction error that cleared multiple audits because every tool tested individual operations rather than sequences of thousands. Roughly 90 percent of contracts exploited in 2025 had been audited at least once.