Semantic Contracts: A New Layer to Verify AI-Generated Code at Compile Time

The article diagnoses a fundamental shift in software engineering. The traditional waterfall pipeline—Requirements through Deploy—provided multiple human checkpoints and thus a chain of trust. AI-driven development (termed "Vibe Coding" in the piece) collapses this into a single prompt-to-code step, creating four distinct trust failures: unknown AI behavior (from billions of parameters), untraceable bugs, unpredictable fixes, and the impossibility of human code review at AI generation speeds. The proposal reframes the problem not as a need to understand AI decision-making, but as a need for a new intermediate layer that makes correctness a structural property of the system itself.

Semantic Contracts draw on decades of formal verification research but reject its approach. Rather than trying to mathematically prove correctness after code is written, they enforce correctness through process guarantees—using simple, composable building blocks (combinators) with predictable rules that the compiler can verify at build time. This shifts the burden from post-hoc review to design-time structure. The article illustrates this with two examples: a sorting algorithm (where the contract structure prevents recursion errors) and an e-commerce checkout (where explicit state returns force handling of InsufficientBalance and InsufficientStock cases). The approach treats business logic as a type system, allowing safe composition, instant verification, and implementation swaps—a significant departure from the current ad-hoc tangle of if/else statements and error handling.