Episode 123 of The Technical Co-Founder Podcast dives into formal verification for smart contracts. Lucas and Luna explore how one early-stage startup, Quantify Labs, mathematically proves the correctness of DeFi smart contracts before deployment. They break down the difference between fuzzing, auditing, and formal verification, and walk through a concrete example where formal verification caught a critical reentrancy bug that static analysis missed. The hosts discuss the trade-offs: the steep learning curve of writing specifications in TLA+ and Coq, the computational cost of symbolic execution, and why the startup decided to pay that cost upfront rather than risk a million-dollar exploit. They also touch on the broader industry trend of insurance underwriters starting to require formal verification for high-value DeFi protocols. Listeners learn what formal verification actually means in practice, why it's different from traditional testing, and whether it makes sense for their own stack.