The 15% Bug Catch: What Type Systems Actually Deliver

Static type checkers are often sold as silver bullets for code quality, but the landmark 2017 study by Gao, Bird, and Barr found they catch only about 15% of public JavaScript bugs. This episode climbs the operational ladder of gradual typing — from two-tier configs and per-module ratchets to the human decision points where automation stops. We explore why AI coding agents make escape-hatch counters essential, how production type tracers produce raw material that still needs human judgment, and why runtime validation with Pydantic or Zod at trust boundaries is non-negotiable. If you've ever wondered whether your type checker is buying you real bug prevention or just expensive autocomplete, this episode walks through what the data actually says. Episode #300060 — open it directly at myweirdprompts.com/300060