Your agent called a method that doesn't exist

The agent writes cart.applyCoupon(), a method the cart doesn't have, and plain JavaScript ships it: "not a function" in prod on a Friday night. In TypeScript it's a red line in five seconds, before the file is saved. Turn on strict mode and every guess the agent makes is a red line it can read and fix. Then block the as any escape hatch with the no-explicit-any lint rule. The compiler is a reviewer that never gets tired.

Comment below: Is strict mode on in your project?

Brakes: a series on the checks that let an AI coding agent go fast without shipping bugs. Every best practice shortens the time between writing a bug and finding it. Brakes are why race cars go fast. All code is real TypeScript on Node 24, typechecked and tested before it went on screen.