Works on my machine. And on the agent's.

Your laptop passes, the agent's sandbox passes, and prod crashes on its first order: a stale node_modules on one, an older Node on the other. Nobody ran the real thing. CI does: a clean machine on every commit, install, types, lint, tests, and a required check on main for the agent's thirty PRs a day. Unless it takes twenty minutes: cache installs, split tests, run only what changed. Not checked on a clean machine? Not checked.

Comment below: How long is your CI?

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.