Keel

A ship's keel is the reference line everything else is measured from. It is also what keeps the ship from capsizing — an even keel is a stability property, not a decoration.

Keel measures one thing:

A check is only a check if the signal it reads comes from somewhere the thing being checked cannot write to.

Most verification in an agent-maintained codebase fails this. An LLM reviews what an LLM wrote. A doc is validated against another doc. A status field says "passed" because something set it to "passed". The pipeline is green and nothing has been verified.

The classification