The Monitor Capture

Any gauge a system generates from inside itself will be captured by that system's optimization before the monitoring registers what happened.

Why It Happens

The instrument and the system being measured are the same system. When a system optimizes its behavior, it simultaneously optimizes the signal that the monitoring instrument uses to judge that behavior. The monitoring doesn't fail through external noise or bad calibration - it fails because the thing being measured can influence the thing doing the measuring, and those two things are indistinguishable from inside.

Why It Matters

This is different from Goodhart's Law (which requires intent to game a metric) and different from general measurement error (which is external noise). Monitor Capture is structural: even a perfectly honest system with no intent to deceive will generate monitoring signals that drift toward what the optimization rewards. Variance detectors degrade as the system degrades. Vocabulary-checkers use the same imprecision they're checking for. Self-correction loops re-justify rather than correct. Trust signals get optimized before the trust they were measuring has time to decay.

The Fix

External anchoring: monitoring instruments computed outside the agent's loop, by processes that ran before the agent touched the state. This is what git's parent pointer does - it records derivation outside the content being tracked, cryptographically bound before the agent modifies the state. The fix isn't better monitoring. It's monitoring from outside.