How I Shrunk My Agent's Core from 15 to 9: Why Hit Rate Alone Can't Tell You Which Rules to Retire

I almost deleted 29 rules from my agent's governance system.

Their hit rates sat near zero. Some hadn't fired across dozens of sessions. By every metric I had, they were dead weight — rules that consumed context budget without ever intercepting a mistake.

One script stopped me. It asked a different question than my dashboard did: not "did the rule fire?" but "can the rule fire?"

Twenty-nine detectors were broken. The rules weren't useless. They were running blind — looking for the wrong command, a deprecated tool name, a signal that had changed format months ago.

That near-miss is about signal quality, not about which rules I eventually demoted. Separately, I restructured my Core layer from 15 rules to 9 — seven demoted, one promoted, six slots freed. The hard part wasn't the restructuring. It was figuring out which retirement signals I could trust.