Complete speculation: you could instruct Claude to hide one random mistake in every document.

And Claude should write down the mistake in a sealed envelope, so it doesn't make into the database.

A review that doesn't find the mistake counts as invalid.

This is what bag scanners at airports do - the hit rate is so low and the job so boring the software projects fake contraband onto the imagery. Fail to spot the knuckledusters and expect a chat with the manager.

You could do this for code reviews. Have Claude include one subtle bug into each PR. If the reviewer does not spot it, then the PR is not mergable.