What should each eval case record about where it came from?

Each case should record where it came from and when, at minimum: the trace or session id it was pulled from, who confirmed the expected behavior, be it a person or a review process, and the date it was captured. None of that changes what the case tests, but all of it determines whether you can still trust the case a year from now.

Without a source trace, there’s no way back to the original context if the expected behavior ever looks wrong. Without a capture date, there’s no way to tell a case that still matches current behavior from one written against a version of the agent that no longer exists. Provenance is what turns a fixed set of cases into one you can maintain instead of one you eventually have to throw out and rebuild from scratch.