The broader question that prompted me to ask this is: is such behavior a universally good idea? I have no opinion from my side. I don't recall it ever bothering me. Perhaps there's the performance/security consideration of checking unforeseen keys? I wouldn't mind about that either given that I can remove extraneous keys at the edges (with some or other approach - there are a few)

yes, it exists, although s/keys is really deprecated in favor of schema/select in spec 2

but there is also the notion of closed spec checking which limits things somewhat (and plumbing to add other such options during checking)

> yes, it exists, although s/keys is really deprecated in favor of schema/select in spec 2 So it also exists when using select in a vanilla fashion, right?

I think so? can't remember