I've got Safari set to open "All windows from last session", but recently, the two most recent iterations of Safari, I think, it's been opening to an empty page.

I've successfully trashed /Users/artie/Library/Preferences/com.apple.Safari.plist, and the first time I quit/launched Safari the pref worked, but since then...nada.

Anybody else?

Just curious: what happens if you select History > “Reopen All Windows from Last Session”?

That was a good, thought provoking question.

"Reopen..." is greyed out, presumably because I've got Cookie set to clear history when I quit Safari, but I've had that setting for years, and it's never kept my windows from reopening.

I'm going to check how far back my archived versions of Cookie go, and maybe I"ll learn something.

Yep! That was, indeed, an excellent question; thanks for pointing me in the right direction.

To make a long story short, I tracked the problem down to a SafariRestore (extension) pref that had come unstuck. (I don't know about others, but once I install something and set its prefs, much of what I've done/learned escapes out the back door.)

I couldn’t have predicted this particular outcome, but I’m glad you figured out what florfed Safari’s works.