Preview supposed to be the same curse you get in you next escalation run. There are no notification that you are currently on esc run but you should not be able to do astral reset until you completed the stage required per esc run. There's a dialog on esc run completion tho, letting you know that you completed the esc run and may choose to proceed to next esc run.
Mainly changes are the curses and the label on preview should be changed into current. A spell supposed to be locked too. I'll take a look later, haven't checked it since there's not much feedback around esc and challenges.
Edit:
Thanks for catching it, you were right, escalation was broken. Checking the box before an Astral Reset had a bug where it got silently reset to off right before the game checked it, so escalation never actually started. Fixed now, should work as intended next update.