When is it "obvious" that it's gone wrong?
I remember reading about (but cannot find) a principle that said: after UI, partner is not allowed to use the UI until "it is obvious that something has gone wrong". Having had a few rulings recently that covered this area, I started to wonder if there is any guidance as to "when it becomes obvious". An impossible cue bid or Blackwood response might be such a time, but what about others?
Suppose partner opens a weak 2, pass from opponents and I bid 2NT (we play Ogust). Partner fails to alert and passes. Now next opponent doubles. Can I take it out? Can I redouble (SOS)? Pass is anti-system, but if partner had alerted and passed I would probably leave it in (possibly thinking partner had misbid). When do I get the right to convert back to my partner's major? If opponents now find their suit, can I compete?