Art's UI thread got me thinking about this hand we played in Philly in a bottom bracket KO. It's mostly funny. Spots are random and please ignore that N has a submin opening, I really don't remember the whole hand at all because I played like I was drunk that entire day. Partner and teammates will confirm this fact.
I was S, partner was N. Here's the auction as I heard it (Assume explanations are for bids as they are made)
2+ ♦ limited ........................ natural forcing 1 round w ♣
unbal w 5+ ♦ or 4=4=4=1 ............. GF w ♦ support, asks shortness
♥ shortness ......................... RKC for ♦
0 or 3 KC .............................. Signoff
3 KC plus stiff K in ♥ .............. SIGNOFF
Unfortunately this is not what partner heard:
2+ ♦ limited ........................ natural forcing 1 round w ♣
unbal w 5+ ♦ or 4=4=4=1 ............. GF w ♦ support, asks hand type
♣ shortness, suitable for NT ........ RKC in clubs (Partner's logic: with ♦ I can safely bid 3♦ first)
0 or 3 KC .............................. Asks for ♦K, grand try
Denies ♦K, shows ♥K (???) ........ Impossible call, auction is off the rails*
* 6♦ is impossible because partner already "knows" we don't have the ♦K, so for him to ask in ♦ again implies he must have it, in which case why didn't he just bid 5♥ in the first place, asking for the ♥K, unless I'm masterminding?
At the 4♠ call, E (for no apparent reason, once again, bottom bracket KO) stopped to ask what our bidding meant throughout the auction, and all the miscommunication came to light. We finish the auction, go down 1 in 6♦ (I really don't remember the actual hands but partner played it well to only go down 1) and we lose imps vs 3NT making.
Discussing this afterwards partner and I agreed that the auction went hella off the rails and that partner's interpretation of the auction up through 4♠ is right and I was wrong. We both thought we did our best to ignore UI from each other during the discussion of the auction. This did bring up other questions.
Partner thought it was possible that he had AI at 5♦ that the auction had gone off the rails and/or that 5♦ might be the last making contract, and therefore he might be able to pass 5♦. I'm not sure of his logic for this. He maybe thought his hand was so bad that I've just clearly taken him for the wrong number of KCs, or something, or he's just decided his hand is so misfitting that he wanted to slow down. Or maybe he just wanted to convince himself that we could salvage a result from this, I dunno, but I'm glad he decided to bid on from an ethical standpoint, I guess.
That said, I don't understand his 5♥ bid if the hands are how I remember them, if we are actually on the same wavelength, since to him my bidding up through 5♦ is also consistent with something like Ax, -, AQxx, AKQJxxx (making 7 opposite a min like Kxx, KQxx, Kxxxx, x or xxx, AKxx, KJxxx, x but only 50% opposite KQx, KQxx, J10xxx, x). I really don't remember the exact hands so I don't know if partner SHOULD have bid 7 or not, but maybe he also thought that with a hand like that, why would I bother showing a diamond fit? So maybe he woke up later trying to recall why I showed a diamond fit, and therefore ♦ was a viable playing point? I dunno. I also don't want to make it seem like I'm targeting my partner because it's possible that his hand was different and 5♥ was somehow a reasonable call.
tl;dr? Start here.
Anyhow, I guess my question is this: if partner has AI that the auction is off the rails and 5♦ might be a good stopping point even though 5♦ is technically a forcing bid on his interpretation of the auction, can he pass a) if there's no UI and b) if there is UI from the opponents asking questions. I know the answer to a, I suppose, but b is more complicated?
AND, if our opponent (who had no intention of ever bidding) had never asked any questions, partner might have passed 5♦, so hilariously our opponent generated UI which constrained us to bid on.