[cvcherry]

First, I don't know when GIB switched to 2/1, I'm not very familiar with 2/1(than sayc). But now the GIB bidding have lots of problems, after this hand I became crazy

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I'm completely shocked when dummy shows only 2♥ so why didn't we play in ♦? It was too lucky that GIB led a club and heart broke 3-3, thus contract made
I've seen a few more hands that GIB didn't have enough trumps to make a rebid - when I move cursor to the bid it showed 5 trumps, so I raised with 3, and I found we were in 4-3 contract

[barmar]

GIB on BBO has always played 2/1.

Maybe you're thinking of the Express Automated Fun tourneys, which started out saying that everyone played SAYC, but recently switched to 2/1. That's because when GIB is subbed in, it plays 2/1, so they decided to make the human system consistent with GIB.

As for bids not having the number of cards promised, that happens often. GIB sometimes goes outside the bidding database when its simulations tell it that there's a better bid. Humans will also soetimes give delayed support with a doubleton honor, although it's usually Qx or better. I also don't understand GIB's jump to the 4 level; it's already shown its values by bidding 2/1 as a passed hand.