[pescetom]

https://www.bridgeba...b|P|mb|P|pc|H5|

After 3♠ (correctly explained as 5+♥ 3+♠) I hover over 4♦ which is the obvious bid, but no, it seems it promises the earth... so I settle for 4♠.
Was 3♠ a 1st level control in hearts in the addled and increasingly expensive brain of GiB here?

[smerriman]

lol, nice. It definitely uses it as a spade raise; it'll bid 3♠ with QJx-QJxxx-x-AKxx too, and if you had bid 4♥ over the top, it'll see that as a cue and force you to 6♠.

But it seems it also temporarily uses it as a control after finding a heart fit.. to be fair, I've seen plenty of humans unsure what suit was agreed in this sequence too But a robot should do better.

[pescetom]

 smerriman, on 2024-June-27, 16:07, said:

to be fair, I've seen plenty of humans unsure what suit was agreed in this sequence too

I was taught that if opener raises the 2/1 response suit, a raise of the opening suit resets trumps and invites a control-bid. I understand that as being the mainstream treatment in this situation too, which has some obvious advantages: no exceptions to remember, we know about the double fit, the spades fit may well be longer and some gadgets work better in spades.

There is nevertheless a case for playing 3♠ here as a control-bid in hearts (or non-serious if you invert things), particularly if your slam investigation style privileges control bidding without RKCB: indeed I do so in one partnership.
But it's not what I would expect a robot to assume and it's not what it explains either.

[1175]

Just out of curiosity, suppose South had jumped to 4NT after 3♠. What suit does the explanation say that North will use for the key-card reply?

[smerriman]

Spades.

[pescetom]

You only asked about the explanation. There is also the question of whether it actually replies 2 keycards in spades or 3 in hearts