[JonnyQuest]

Unfamiliar, but good partner, though little discussion.

In the following auction, what is 4NT?

1♦ - 1♠
3♦ - 3♥ -- (creates a 100% Game-Force)
4♦ - 4NT

[HardVector]

So, here is what you know. Partner has a good hand with diamonds, doesn't have 3 spades or 4 hearts and doesn't have a club control worthy of bidding 3n. The real question is, is 4d forcing? If you can pass 4d, then 4n is keycard. If you can't pass 4d, then 4n is to play.

[Vampyr]

That is the question though — what is a 100% game force? Is it forcing past 3NT, ie to 5m?

[Tramticket]

Definitely ace-asking. Partner has set diamonds as trumps and is looking for higher things.

Vampyr, on 2019-April-24, 23:03, said:

what is a 100% game force? Is it forcing past 3NT, ie to 5m?

I am a simple person, The opening post used the qualifier "100%" (in bold font) to describe the 3♥ bid as Game Forcing - and you haven't reached game. Why would 4♦ be anything other than forcing? :}

[helene_t]

"To play" is not possible, imho. If you want to play 4nt now you should have bid 3nt before.

[alok c]

1♦-3♦-4♦ sets the trump,even willing to play against void.As Helen says for 4nt to play,he would have bid 3nt earlier.Imo it is RKCB.

[Spielstich]

Slam bidding.
Because 3♥ would risk otherwise to miss the last halt to 3NT if opener holds no ♣stop like here.
The other possibilitiy would be that the responder bids with

♠Axxxx
♥Kxxx
♦x
♣QJx

3♥instead of 3NT in the hope P has 3♠ or 4♥ and finally corrects it to 4NT - what no P can understand.
As ♦ bidder I would not assume that P misbids and assume RCKB.

[P_Marlowe]

Key Card, the only other option is, that 4D was interpreted as Key Card,
and 4NT is the answer.

[jdulmage]

Key Card

[mikeh]

I think the issue is more nuanced than most of the posters, so far, appear (to me, perhaps wrongly) to think it is.

Partner jumped in diamonds. There are some who hold that partner cannot hold 4 hearts and jump to 3D, thinking that the values needed for the jump are equivalent to the low end of the values needed to reverse. If one has the values to bid 3D, with 4H and 6D, one has the values to bid 2H instead.

This has much going for it, as a matter of theory, since using 3H over 3D as an effort to find a 4-4 fit is inefficient (it is far better to use it as a probe...either for 3N or to elicit a spade preference, or perhaps as a pre-cursor to a slam move).

If one accepts this notion, then 3H might be natural but doesn't promise to be. It is merely a force.

Next question: would a raise of 3D to 4D be forcing? In an established partnership this would be an important factor in determining what 4N meant, but we are playing in a partnership where we have not had that discussion, and it would be foolish to bid 4D over 3D, with slam interest, when it might be passed.

So: we bid 3H and partner bid 4D. This denies spade preference, and denies a club stopper, else either 3S or 3N.

If we now bid 4N, natural, we presumably have stoppers, including in clubs. Partner's 3D call is limited. Yes, it is a good hand, but it will be roughly 15-17 hcp with 6 good diamonds: it is not unlimited, and 3D was not forcing in any way.

So why did we not bid 3N?????

On the other hand, we have bid 3H and learned nothing more than 'no spade preference and no club stopper' and now we want to keycard? Why didn't we keycard the round before?

A useful rule is that if one could have bid keycard the round earlier, and partner has provided zero more useful information, we don't keycard now. This takes discipline.

To me, the logical interpretation of this auction is that 4N is natural but forward-going. It can be passed, but it strongly encourages opener to bid again.

With a signoff in NT, responder should have bid 3N last time.

With keycard, responder should have keycarded last time.

So it is neither, and what is left? Invitational to slam.

I would not do this with anyone whose game I did not respect, and even then I'd be prepared to be wrong, in terms of deducing what partner intended. He, too, must infer something about how I will think when he makes the call.

Note that in a coherent method, it is possible to eliminate most ambiguities. Play 4D as forcing, and the need for keycard pretty much disappears, since when opener has no club stopper, he will definitely have a cuebid in a major over 4D, and now responder's 4N is unambiguously keycard. Use kickback, and one can jump to 4H over 3D as keycard, and leave a jump to 4N over 3D as invitational, with all side suits stopped.

However, we are in the land of guessing: not merely what this 'should mean', in a perfect world, but what does partner think I will take it as? This gets deep into spy v spy regressive thinking, but for me, a useful default is 'if it can be natural, it is natural'. So I opt for natural but too strong for 3N over 3D, so opener is to bid with a max and pass (or bid 5D) with a min.

[mikeh]

helene_t, on 2019-April-25, 07:40, said:

"To play" is not possible, imho. If you want to play 4nt now you should have bid 3nt before.

And, of course, if one wanted to bid keycard now, one should have bid keycard the round before...it is not as if opener cuebid a suit where we were worried about our holding for keycard.

[MatthiasK]

Finally, a sensible analysis.