[mike777]

How do you gf and later depending on partner's response agree on a trump suit?

1D=1S
(2C or 2D)=?

[Cyberyeti]

Over the rebid of opener's suit, many pairs play some sort of artificial relay, I'd suggest looking up Bourke relays (we play a home hashed version that is inv+, but the original is GF).

Over 2♣ you 4th suit (again we play inv at the 2 level, but most play GF) then set the suit.

[mikeh]

After 1D 1S 2C, 2H is gf. Artificial, fourth suit. That’s pretty standard, though I don’t play this in my main partnership…for various reasons

1D 1S 2D

Here there is ambiguity. Most standard partnerships seem to fumble their way through. One common means is to play 2H as an artificial one round force. I’ve played 2H as a one round force, may turn out to be gf, and 2N as forcing one round with 5+ spades and 4+ hearts. Note that all of this works best if you have an immediate response to 1D to show a less than invitational hand with 5+ spades and 4+ hearts. A lot of players use some form of Meckwell.

[akwoo]

Over 1D-1S-2C, playing 2H as artificial and forcing to game is basically standard.

Over 1D-1S-2D, probably the expert treatment is playing 2H as artificial forcing one round, but the non-expert standard is that 3C is artificial forcing to game.

[johnu]

mike777, on 2025-December-28, 14:15, said:

How do you gf and later depending on partner's response agree on a trump suit?

1D=1S
(2C or 2D)=?

In terms of researching this sequence, look up 4th suit forcing, and 3rd suit forcing.

[P_Marlowe]

Hi,

after 2C, you bid 2H as FSF, raising responders suit later, this showes SI,
regardless of, how strong you play FSF.
after 2D, you bid either 2H as 3rd suit forcing, raising responders suit later,
this showes SI, or if 2H is natural, you use 3C as 3rd suit forcing, ..., due to
the fact that 3C is also a bid on the 3 level, you are in a GF seq.

With kind regards
Marlowe

PS: The above sentence a bit longer explained, but (re)searching is certainly req.,
there are some variations, that are not covered in my sentences.

[Huibertus]

mike777, on 2025-December-28, 14:15, said:

How do you gf and later depending on partner's response agree on a trump suit?

1D=1S
(2C or 2D)=?

There are many potential solutions, some of which you can find in other comments.

What I've done for many years to great satisfaction is to have a 2NT rebid as game forcing, it can include a balanced hand with a 4 card major support. In combination with the agreement a jump rebid to a new suit shows a fragment (implying a splinter in the 4th suit) in an unbalanced hand with a four card support of invitational or stronger strength over this we played 3NT by responding hand as to play.