Per KSU B-25, auctions are "exactly as if a major had been bid" (I take this to be
as if the auction had gone 1m-(pass)-1M) but with an exception for opener
rebidding 1M on 3 trump and no stop in the overcall suit. Thus, opener's rebid is
1NT despite the lack of a heart stop. 2D from opener would be forcing and
opener would be stuck if responder bid 3C. The partnership is unlikely to play
in diamonds if opener rebids 2D, since responder's 3D rebid would be strong.
Since holding 34xx with no heart stop, opener would have rebid 1S, opener
must either have a 4-card club suit or a heart stop for the 1NT rebid. Lacking
a heart stop, responder can rebid 2C (4+ trump, constructive) in this context),
or 3C (4+ trump, forcing). Because opener has denied 5+ spades, 2D
cannot have its normal KSU meaning, and I am going to suggest 4+
diamonds, forcing in its place.
Fred.
On Monday, April 4, 2022 at 1:56:23 AM UTC-4 chuck swart wrote: