[Knurdler]

I know the standard rule that a new suit by responder is forcing eg 1♦ 1♥ is forcing for 1 round.

I am fairly sure that if opener rebids 1NT, then a new suit by responder is not forcing eg 1♦ 1♥ 1NT 2♣.
The reason I have read for this is that opener has limited their hand.

I have read that if opener repeats their suit and responder bids a new suit that is a 1 round force eg 1♦ 1♥ 2♦ 2♣
Is this sequence forcing? Why? The opener has limited their hand.

[steve2005]

Opener has limited his hand with their rebid but responder is still unlimited unless you are playing strong jump shifts.
Even playing strong jump shifts, you need to be able to force while offering choice of games or to invite.
After 1♦-1♥-1NT
you need to be able to check back to see if opener has 3 hearts to play in 4♥ if you have a 5-3 fit.
The normal way to do this is to artificially bid the unbid minor as new minor forcing.
New minor forcing can also be used when you are interested in slam and need a forcing bid.
There are other ways that are more advanced.

[bluenikki]

Knurdler, on 2026-August-31, 11:36, said:

I know the standard rule that a new suit by responder is forcing eg 1♦ 1♥ is forcing for 1 round.

I am fairly sure that if opener rebids 1NT, then a new suit by responder is not forcing eg 1♦ 1♥ 1NT 2♣.
The reason I have read for this is that opener has limited their hand.

I have read that if opener repeats their suit and responder bids a new suit that is a 1 round force eg 1♦ 1♥ 2♦ 2♣
Is this sequence forcing? Why? The opener has limited their hand.

Opener _should_ have limited their hand. I don't think you can rely on it with a partner you don't know well. But I don't think that is relevant to your question.

To me the question is _why_ do you want to make a nonforcing bid in a new suit?

Is it because you misfit opener's suit? That is a very bad reason.

Is it because you will get a better score in one of your suits than in theirs? That is true only if you make your contract, and you often won't. Indeed, I'm inclined to think you usually won't.

[DavidKok]

You are focusing too much on 'limiting the hand'. Even a limited hand can be very interesting! What's more, a hand being limited doesn't just make bidding to the right partscore attractive, it also makes passing attractive. On balance, it's not a good use of bidding space to now pivot to responder's choice of partscore.

On the example sequence 1♦-1♥; 2♦-? you need to notice something very important. Opener has denied holding a balanced hand (1NT), heart support (2♥), a spade suit (1♠) or a club suit (2♣). Even if responder has short diamonds, that strain is usually going to be best. Introducing clubs now with 3♣ as an offer to play is a really bad idea - opener already denied holding clubs, and you're raising the bidding by a level. It takes a very special hand to want to retreat to clubs here, and building a system around very special hands isn't winning bridge. What's more, on most of the hearts-clubs two-suiters where it might be interesting to run to a different partscore, the opponents have a spade fit. Count your lucky stars they aren't in this auction.

[Kaitlyn S]

Knurdler, on 2026-August-31, 11:36, said:

I know the standard rule that a new suit by responder is forcing eg 1♦ 1♥ is forcing for 1 round.

I am fairly sure that if opener rebids 1NT, then a new suit by responder is not forcing eg 1♦ 1♥ 1NT 2♣.
The reason I have read for this is that opener has limited their hand.

I have read that if opener repeats their suit and responder bids a new suit that is a 1 round force eg 1♦ 1♥ 2♦ 2♣
Is this sequence forcing? Why? The opener has limited their hand.

I think you meant 3 clubs since 2 clubs is insufficient. But for sake of argument, let's assume you are talking about the two level and change the auction to 1C-1H-2C-2D. You might wonder why 2D might be forcing?
Let's argue your side for a moment and say that 2D can be passed. 2D might be a good call on xxx KQxxx QJTxx --. Indeed you would be sad to have to pass 2C on this hand and kudos concerning your bridge knowledge if you also are uncomfortable with 2H, also nonforcing. I like that to show six hearts and at IMPs I might pass 2C sometimes with six hearts.
You're not going to hold that hand very often and in most cases passing 2C with a minimum (and on rare occasion correcting to 2H with looooong hearts) works out okay.
Now, let's see the case for 2D forcing.
1. Partner might be looking for three card heart support for his/her five card suit for game level, or perhaps to invite game.
2. Partner might be looking for a spade stopper to play notrump.
3. Partner might be trying to show shape to find the best game or slam.
If 2D is nonforcing, partner would have to bid 3D on each of these, which may rob the partnership of the room needed to find the best contract.