[ArcLight]

Assuming you have an agreement that you can raise responders major with just 3 cards, when do you do so?

If you open a minor and responder bids a major, when will you raise pards major when holding 3 cards, as opposed to making a different bid?

I was under the impression that if you have a balanced hand, bid 1NT. With some kind of shape you might raise pards major.

[awm]

My general rules for this are:

(1) With four spades, I will always rebid 1♠ in preference to raising hearts on three.
(2) With substantial extras I will do something else (like reverse or jump rebid or bid Gazilli if playing that).
(3) With 5/4 in the minors and minimum I will virtually always raise on three.
(4) With a 6-card minor and min, I will raise on three any time I think a 4-3 major fit will be better than a 6-1 minor fit. This is usually, but not on a very robust suit.
(5) With a balanced minimum, I will not raise with 4333 shape, but will otherwise usually raise unless my hand seems very "notrumpy" (i.e. lots of slow cards, scattered values).

[whereagles]

My rules are:

- Must have a min (11-14)
- Must be unbalanced
- Must have a singleton
- Can bypass spades with 4351/4315
- With 6331 or 7321 opener has a choice

Most won't agree with the underlined.

[Yu18772]

3 posts bellow yours there is a detailed discussion about a particular type of such auction by awm http://www.bridgebas...1h-uncontested/
As you can see - there are a lot of different opinions, ranging from people who raise almost always to those who never and every flavor in between, this is also much dependent on you other agreements.
Most people dont bypass spades, and seem to have some requirements about honor position, this seem to be pretty representative of of all the auctions of this type. You will also find major regional differences between US and Europe in the approach. Doesnt mean one is better - it is more about what would your p expect than what is right in general.
Personally my p and I raise on 3 cards only if no other legitimate bit is available, and the 3 in major are at least KJx. When playing with new partners I explicitly ask not to raise on 3 unless absolutely necessary.

[Free]

For me:
- never with a 4 card ♠ after 1m-1♥
- 3 card suit with a top honor (preferably)
- a reason to do so (singleton, weak doubleton,...)
- other bids aren't attractive (poor 6 card suit, 1NT with weak doubleton OM, Gazzilli - really!)

Some examples
- after 1♣-1♠:
Axx-x-AKx-Jxxxxx
Kxx-xx-Axx-AJxxx

- after 1♦-1♥:
xx-Qxx-AQxx-KQxx
x-Kxx-AJxxx-KJxx (with max I would bid 2♣ to raise afterwards)

- after 1♥-1♠:
Kxx-AQxxx-x-KQxx (alternative is bidding 2♣ Gazzilli, but when partner bids 2♦ we have to rebid 2♥ or drop dead in 2♥ in a 5-2 fit when p is minimum)