Writing analysis for Common Games provides me with Real Deals (after they are played, of course). This was from 2025:

Vul:E-W Dlr: East	Q9 K75 AJ1096 KQ7
J872 64 542 A986		1053 1083 K73 J532
	AK64 AQJ92 Q8 104

After East's pass, what should South open? I teach that with 15-17 balanced and a 5-card major, open 1NT. Is this balanced? Not really, although it is considered "semi-balanced." Typically, with a side 4-card suit, something like:

AQ1087

43

AQ76

K4,

I say to open 1 because there is no rebid problem (after a 1NT response, 2 is not a lie). But in my write-up of the actual Common Game deal, I showed a 1NT opening! Why? Because after 1-1NT, there is no good rebid. Too much to pass and not enough for a 2 reverse or 2NT. Rebidding in a 2-card suit is not for me.

After 1NT, North could use Pupper Conventional response to notrump to ask about majors Stayman or try showing diamonds, but I prefer the quantitative (invitational) 4NT as shown. With 16 and a nice 5-card suit (not to mention a good 4-card suit as well), South accepts the invitation. The jump to 6 should show a 5-card suit; North is happy to play in the 5-3 fit.

If West hits on a diamond lead, declarer would be suspicious (who would lead from a king) and might fear a singleton and go up with the ace, but that would be tantamount to giving up. Say declarer finesses and it loses to the king. Would East know which black ace his partner has? Just a guess, and the contract will make if East doesn't find a club switch. What about on a non-diamond lead?

Now declarer has a 2-for-1. He can try clubs first. If the king loses to the ace, the diamond finesse still gives a chance. Here, with the A right, declarer can throw a diamond on a club and try to trump a spade in dummy. Lots of work, but +980 will be a great result.

If North (or West) dealt, North's 1NT opening might lead to North declaring. In that case, if declarer plays as above, no lead can set the contract.