[jahol]

Sometimes, it happens that you think too much at bridge table....and after minutes and minutes....you still make a very bad decision (making partner cry something like "I would prefer you NOT to think at all". From point of view of your partner, the situation is trivial....from your point of view....it is not....or is it??May be yes....

You have
A9xxx---Qx---AQ9---10xx.
Opponents nonvulnerable, you vulnerable, your LHO opens the bidding with 1 club, your partner 1 spade, RHO double, you 4 spades (you may not agree with this bid, but I am not going to discuss it). A bit surprising 5 clubs call from LHO is passed back to you and you double. You partner leads spade Q and this is the dummy (once more, this is not discussion about the bidding)

K10x---J10xxxx---K8x---9x.

Spade Q is covered with K and A and ruffed. After some thinking, the declarer plays small diamond to ten, king and ace. What do you play?

[jahol]

The dummy was

K10X--J10xxx--K8x--9x.

I apologize for the mistake.

Jahol

[FrancesHinden]

I cannot see any reason not to play a trump (if declarer runs it holding AKQJ8xx then so be it).

But I'm definitely missing something somewhere because it's unlikely that a spade is going to cost either, dummy not being replete with entries.