How would you handle this?

[Ignis Fatuus]

Don't tell Agent A ANYTHING about Client B, other that that you have an alternative offer.

WPS.

Not ANYTHING. Agents are good at using whatever little things you say, even conversationally, to guess what and where the role is. And if you're not going through them, their interest is putting someone else in. That's instead of you.

Don't hesitate to tell him simply that you can't tell him anything about it.

[SimonMac]

Agent A might have only sent two people, doesn't mean that they are the only agent so if you are thinking its a 50/50 chance I'd thinking again.

The question you should be asking is "Is Contract B acceptable in terms or rate and location" as there is no Contract A at the moment.

[Barley]

Sometimes it can take days / weeks for a positive interview decision to be conveyed. Client A could be waiting for final management approval, having to jump through a couple of extra budget hoops etc.

Aternatively you may not have got the role, so id agree witht he bird in the hand...

As others have said, youve a few days pending final contract approval but id say better to take what's on offer unless role A is really worth the risk and you can afford to wait it out.