AIBU to not mention another job I've applied for, in a second interview?

[cuspish]

I have a second interview for a 4 days a week job on Monday. It's a job I would definitely like, but I am also waiting to hear about another role that I'd prefer. I'll hear about that in 6 weeks.

If I get the role I'd prefer I'd be working three days, so wouldn't be able to do the first job. Unless they could offer a job share.

If they ask me in the interview about my availability, AIBU to not mention that I've got another role I'm waiting to hear from?

and if so then how do I ask them if they'd be amenable to a job share without telling them why?

No, you definitely don’t mention it. It makes you come across as potentially uncommitted.

If you are offered both, you bring it up in negotiations before you firmly accept either.

but i feel like I'd be lying by omission

It’s not a job share if it’s one person and two jobs. It's two part time jobs. Both employers won’t really care about each other.

You need to go for what suits you best. I’d continue with the first rule, and if you get the second role, you’d need to resign from the first.

If you mean you’d want to find a job share partner for the first role, you’ll need to check their policy. Some places require you to have a job share partner, so you can make an application together. It’s often not the employer’s responsibility to find someone to work with you. Often it’s too much bother, and they’ll go with someone else who can work the pattern they need.

Oh.... and they’d normally think nothing of playing you off against someone else, so don’t feel guilty. You’re not lying. If they ask you a direct question about being considered for another role, then be honest.
They haven’t asked you many other questions, so don’t answer what they haven’t asked!
Good luck. :)

Sorry didn't explain clearly.

I meant that I could potentially do both jobs if the 4 day a week one let me work 2 days with a job share partner.

Then tell them you are waiting for a better offer, but you’re very honourable and would hate to lie by omission!

Have you got a job share partner? You may need to have one.

You don’t have the other job right now. So when they ask at interview about your availability you tell them truthfully you are available.

If by the time they make an offer your position has changed that’s fine.

Think of it like online dating. Right now you’re chatting with two potential suitors. You don’t need to explicitly say that to either, they’ll assume there’s competition because you’re out there looking. Once one of them asks if you want to be exclusive then you have to decide, but you don’t shut down the chatting stage with A because B has a better profile picture.

no i don't have a job share partner. It's a very small company, only 4 people. I'm pretty sure though I could find one. But if I did would they need to reinterview? Or wouldn't they just offer it to the unsuccessful candidates?

You really do need to check their jobshare policy - we can’t answer specific questions without knowing that detail.