Chances this "mistake" holds up?
 

So I booked a lengthy itinerary through a OW partner. Due to a schedule change, they had to adjust one of my AA legs. In rebooking me, they put me in F (I booked J) on the AA flight. I have selected my seat, meal, etc...How is this likely to play out?

If this is a cash ticket, the question is whether AA accepts the payment tendered for the F ticket. If it does not, there will be an add/collect due from the ticketing carrier and you will be reseated in J if there is J availability at that point. Otherwise in Y.

As long as you've actually been reticketed I'd say you're 99% or better.

If you haven't been reticketed then less than 10%.

re-ticketed, seat selected, only a few days from the flight.

Will do.

If a new ticket has been issued, then I cannot see it likely that you will have any issues

No there won't ; the other airline is the travel agent and is the one that AA would go back to if there was money owing. The passenger is not its customer

Is the AA leg a domestic flight?

I'm curious too as to what flight it is and if F is actually an option, in only a handful of AA international and transcontinental flights offer F....

This happened to me once a while back, albeit it was AA who erroneously rebooked me in F instead of J (this was a transcon with 3 classes of service). Based on my experience, I would say you have a good chance of sitting in F.

Good question.

There actually is an F cabin on pretty much every TCON flight (in fact, all but the smallest aircraft). But, very few with both F & J. Entirely possible that OP is on a 2-class aircraft which was booked on a J fare basis but reflects as a seat in the single premium cabin, which is F.

Perhaps easiest is for OP to provide his routing, date, and flight numbers.

I think the point many are trying to make is that F on an AA domestic flight is rarely true F as on the 321T or 77W, but is called first nonetheless. Thus, OP may be seeing First on the screen, but has been moved to a 2-class aircraft which doesn't have a business cabin.

Well I can’t really think of a scenario where the OP was originally booked in Business, as he said (which means a Transcon if we’re taking domestic), and then a schedule change moved him into a 2-class bird with the front marketed as First class. We’re talking about something like LAX-JFK that was switched to LAX-DFW-JFK, and that just seems unlikely to me. AA would have been more likely to move him to another LAX-JFK flight.

I guess he’s free to come back and clarify so folks can give him more precise advice.