I wold take it to the ends of the lower cabinets, since the ostensible purpose is to protect the wall from cooking spills/splashes. Thus, it goes with the lower cabinets and not the uppers.

Stop along with the upper cabinets i disagree with Mrs s it will look wrong

Ideally your uppers should meet the edge of your lowers

You could also not have a back splash

End the backsplash at the end of the upper cabinets. It looks silly to have it end with the lowers and have that square hanging out

End at the end of the uppers.

Am I correct there is no sink or stove on this wall? Why do you need a backsplash here? Why not leave it painted?

Painted.

The backsplash belongs to the counters, not the wall cabinets. Not always perfect, as you can see from your own set up; but better than stopping midway on a counter because the upper cabinet did not match the lower one.

Post a pic of the whole layout and I agree if no range or sink on that wall maybe just paint but no context gets guesses IMO the little angled cabinet should not have been included

I would stop it after the end of the wall cabinets.

It looks like it’s going to be beautiful. What tiles are in contention for the backsplash?

Nice kitchen! The side with the window, where the stove and sink will go, gets a backsplash. The other side of the kitchen would look better with just paint, as others have said. Solves your original problem and saves you money!

Backsplash even with the lower cabinets. Tile all the way up the wall. Or "cap" the tile beyond the uppers with a floating shelf on each end.

With the upper cabinets or no backsplash would look better.

Run it up to the uppers

After seeing pics, splash on sink stove wall and for sure no splash here. Problem solved!

What splash are you using for the sink and stove wall? Nice space so far.

I'd be inclined to remove that small side cabinet and then the upper and lower cabinets would align and you could put the backsplash between the upper and lower cabinets

Agree with no tile here, just paint.