What is this on the exterior, stucco?

Looks interior. There are available trim pieces for that gap.

Interior. Would you think the trim piece would be standard? I realize there’s no way to know for sure but I can’t imagine this being an acceptable finished product. Thanks a lot.

Did you ask the company installing the windows about the gap? Or if they have any trim that can be glued into place to cover it?

That’s the next step.

What brand windows?

If you are talking about the area in red, that is part of the extrusion in this case. Most manufacturers have some sort of cover that goes in there to clean up that look at you don't usually see those on picture windows. More so on double hungs and other type operators.

I think the OP is talking about debris, bugs, etc so it has to be the gap on the exterior, not the interior. It looks like the exterior wall finish overlaps the window frame.

Well then if that is the case GN, the op needs to get us better pictures of the area in question as I took it to mean the interior as well.

Without anything further to clarify, these are probably picture windows made with the same frame as nearby operating windows (casement, double hung, glider etc.) so that the profiles align.

That was my thoughts as well East Bay, and kind of why I was curious about the brand.

The photo is really confusing and taken at the worst time of day with the shadow virtually concealing all of the interior detailing...