Floor plan?

So my gut tells me the same throughout but that might change when you post the pics.

I think I would want the whole staircase to match. Whether that means wood to match the main floor or carpet to match the upper depends on how well the carpet compliments the wood. If the carpet color goes well with the wood, I'd go with carpet. I don't mean carpet that matches the floor but just carpet that looks pretty next to the wood. Some people find carpeted stairs easier to use and less noisy if you have people/kids running up and down.

"Unfortunately I can’t share as I don’t have designer's permission."

If you've paid for plans, and you must have if you're building, your designer sold the rights to you.

"If you've paid for plans, and you must have if you're building, your designer sold the rights to you."

No, that is not how it works. Usually the rights are retained by the designer unless the rights are expressly sold.

Stair finishes normally are the same from one floor to the next. There are always exceptions, and the difference between 'okay' and 'odd' can be a very fine line. I would say the image in your ideabook of the carpeted stair coming down to a hardwood landing then continuing on with hardwood treads looks odd to me; but sometimes function trumps aesthetics.

A contract is a good place to clear up any misconceptions.

I would agree that Alison can't build another home without paying again, but to deny access to drawings and specifications for advice is clearly not what the agreement intended.

I do not know the content of their agreement. I assume the designer owns the rights to the design and the OP respects the designer's right to use images of the design in any way they see fit, and it is agreed to by the two parties concerned in the agreement, exercising its intent.

Perhaps a sketch of the stair's configuration would be sufficient.

Have your five year old son submit his sketch (wink wink nudge nudge).

Alison if in the future you decide you want to switch from carpet to hardwood on the staircase, it will be very difficult to do. Also for resale, hardwood is definitely more desirable on a staircase

As good as the drawing is . . . the image of the stairs will still be helpful.

If you choose carpet, I would definitely not do glass rail. Those two just don’t seem to mesh to me at all. And yes, entire staircase same material.

I missed the glass rail part. I don't see that carpet with a glass railing. I could see tile with a glass railing, LVP with a glass railing, wood of course, or maybe a very flat weave contemporary carpet, but not that.