Expensive fly screen failed on the cat - is that a defect?

Yes, of course that's normal. Brutal cats break everything. Even the €7,000 Rolf Benz sofa actually gets scratches when the cat extends its claws – no complaint helps, no matter how high-quality the material is.

Yes, that's correct, I had also expressed myself poorly in the wording. My plan was not to call the outfitter and complain. ;)
I was rather wondering if it is normal that the stretched net is extremely fine/thin and tears very quickly.
I was in the room when it happened. The cat did not intend to break it. It just stood up on it once and probably extended its claws briefly to "hold on." When we said "no," it got down again. Without any audible scratching. I am quite surprised that this caused damage to the material.
My question was therefore more aimed at: Did the outfitter install cheap discount nets for €500? Should we feel cheated in this regard? Or is it normal that even the nets from the professional are so thin and easily damaged?

Ontopic: You can always try. ;) Would possibly try to negotiate a cheaper reupholstering due to consulting errors - cat mentioned during the sales conversation? - Possibly the mesh solution in the area of destruction?

Offtopic:

Even the €7,000 Rolf Benz sofa actually gets scratches,

As soon as the house is finished, we also want to finally look for a cat at the animal shelter to "bring some life into the place."

So far, I have only had bad experiences with cats and sofas (fabric upholstery). Are there any tips on how to make that somewhat compatible?

In general, the topic of cat flaps is deeply contradictory in KFW houses. Will I really always have to get up later and let the meowing cat in and out?

My question was more aimed at: Did the supplier install cheap discount nets for 500€? Should we feel cheated in that regard? Or is it normal that even the nets from the professional are so thin and easily breakable?

I consider the price for a window and a door from a specialist dealer to be reasonable. That fits. And those from the specialist dealer really have a completely different quality than what you usually get. Ours have been hanging in the windows for many years without any problems and still look like new, apart from the dust...

The problem is that especially the more expensive mesh fabrics are extremely fine in order to interfere as little as possible with the view. And if a 5kg cat jumps against the net, even metal threads probably won't help anymore...

And if a 5kg tomcat jumps against the net, metal threads probably won’t help anymore ...

Visually, gauze is always smooth and looks neat,
a stainless steel net immediately gets dents, and you can clearly see them because of the light reflections.
Regarding quality specialist retailer vs discount store (had both in the old house),
the one from the specialist retailer survived a fall from the 1st floor to the terrace without damage.

As soon as the house is built, we finally want to look for a cat at the animal shelter to "bring some life into the place."

So far, I've only had bad experiences with cats and sofas (fabric cover). Are there any tips on how to make that somewhat compatible?

Give up the sofa ;) (+ Wort4 + Wort5)

My cats can even climb up our fly screens. They have been doing that since they have existed (about 6 years). There are smaller holes in them by now, but you can only find them by searching and they neither affect function nor appearance.