Dead spot in lawn

thats gonna be some sort of a bug type issue, if it was fungi you would see water type grass in the area like dollar weeds.

but to test, turn part of the ground over to check it, if its fungus the roots under the grass will be white or gray looking

Last year I noticed a dead spot that was almost a perfect circle. It was maybe 4ft across. I didn't do anything about it but noticed it got a little bigger. It's now maybe 10 ft but seems less like an organized shape. I don't know if that's just a coincidence that it started as almost a perfect circle. It seems bigger now than at the end of summer last year, probably at least double in size.

Of part of the dead area?

This is from a section that still has a little green left but mostly dead

There’s some drought stress from what it looks like.

Can you easily lift the sod out of the ground or do you have to pull pretty hard? If it’s grubworms the dead grass should come up without any work.

How is the soil in that area?

My builder brought in a bunch of red clay and so the roots stayed shallow and cooked when the summer heat hit.

Can you easily sink a screw driver into it or is it compacted?

Ronk is the expert but if it were me I’d cover the following bases:
-apply insecticide if it lifts easily
-apply fungicide and ensure the grass is getting 1.5” of total water a week applied in the morning over 2-3 days
-rake up the dead grass and top dress with a .5”-1” of mixed topsoil, peat moss and sand. You can then replug or sod any large dead areas or let it spread if you have some grass left and are patient.

If you want we can dive further to see what the issue is. Do you remember the month it started? What month did it stop spreading? We’re the borders discolored?

I said it wasn’t a fungus because you said it started last year,, went throughout the summer, and got bigger this year. That’s not how a fungus acts. But if it started in the spring and then started again this spring then that is more fungal like.