I think nuclear winter is a fake invented by cold war propaganda. If tomorrow we detonate all nukes available, the amount of dust in the atmosphere won’t even approach a large volcanic eruption.

Volcanic eruptions occasionally inject literally cubic kilometres of stuff high into the atmosphere. That’s insufficient to cause a global winter, only a year without a summer: https://en.wikipedia.org/wiki/Year_Without_a_Summer

I believe it would kill most humans, but all, no.

Humans don’t need AI to do that temperature.

And we’ve already exploded many hundreds of nuclear weapons and no nuclear winter.