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In a nusach Ashkenaz heicha kedusha, does the chazzan finish kedusha with l'dor vador or atah kadosh?
To be clear, I'm asking about the chazzan, when lechatchila doing a heicha kedusha. Not about an individual who comes in late and I davens along with the chazzan.
I used to daven in a minyan that always used a heicha kedusha and they said l'dor vador. However, i was discussing it with my father over Shabbat and he said that he saw somewhere that you're supposed to say atah kadosh.
I see reasoning for both sides. It serves as the chazarat hashatz and kedusha is said, so follow the normal formula. It also serves as the chazzan's personal Shmoneh Esrei, so he should follow the normal formula.
What do sources say about this?