Who prophesied that the kingdom would be torn from Solomon?

Answer: Ahijah

Ahijah the prophet tore his new cloak into twelve pieces, prophesying the division.

“During that time, the prophet Ahijah the Shilonite met Jeroboam on the road as he was going out of Jerusalem. Now Ahijah had wrapped himself in a new cloak, and the two of them were alone in the open field.”— 1 Kings 11:29 (BSB)