Mikel Oyarzabal scored twice, including one from a penalty, before Portu and Alexander Isak rounded off an impressive victory after Rafa Mir had briefly pulled Huesca level.
La Real go one point above Real Madrid, although having played one game more than the reigning champion, and also become the first team to hold onto top spot for two consecutive rounds this season.
Imanol Alguacil's side was in the mix for a Champions League qualification place last season, only for its form to fizzle out at the restart of play from the three-month break due to the coronavirus pandemic.
Sociedad has hit top form again in recent weeks, with only one defeat from its opening seven games and new signing David Silva showing against Huesca what an asset he could be for its bid for the top four.
Silva laid on two assists before being replaced late on.
Earlier, Villarreal missed the chance to go top after being held to a goalless draw by Cadiz, which sustained momentum from its 1-0 win over Real Madrid last weekend, to be fifth.
Granada continued its excellent start by moving up to third with a 1-0 victory away at Getafe.