Fox has previously been signed to one-year deals exclusively during his six years at the Swans, joining the club after a successful stint in the VFL for Coburg.
He was delisted and later re-listed as a rookie in 2020 but has since picked up form, finding himself entrenched in Sydney's best 22 since Round 11 this year.
Fox produced a brilliant performance in Sydney's 22-point win over defending premiers Melbourne on the weekend, punctuated by a smother that catapulted his name into the headlines.
“The urgency to get back, it was a great piece of play. They just got back hard and did the job and defended the goal line – you can‘t ask much more than that.” Sydney coach John Longmire said about Fox post-game.