Kostecki joined the famous Ford team on a multi-year deal last season, which should have meant his spot was safe for the 2023 season.
However within days of the season finale in Adelaide last December there was fevered speculation that his seat was under threat.
That speculation linked a squabble with rival driver Scott Pye at the Supercars Gala Awards to Kostecki's impending exit.
The split between Tickford and Kosteck is now official, the team issuing a brief statement today.
"Tickford Racing and driver Jake Kostecki have decided to part ways by mutual agreement and will not continue with their partnership in the 2023 Supercars Championship season," the statement read.
"Tickford wishes Jake well in his future endeavours.
"The team will make further comment on its 2023 driver line up in due course."
Kostecki's seat will go to 2022 Super2 champion Declan Fraser, who had been set to miss out on a promotion to the main game until this late silly season twist.
Interestingly, Fraser has seemingly beaten Tickford's own Super2 star Zak Best to the seat, with Best known to have looked to find a promotion for 2023.
At that point it was expected that he would run a wildcard programme with Tickford as well as forming part of the eight-driver enduro line-up.
