Ulster defence coach Jonny Bell has immediately left the club by mutual consent to pursue a career outside of rugby.
Harlequins have signed former academy product Kieran Treadwell from Ulster ahead of next season.
It was in early December when RugbyPass reported that Ulster were likely to win the race to retain Stockdale, who had been sounded out by Racing 92 and Lyon about a switch to the Top 14.
Northampton Saints No 8 Juarno Augustus is set to leave Franklin's Gardens at the end of the season after signing a three-year deal with United Rugby Championship outfit Ulster.
Former Ireland tighthead prop Marty Moore has announced his immediate retirement from professional rugby to prioritise his mental well-being.
Ireland and Ulster centre Stuart McCloskey has signed a contract extension with his province, keeping him at the Kingspan Stadium until 2027.
The forward enjoyed a productive season with his country on the HSBC SVNS circuit and was then involved in a sixth-place finish at the Paris Games.
England U20s may have won the ultimate prize but Ireland's young conveyor belt of talent shows no sign of grinding to a halt
Two points up at the break, Mark Mapletoft’s side took a firm grip on the previously frenetic exchanges and the second period became a slow death for the Irish.