Ulster took over at the top of the Pro12 table with a 22-17 win at Glasgow Warriors on a night when Jonathan Sexton made his presence felt on his Leinster comeback in a 31-19 victory over previous leaders Ospreys.
Talismanic fly-half Sexton, making his first appearance of the season after recovering from a shoulder injury, scored a first-half try followed a penalty try and a Josh van der Flier score as Leinster led 24-0 at half-time.
Van der Flier went over for a second time and Sexton took his tally to 16 points before he was sent to the sin-bin for a high tackle.
Ben John, Dafydd Howells and James King dotted down for Ospreys, but the visitors slipped to a first defeat of the season in captain Alun Wyn Jones' 200th appearance for the region.
Ulster took advantage of Ospreys' first slip-up, coming out on top in a gripping contest at Scotstoun to make it four wins out of four.
Paddy Jackson finished a magnificent move following a turnover from Ulster in their own 22, with Louis Ludik making the break and the fly-half finishing and adding the extras with just under 20 minutes remaining.
Finn Russell scored seven points with the boot on his 24th birthday in his first appearance of the season after recovering from a head injury, but the Warriors fell short
Benetton Treviso claimed their first win of the season, getting the better of Newport Dragons 27-11.