The Ospreys returned to the top of the Magners League despite having their unbeaten start brought to an end by champions Leinster in Ireland.
Luke Fitzgerald's converted try, after some brilliant interplay with Felipe Contepomi, gave the hosts a narrow 7-6 advantage at half-time.
Two drop-goals from Isa Nacewa then gave Leinster a winning lead.
But the Ospreys claimed a losing bonus point after James Hook converted Nikki Walker's last-minute try.
The Ospreys had the better of the opening period and Hook missed an early chance to give them the lead, sending a drop-goal wide.
Leinster weathered the early storm and looked more creative in attack, but they found themselves behind after 20 minutes.
Lee Byrne was halted just short of the line after a fine run and the ball eventually came to Hook, who succeeded with his second attempt at a drop-goal.
That lead only lasted three minutes though as the sweeping interplay between winger Fitzgerald and Argentine Contepomi saw Fitzgerald go over for a converted try.
The Ospreys quickly cut that lead to a point after Hook kicked a penalty and they really piled on the pressure in search of a try.
They almost got it at the start of the second half when Hook broke and kicked the ball forward, only for Shane Horgan to get his hand to it first.
That woke Leinster up and they started to stretch the Ospreys, with Contepomi putting the hosts 10-6 up with a penalty after 52 minutes.
By now the home side were having the better of the possession but neither side could create any real openings as both defences held up.
Leinster did manage to open up a seven-point gap when Contepomi landed a penalty from in front of the posts.
Replacement prop Cian Healey was then denied a try that would have put the game out of sight after knocking on as he drove over.
But in the last five minutes Nacewa made sure of the win with two drop-goals, before Walker's late converted try secured the losing bonus point which sent the Ospreys back to the top of the table.
Ospreys coach Sean Holley: "We set our stall out and we came away with a bonus point and that's got to be the minimum at away games.
"We were disappointed at half time and felt we could push on and win.
"For long periods we were the better side but we lacked a little bit of clinical edge and perhaps that's what Leinster had."
Leinster: Dempsey; Horgan, O'Driscoll, Contepomi, Fitzgerald; Nacewa, Whitaker; McCormack, Jackman, Wright, Cullen, Toner, Jowitt, O'Brien, Heaslip. Replacements: Kearney for Horgan (62), Healy for McCormack (56), Fogarty for Jackman (69), O'Kelly for Toner (46), S. Keogh for Jowitt (62), Jennings for O'Brien (46). Not Used: Keane.
Ospreys: Byrne; Bowe, D Bishop, A Bishop, Walker; Hook, Webb; D Jones, Bennett, A Jones, Wyn-Jones, Evans, Thomas, Tandy, R Jones. Replacements: Biggar for A Bishop (65), Wells for Webb (53), Shervington for Bennett (62), James for A Jones (53), Gough for Wyn-Jones (57), Tiatia for Tandy (53). Not Used: Vaughton.
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