Cardiff made the Ospreys work so hard for a URC play-off spot as they pushed them all the way in a thrilling Judgement Day clash.
In the end, the Ospreys claimed the bonus point victory they needed to progress to the quarter-finals where they will be away to Munster next weekend.
But the men from the Arms Park contributed hugely to a thoroughly entertaining nine-try encounter at the Cardiff City Stadium.
There were two touchdowns for them from Mason Grady, with fellow wings Theo Cabango and Gabe Hamer-Webb also crossing.
It meant they picked up two points, taking their tally of bonus points from defeats this season up to a remarkable 11.
Needing four tries, with other results having gone their way, the play-off chasing Ospreys made an ideal start as they opened the scoring after just six minutes with a touchdown from departing prop Nicky Smith.
Following a series of forward carries, the Leicester-bound loosehead dived over from close range, with fly-half Dan Edwards adding the conversion.
But Cardiff quickly responded with a superb finish from Cabango, who had been drafted into the starting line-up after Josh Adams picked up a groin problem in training.
It was a well constructed attack, with Tinus de Beer looping around Ben Thomas in midfield and releasing Cabango.
Then it was over to the flying winger, who produced a double in-out before pinning his ears back for the corner, with the best part of the score yet to come.
Despite being turned onto his back in a tackle from Keelan Giles, he managed to keep his feet in the air and out of touch, while stretching back to get the ball down one-handed.
It really was some finish and the kind of effort that would surely put him in the frame for the Wales squad for the summer Test series.
But just a few minutes later, fate intervened in devastating fashion.
Slipping on the surface, Cabango appeared to damage his hamstring and had to be helped off the field.
Sport can be so cruel at times.
As the half progressed, it was the Ospreys who went back in front on 30 minutes with a late contender for one of the tries of the season.
The attack was launched from inside his own half by full-back by Max Nagy who made some 30 metres, with Wales flanker Jac Morgan maintaining the momentum as he spun out of contact.
Then when the ball was moved left, wing Giles weaved through before feeding Edwards who gave a pass out of the back door to Justin Tipuric, with the openside taking the ball one-handed to finish in the corner.
Cardiff then came close when Grady won the race to Cam Winnett’s kick through, but was unable to get downward pressure on the ball.
Yet the wing was not to be denied for long as his team delivered their own special score just before the break.
The build-up was patience personified as they went through 11 phases, moving the ball from one touchline to the other and back again.
Then came the clinical conclusion, with Winnett throwing out a long ball to Evan Lloyd on the left, with the hooker offloading in the tackle to Ben Thomas who was brought down just short but popped up the scoring pass to Grady.
That made it 12-12 at the end of an enthralling first half.
On the resumption, the pendulum swung back in favour of the Ospreys as they restored their lead with a second try from prop Smith.
It was something of a carbon copy of his first as he forced his way over following another passage of close-quarter carrying from his pals.
To make matters worse for Cardiff, they were reduced to 14 men with lock Ben Donnell being yellow carded for an offence in the build up to the score, as he paid the price for multiple infringements from his team.
Despite this, they managed to cut the deficit through a penalty from Thomas, making it 19-15 going into the final quarter.
Thomas had taken over the goal-kicking duties with De Beer having left the field amid a back-line reshuffle.
Then, on 63 minutes, came the moment the Ospreys fans had been dreaming about.
After sustained pressure, they attacked off a strong scrum, with Morgan Morris picking up and feeding Reuben Morgan-Williams who threw out a long pass for wing Luke Morgan to touch down in the right corner.
That was try number four and it was now a case of them seeing the game out to complete the bonus point win.
But Cardiff weren’t about to lie down for them.
Back they came with a try from replacement wing Gabe Hamer-Webb after great hands from the excellent Ben Thomas, who slotted the conversion from wide out to reduce the gap to four points with ten minutes to go.
But then replacement second row Seb Davies was red carded for a dangerous tackle, which was followed by a penalty try for the Ospreys off a maul drive, leading to a yellow card for fellow lock Rory Thornton.
However, the 13-men had the final word as Grady claimed his second try in the final play. What a game.