Rhys Webb came through 40 minutes of rugby as Ospreys stretched their unbeaten Anglo-Welsh Cup record with a hard-fought victory over Bristol at The Brewery Field.
The scrum-half returned to his hometown club to captain the Ospreys after getting a release from Wales' RBS 6 Nations squad, playing the first half of their 20-14 success.
Wales coach Rob Howley released the 28-year-old from the national camp to get more game-time - Webb having just recovered from an ankle injury ahead of next weekend's Championship opener against Italy in Rome.
The home side were indebted to tries from Dafydd Howells and Sam Underhill as they added another victory to successes over Harlequins and the Blues, with outside-half Luke Price kicking 10 points.
Bristol's points came from tries through Max Crumpton and Marc Jones, with Billy Searle kicking two conversions.
Webb was heavily involved as Ospreys made a dramatic start scoring a try after only 54 seconds.
The scrum-half put wing Ben John away up the left and he found useful support from flanker Sam Underhill. When the ball was recycled, centre Joe Thomas sent Howells over - and Price converted.
Ospreys went close to a second try through their forwards but had to make do with a 12th minute Price penalty from 35 metres.
The hosts' poor discipline let them down for much of the first half as referee Dan Jones gave Bristol a series of penalties.
And from a powerful drive from a line-out in the 19th minute, hooker Crumpton crashed over. Searle converted to cut the Ospreys' lead to 10-7.
Bristol went close to taking the lead seven minutes from the interval. Scrum-half Alby Mathewson took a quick tap and Jack Wallace looked certain to go in the right corner before Howells and Underhill bundled him in to touch.
A collapsed scrum in added time at the end of the first half gave Searle a final chance to draw the scores level- but his long-range effort went right of the posts.
The second half was only two minutes before wing John was yellow carded, a victim of his side's mounting penalty count.
The first points of the half did not come until the 23rd minute when some Ospreys momentum in Bristol's 22 earned them a penalty which Price kicked from right in front to make it 13-7.
Seven minutes from time Bristol took the lead for the first time as pressure told on the Ospreys'line. From a drive from a line-out, replacement Marc Jones went over and Searle converted.
However, three minutes later Ospreys went up the other end to restore their lead when Underhill burrowed over, with Price converting