Connacht went through 28 phases in search of a last-gasp try but Leinster held out to clinch an engrossing 21-18 derby victory in the Guinness PRO14.
Max Deegan, one of Leinster's two try-scorers, won a decisive penalty at the breakdown -- right at the death -- as Leo Cullen's men maintained their record of not losing a regular season home PRO14 match since February 2015.
Connacht, with the wind at their backs in the first half, recovered from Deegan's try to lead 13-11 at the interval, with their strong finish to the first half including prop Finlay Bealham's converted try.
Jonathan Sexton and Luke McGrath inspired a 10-point surge from Leinster, with the latter crossing on the hour mark, and despite a terrific Matt Healy try in response, Connacht's relentless efforts were only enough for a losing bonus point.
Playing with the advantage of a very strong wind, Jack Carty's right boot gave Connacht the lead inside two minutes. Sexton, Leinster's captain for the day, levelled matters four minutes later.
Andrew Porter did brilliantly to disrupt a dangerous Connacht maul and while Dan Leavy completed the turnover, the visitors were soon pressing again before a costly John Muldoon penalty ruined some promising approach play.
Rob Kearney was next to threaten, following up on McGrath's break, and although Leavy was then held up, a subsequent scrum penalty saw Sexton make it 6-3.
Sexton then combined brilliantly with home debutant James Lowe to almost set McGrath free, and a few phases later, the Ireland talisman was only a pass away from sending flanker Leavy over.
That elusive first try arrived when winger Lowe's superb reverse pass -- in a one-two with Noel Reid -- teed up Deegan for an unconverted score in the right corner on the half hour.
Connacht centres Tom Farrell and Bundee Aki increased their influence in the lead up to Carty's second penalty, and the latter two combined in a free-flowing 37th-minute attack which ended with tighthead Bealham muscling over. Carty converted for a two-point lead.
A long-range 49th-minute penalty from Sexton edged the hosts back in front, and with more of referee Ben Whitehouse's decisions going Leinster's way, the home side had the platform to push ahead.
A Lowe-inspired attack had them on the cusp of a try before they turned a missed touchfinder from Carty into a crucial seven-pointer.
Kearney, Fergus McFadden and Cronin kick-started a prolonged spell of attacking and McGrath, stretching out of a tackle, supplied the finishing touches for Sexton to convert.
Back came Connacht, their skipper Muldoon and Ultan Dillane going close before Healy wrong-footed both McFadden and Sexton to raid in from the left wing. McFadden was fortunate to be still on the pitch after previously taking out Tiernan O'Halloran in the air.
The gap remained at three points as fly-half Carty missed the conversion on the near side, and he also failed to find touch from a late penalty. Connacht regrouped for one final push but Leinster's robust defence held them at bay.