Racing 92 survived a second-half comeback from Connacht to clinch a 26-22 victory in their Heineken Champions Cup opener in Paris.
Tries from Georges-Henri Colombe, Kurtley Beale and Donovan Taofifenua put Racing in control before a deserved Connacht score from Matt Healy.
Racing led 19-8 at the break and a Dominic Bird try extended the lead.
Back came Connacht with Alex Wootton and Conor Oliver tries, but last year's finalists held on in a tense finale.
Connacht's build-up was hit by three players being ruled out through Covid-19 but they made a strong start at the Paris La Defense Arena.
However, the hosts soaked up the pressure before launching clinical attacks with Colombe rumbling over from the first of Racing's excellent driving mauls on six minutes.
Beale stretches advantage
Maxime Machenaud added the conversion and Jack Carty got Connacht on the scoreboard with a penalty before Beale collected a pass from Virimi Vakatawa and sprinted in for a converted try after 17 minutes.
It looked bleak for Connacht when Taofifenua added the third with a wonderful leap and touchdown in the corner as he was tackled.
Teddy Iribaren missed the conversion and Connacht finally got a reward for their sterling efforts just before half-time as Carty's cross-field kick picked out Healy and he collected before going in for a converted try.
Vakatawa raced in for what he thought was another Racing try but the TMO spotted a knock-on and it was ruled out.
The bonus point finally arrived on 51 minutes as Racing's driving maul from a line-out took Bird over the line and Iribaren converted.
Racing were bossing the game but as they pushed for another try Wootton intercepted and ran almost the full length of the pitch to bring Connacht back in it after 62 minutes.
Carty converted and Racing had another try ruled out - Beale missing out because of a forward pass - before replacement Oliver barged over with four minutes left.
With the extras added it became a four-point game and a Connacht infringement, as they pressed for a winning try, concluded a dramatic game.
Racing 92: Beale; Thomas, Vakatawa, Chavancy (capt.), Taofifenua; Russell, Iribaren; Ben Arous, Chat, Colombe, Le Roux, Bird, Lauret, Chouzenoux, Sanconnie.
Replacements: Le Guen, Gogichashvili, Gomes Sa, Ryan, Diallo, Machenaud, Gibert, Zebo.
Connacht: Porch; Wootton, Arnold, Daly, Healy; Carty, Marmion; Buckley, Heffernan, Bealham, E Masterson, Dillane, S Masterson, Butler (capt.), Boyle.
Replacements: Delahunt, Duggan, Aungier, Prendergast, Oliver, Blade, Aki, O'Halloran.