Saint Roi came from last to first to open his account over fences in the Brand New Racing Post App Novice Chase at Leopardstown.
Fourth in the Irish Champion Hurdle, the Champion Hurdle at Cheltenham and the Punchestown Champion Hurdle last season, the JP McManus-owned seven-year-old had found the reopposing Fil Dor four lengths too strong on his chasing debut at Navan last month.
The pair again dominated the betting, with Fil Dor the 8-11 favourite to confirm his superiority and Saint Roi a 3-1 shot for Willie Mullins and Mark Walsh.
Visionarian gave a bold sight in front for much of the Grade One contest, with a couple of jumping mistakes late in the back straight putting Fil Dor on the back foot.
Walsh, meanwhile, bided his time aboard Saint Roi before producing him to challenge for the lead approaching the final fence.
Visionarian, the 25-1 rank outsider, did his best to make a race of it, but Saint Roi's class kicked in on the level and he proved two and a quarter lengths too strong in the end.
Speaking to RTÉ Sport, Mullins insisted that a shift in tactics proved crucial in delivering victory.
"The change of tactics worked fantastic," he said.
"(Saint Roi) was a Grade One hurdler but just not good enough for the championship races I think and we schooled him over fences last year and then he got a setback and we put him back over hurdles and this year he was going well over fences.
"So I asked JP (McManus) did he mind if he went jumping and he said 'no problem, let's have a go', competing the first day but the change of tactics made all the difference.
"I know it was bold coming here having his second run over fences in a Grade One but I thought I'd rather race for 70-plus thousand than go for a beginner's chase and it paid off thankfully. Mark was very good on him."
Walsh added his satisfaction that Saint Roi was able to stay poised in position to capitalise when Fil Dor, with Jack Kennedy aboard, made a mistake.
"Fences have settled him down. He's very good, very clever and I knew Jack was in trouble, he made a mistake at the third last - the ditch - so I just had to kick on to the last and make sure I got a good jump," he said.
"Everything went to plan for me so when it goes to plan it's great and it's great to get a winner on the first day. It just takes a bit of pressure off for the rest of the week."
Additional reporting: PA