Previously successful in the showpiece event with Dylan Thomas in 2007 and Found in 2016, the Ballydoyle handler houses the ante-post favourite for this year's renewal in this son of Camelot.
A Group One winner at two in the Vertem Futurity Trophy at Doncaster, Luxembourg looked every inch a potential Derby winner in the making when third in the 2000 Guineas at Newmarket on his return.
But a subsequent injury ultimately led to the three-year-old missing Epsom and he only scrambled home on his return in the Royal Whip Stakes at the Curragh in August.
O'Brien was adamant Luxembourg was nowhere near concert pitch, however, and he found the necessary improvement to provide his trainer with an 11th Irish Champion Stakes success at Leopardstown.
Three weeks later he is set to line up as favourite for Europe's premier middle-distance contest.
"He's good and everything has gone well since Leopardstown. We were delighted with his run and everything has been very good since," said O'Brien.
"We think he's in a good place and when we run we will know. It's not long since he ran, so his work hasn't been too tough, but we're happy with everything he's doing.
"I don't think anybody wants extremes (of ground) and we're the same. I suppose everybody is in the same boat, but hopefully it won't get too bad.
"He won the Futurity Trophy on soft ground and he is by Camelot, who is by Montjeu, so hopefully he'll handle it, but in an ideal world hopefully it's not too soft."
Having missed a good chunk of the season, Luxembourg will head to Paris relatively fresh and lightly-raced following just six lifetime starts.
With a maximum field of 20 virtually guaranteed, hurly burly is a given, but O'Brien believes his charge has the temperament to handle whatever is thrown at him.
"He ran three times last year and has run three times this year, so he's had the six runs, but I think he's usually a very offhanded, straightforward horse," he added.
"He relaxes very well and I'd be happy to come forward out of the gates."
O'Brien will have a second string to his bow in the form of outsider Broome, who was beaten just under 10 lengths into 11th place in last year's renewal.
The six-year-old was thoroughly impressive when opening his account for the current campaign in the Hardwicke Stakes at Royal Ascot in June, since when he has finished fourth in the King George and in a Grade One in America, before finishing last of seven behind Luxembourg at Leopardstown.
O'Brien said: "He ran in America, which probably didn't suit him, but we were very happy with his last run. We were using it as a prep for this race, we think he gets a mile and a half well and likes a big, open track.
"We think he might have found the tracks in America a little bit tight for him as sometimes he can step just a little bit slow from the stalls, especially at Saratoga the last time.
"Hopefully he can run a good race and there are plenty of races left for him in America or Japan or Hong Kong for the rest of the season."