By Alex Tresniowski
June 22, 2009 12:00 PM

Finally, evidence that things have gotten really messy between Brad Pitt and Angelina Jolie: On June 5 Brad showed up on the Long Island set of Angelina’s thriller Salt for a belated celebration—she’d turned 34 one day before. After joining the crew in a chorus of “Happy Birthday,” he “took one of the little birthday cakes and smushed it in her face,” says a source. “It was really funny.” Two days later, the pair were by each other’s sides again at Salt‘s New York City wrap party, says the source.

This hardly sounds like a couple on the brink of a breakup, as months of breathless tabloid reports have suggested. Brad’s get-together with ex Jennifer Aniston? Separate bedrooms? Talks with lawyers? The stars told PEOPLE through a rep that the headlines are “not true,” and that they are as committed as ever to their children—Maddox, 7, Pax, 5, Zahara, 4, Shiloh, 3, and twins Vivienne and Knox, 11 months.

What’s fanned the gossip? The pair have rarely been snapped out together in recent months. But away from the cameras, a friend says there’s been plenty of couple time at their rented estate on Long Island. While Angelina filmed Salt, Brad frequently dropped by the set with the children. On their last visit, “the kids brought their dog,” says the set source. If there was friction between the pair, neither showed it. “There has been no tension,” says the source.

While Angelina worked, Brad ran the kids to school and to the local Carvel ice cream parlor. In May Angelina joined Brad in Cannes for the premiere of his film Inglourious Basterds. At the afterparty, she teased him for bonding with the boys. “Angelina looks at us and traces the shape of a heart, like, ‘Ahh, what a sweet bromance,'” says Brad’s bud and Basterds costar Eli Roth. The night before at Michelangelo restaurant, the couple “were holding hands, and kissed on the steps,” says restaurant manager Mikael Mammoliti. “I could tell they are very close.”

After Jolie’s birthday, Pitt stopped by the Salt set again, this time in Washington, D.C., on June 8, before zipping off to Switzerland for the Art Basel show. It’s a hectic lifestyle, but somehow, says a colleague, “they make it work.” And that means remembering the special days: For Mother’s Day, Brad gave Angelina inscribed jewelry. So those rumors? A friend says pay them no mind: “They are very, very happy.”