WASHINGTON — President Biden was spending his first state dinner alongside President Emmanuel Macron of France on Thursday when a guest seated at the head table with them turned the conversation toward the merits of American cuisine.

As Mr. Macron and his wife, Brigitte, indulged in a selection of American delicacies, Alexandra Pelosi, the daughter of Speaker Nancy Pelosi, asked Mr. Biden, a man with uncomplicated tastes, what foods his country was best known for.

“He said: ‘Hot dogs, ice cream and spaghetti,’” according to the younger Ms. Pelosi, who was seated next to Mr. Macron. Then her mother chimed in, telling the (somewhat puzzled) French president that she eats a hot dog every day in the cloakroom.

“I had the best seat in the house,” the speaker’s daughter said. “It doesn’t get any better than that.”

That’s probably true.

At the state dinner, held to celebrate the relationship between the United States and France, guests swept past journalists and mingled for a marathon cocktail hour as they waited to be received by the president and Jill Biden, the first lady, and Mr. Macron and his wife, Brigitte.

The lengthy hellos, which were supposed to run about an hour, led to a late evening for the president, who stayed out sipping soda and chatting with Mr. Macron until 12:30 a.m., according to several observers.

Senator Chris Coons, Democrat of Delaware and an ally of the president, said his interactions with both leaders were “warm and positive” and called the experience “a delightful evening where we got to celebrate the best of the Delaware spirit.”

As the two presidents greeted their guests, photos turned into hugs. Hugs turned into chats — and shop talk as Mr. Biden conversed with other Democrats about upcoming legislation and the primary election calendar.

And then all hell threatened to break loose when the bartenders ran out of glassware, depriving some invitees of necessary social lubricant after years spent in a pandemic. That’s when it helps to invite veterans like Terry McAuliffe, a guest and the former governor of Virginia, who estimates he has been to over a dozen of these fetes. He knew to keep close to the bar and enjoy the wait.

“For me, having been a veteran of these, you wait until the end” to jump into a receiving line, Mr. McAuliffe said. He had no complaints. “To see all those different people and have conversations with them — that part could’ve gone on all night.”

At one point, it seemed like it might.

“You have two talkers,” another guest, Mike Barnicle said, about the evening’s host and guest of honor. The revelry led to a late evening for the president, who stayed out well past midnight chatting about topics that included sausages with Mr. Macron, according to several observers. A State Department official said the party lasted until just after 1 a.m.

Since the state dinner itself didn’t appear on plates until 10:30 p.m., some early birds left the party: Mika Brzezinski and Joe Scarborough slipped out shortly after, according to their colleague, Mr. Barnicle. (“Morning Joe” wasn’t going to host itself.) Many of the 300 or so guests arrived home well after 1 a.m., and those without security details were pointed toward a nearby street to hail a cab.

The White House had no immediate comment.

“I think everyone, including our leaders, are a bit tired this morning,” said Ambassador Rufus Gifford, chief of protocol for the United States, in an interview on Friday, shortly after he saw the Macrons off at Joint Base Andrews. Totally worth it, he said.

“For the first state visit of the United States in three years, we wanted to make sure we essentially savored every minute.”

A weekday party that lasts until after midnight is unusual in Official Washington, a stuffy little pocket within a much livelier capital where book parties pass for star-studded events. Embassy soirees — where people like to go to see everyone they already see all the time — are hot tickets. The disciplined citizenry often climb into bed in time to squeeze in a workout or appear on their eponymous morning shows.

No, this is not relatable to the rest of the country, or even to those who operate just beyond the privileged confines of a crowded white tent on the South Lawn.

But the human impulse to gather — particularly after the worst part of a lengthy pandemic — is universal. Officials who planned the event said the need for Mr. Biden and Mr. Macron to project a united front against the Russian invasion of Ukraine was urgent.

“The magnificence of American soft power was on full display,” Mr. Gifford said. “These personal relationships are such the crux of American foreign policy, and that’s why these matter so much.”

Mr. Gifford watched members of the French delegation closely to make sure they were enjoying themselves — and, crucially, the food, which included a selection of American cheeses and triple-cooked butter potatoes.

“The plates were empty, the glasses were empty,” he reported. In other words, none of the French pointed out that the brut rosé and chardonnay on offer was, after all, “American wine,” as the French ambassador did at the state dinner hosted by the Clintons in 1996.

As America’s old alliance was carefully nursed, flashes of bipartisanship that would perhaps surprise the more tribe-minded supporters of lawmakers appeared. Representative Steny H. Hoyer of Maryland, the No. 2 Democrat, approached Rep. Kevin McCarthy, the California Republican who is attempting to become the next House speaker, to shake hands. That happened more than once.

A senior White House official, who spoke anonymously to describe private conversations, said that conversations with Republicans were kept light — talk of sports took the place of more contentious topics including, say, looming oversight investigations. Guests were discouraged from working the room because of protocol reasons, an attendee said, so it became hard to get a good look at who was doing what.

Not impossible, though.

“I actually saw Steve Scalise smile,” said Mr. Barnicle of the Republican Louisiana congressman. Then he delivered a camera-ready analysis: “Last night, at least for a moment in time, they achieved something that the world would love to see in Ukraine: a cease-fire.”

In the cold light of day, the candlelit comity may just have been a moment of calm before attendees return to their post-lame-duck battle positions.

Mr. McCarthy appeared less jovial — “I’m at dinner with my mom,” he told a reporter when asked about his thoughts about attending a dinner with Hunter Biden, the president’s son, whose financial dealings are a prime investigative target of an ascendant Republican House. (Ms. Pelosi did not interact with Mr. McCarthy.)

But for Mr. Biden and Dr. Biden — whose adherence to coronavirus protocols meant that they did not have an inauguration celebration, an Easter egg roll, or a long slate of holiday parties their first year — guests said their interactions had the element of making up for lost time.

The first lady wore a beaded Oscar de la Renta creation, a choice that called back to several successors who favored the designer at heavily photographed moments.

Mr. Biden, who did not enjoy the time he had to spend hemmed in by his Secret Service detail because of coronavirus worries, got a few hours to enjoy the fun part of being a statesman. He spent his evening slinging his arm around guests and chatting with his guest of honor.

The entertainment portion, by Jon Batiste, didn’t start until about an hour after dinner began. Then, as the evening turned into early morning, the musician began asking “the boss” if it was OK to play one more song. The president kept responding with a thumbs-up, according to an attendee in clear view of the president’s reaction.

Patrick Dillon, who attended with his wife, Jennifer O’Malley Dillon, the White House deputy chief of staff, enjoyed spending the evening with a “very diverse, very accomplished crowd.” Mr. Dillon added that “there was also this sense that even in a challenging few years, there’s good and important stuff to celebrate, and it’s needed.”

So as the clock ticked well past midnight, Mr. Batiste, a Louisiana native, called out from the stage and asked others from his home state to get up and dance. He began to weave a path through the tables, stopping to draw others — including his former “Late Show” colleague, Stephen Colbert — out of their seats, according to a senior administration official who watched the end of the program.

Though the morning would hold more negotiations, more meetings, more television hits, there were perks worthy of waiting until the finale. The night closed with a scene that would have been hard for anyone in Washington to fathom just two years ago: Mr. Colbert dancing with the White House press secretary.