Cheptegei and Jacob Kiplimo saw their team tactics take a dent when Martin Magengo Kiprotich fell off the pace early on.
Aregawi and Kejelcha again increased the rhythm through the halfway stage, the main pack now cut to 15.
Barega was back at the helm with 10 laps to run, Canada’s Mohammed Ahmed and Kenya’s Benard Kibet muscling their way through to sit on Kejelcha’s shoulder.
As Cheptegei and Fisher made their way up through a bunching pack, Kejelcha was again on hand to offer a spurt of acceleration.
Into the last kilometre, Aregawi took up the running, but the race promised a pulsating finish as the pack of 12 all clung on.
Just before the bell rang for the final 400 metres, Cheptegei surged to the front and the race to the line was on.
Ahmed followed and Fisher fell off the pace, but made a remarkable recovery to medal.
There was no coup de grace for Barega, however, as Cheptegei held on for victory in the first medal event at France’s national stadium.
Barega eventually finished seventh in 26:44.48, one spot behind Kejelcha, with Ahmed taking fourth and Kibet fifth.
Joshua Cheptegei of Uganda celebrates after winning the men’s 10,000-metre final [David J Phillip/AP]
USA set new world record in 4×400 mixed relay
Earlier on the purple track, the USA broke their own world record in the 4×400 mixed relay in the opening heats, crossing the line in three minutes 7.41 seconds amid a party atmosphere.
They set the previous mark of 3:08.80 at the 2023 World Championships in Budapest.
Team USA led midway through the second lap in a textbook performance, overcoming a fast field in the opening heat in which four national records were broken as well as the world mark.
“I always knew we were going to run fast, and we talked about how it was going to take a record to win a medal,” said American Shamier Little. “It took a record to win our prelim.”
The French team were willed across the finish by a partisan home crowd, as they held off Belgium (3:10.74) and Jamaica (3:11.06) to finish second in 3:10.60 in the rarely contested event.
The crowd had to be shushed as they chanted for the French team on the first day of the athletics programme at the Stade de France and they broke into a loud roar as France took a slender lead.
Little pulled ahead for the US, however, and Bryce Deadmon extended the lead.
The Americans were eager to avoid the drama of three years ago, when they were disqualified from the Olympic final – and later reinstated due to an official’s error – before eventually claiming bronze.
Paris 2024 Olympics – Athletics – 4 x 400m Relay Mixed Round 1 – Stade de France, Saint-Denis, France – August 02, 2024. Kaylyn Brown of United States, Bryce Deadmon of United States, Shamier Little of United States and Vernon Norwood of United States pose with a time board as they celebrate after setting a new world record and winning heat.