Jaeger chipped in twice as he posted an eight-under-par 63 at Black Desert Resort in Ivins, Utah on Friday to move to 14-under 128, one shot clear of Ben Kohles (64) and Canadian Adam Svensson (69).
Twenty players were still on the course when tour officials suspended play amid failing light.
Among them was Matt McCarty, who was three under for his round and 12 under for the tournament with three holes to go. He was tied for fourth with Harris English (64), Sam Ryder (66) and Sweden's Henrik Norlander (68).
The Black Desert Championship is the first PGA Tour stop played in Utah since 1963 and the newest addition to the FedEx Cup Fall series.
At the end of the fall, players in the top 125 in the points standings will have full status on the PGA Tour for 2025.
That's important for players such as Norlander, who was No.131 entering the week, and Ryder, who was No.132.
The field's lone Australian, veteran Aaron Baddeley, was set to miss the cut after posting a 74 to be two over as he battles for a 2025 tour card, having entered the event 159th in the standings.
Jaeger's 63 matched the lowest round of the day. He made nine birdies and just one bogey, and he concluded his round with birdies at Nos. 14, 15, 16 and 18. He chipped in from the rough for a birdie at the par-3 15th.
Jaeger, 35, does not need to worry about keeping his card for next season.
He won the Houston Open in March for his first career PGA Tour title, made the FedEx Cup playoffs and finished inside the top 50 in points.
"The two chip-ins on the back kind of made this round from being good to great, so super happy with it," Jaeger said. "Game feels nice."
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