Jennifer Lawrence previews Phoebe Philo and casual-luxe style

Jennifer Lawrence has spent the second half of September quietly rewriting the rules of celebrity dressing, moving between pared-back streetwear and a preview of a high-fashion collection while promoting her new film. Between mid-September outings and a photocall at the San Sebastian International Film Festival on Sept. 26, the actor showcased a trio of looks that underscore a comfort-first sensibility balanced with deliberate luxury touches.

On Sept. 18 Lawrence reworked a summer staple into a night-out ensemble, according to reports. She paired baggy jeans and a basic black T-shirt with thin black sandals, then layered a luxe black fur shawl that elevated the otherwise simple outfit. Observers noted her alligator Lady Bag by The Row and described a deliberately minimal beauty approach, with a bare manicure contrasted by a darker pedicure that helped carry sandals into cooler weather.

Four days later, on the first day of fall, Lawrence again leaned into relaxed dressing centered on bold color and layering. Accounts agree she built the outfit around bright red track pants with a vertical stripe, a white crewneck T-shirt and a navy knit sweater, tied at the waist with a flannel...