Brad Lightcap, OpenAI chief operating officer, during a live recording of “Hard Fork” at the SFJAZZ Center in San Francisco, June 24, 2025. (Mike Kai Chen/The New York Times)Brad Lightcap, a longtime OpenAI executive, said Tuesday that he was leaving the company after eight years to start a new venture, the latest in a string of departures from the artificial intelligence startup. Lightcap offered little detail about the new venture. He joined OpenAI in 2018 and had become its chief financial officer before being appointed chief operating officer in 2022. “It is bittersweet to share that I’ll be moving on from OpenAI to start something new,” he wrote in a note to employees that he also posted on social media.