OpenAI co-founder Greg Brockman has consolidated operational power as the company prepares for a prospective IPO and scaling compute infrastructure.

There's a new second-in-command at OpenAI. Greg Brockman, the company's president, has officially taken control of OpenAI's most important and profitable projects after Fidji Simo stepped down Thursday due to chronic illness.

Simo, a former Meta executive and ex-CEO of Instacart, served as OpenAI's product and business chief for about a year, steering the company's roadmap and helping it scale. Diagnosed with postural orthostatic tachycardia syndrome (POTS) in 2019, she took medical leave in April and announced Thursday that she would transition to a part-time advisory role.

Brockman, an OpenAI co-founder, assumed product responsibilities during Simo's absence and will continue in that capacity. He will oversee OpenAI's ChatGPT product business, go-to-market teams, enterprise teams, and compute initiatives, according to a source familiar with the company's plans. The company doesn't plan to hire a replacement for Simo.

Sarah Friar, OpenAI's finance chief, and Jason Kwon, the company's strategy chief, will report directly to CEO Sam Altman, as will Brockman.

Brockman faces immediate pressure to drive revenue and justify OpenAI's $852 billion valuation as the company prepares for what's expected to be a historic IPO. OpenAI confidentially filed its prospectus with regulators in June but hasn't disclosed a debut date and is reportedly delaying until next year.

The company is intensifying competition from Anthropic, Google, Elon Musk's SpaceX, and a growing array of cheaper open-weight models from China. ChatGPT's market share fell below 50% for the first time in March, according to Sensor Tower, prompting OpenAI to aggressively promote Codex, its AI coding assistant.

Brockman co-founded OpenAI alongside Altman and others, including Musk, in 2015. The two have been close allies—when Altman was briefly removed as CEO in 2023, Brockman quit in solidarity. Both returned within days. "Greg and I are partners in running this company," Altman later wrote. "We have never quite figured out how to communicate that on the org chart, but we will."

Earlier this year, both found themselves at the center of high-profile litigation when Musk sued Brockman, Altman, and OpenAI, alleging they reneged on commitments to keep the lab nonprofit. In May testimony before federal court in Oakland, California, Brockman addressed the startup's early years and disputed Musk's account of events, facing questions about his personal financial ambitions, OpenAI's structure, and Musk's involvement. Musk lost the case after an advisory jury determined he had waited too long to sue—a verdict immediately adopted by the federal judge.

"I think the tech we are developing is transformative," Brockman said from the witness stand. "This is going to be the most important technological shift in human history."