Tech
The Engineer Who Built Colossus Is Now Building for Bezos
Kyle Kosic, the xAI co-founder who assembled a 200,000-GPU supercluster in Memphis, left OpenAI in early April for Jeff Bezos's Project Prometheus, a physical-world AI lab that has raised $6.2 billion and is seeking $100 billion from sovereign wealth funds.
The Financial Times reported on April 7 that Kyle Kosic, a co-founder of xAI and former OpenAI engineer, had left OpenAI to join Project Prometheus, Jeff Bezos's secretive AI startup. No departure announcement preceded it; the confirmation came through FT's reporting on Prometheus's growing technical roster.
At xAI, Kosic led the infrastructure team that put 100,000 Nvidia H100s online in Memphis in 122 days, then doubled the cluster to 200,000 in another 92. Colossus was, at commissioning, the largest AI training system ever assembled. His public technical record contains no papers, patents, or indexed commits; what is documented is the cluster. At OpenAI, where he first joined in April 2021 and worked on infrastructure powering the company's largest training runs, he was recruited by Musk to co-found xAI in May 2023, returned to OpenAI in May 2024 as a Member of Technical Staff in Technical Operations, and left again this April.
The departure from OpenAI is a meaningful subtraction in a small population. Engineers who have assembled a frontier-scale GPU cluster from power contracts to cooling to delivery schedules are a handful globally. OpenAI is in the middle of Stargate, the $500 billion infrastructure commitment with SoftBank and Oracle to build American data centers, and its broader technical organization was already thinning: multiple senior exits through 2025 and a triple leadership departure in April 2026 alone. xAI's founding cohort, the eleven researchers who co-founded the lab in May 2023, has scattered entirely by the same deadline: Christian Szegedy in February 2025; Tony Wu, Jimmy Ba, Toby Pohlen, Zihang Dai, and Guodong Zhang through late February and March 2026 after SpaceX acquired xAI; Manuel Kroiss and Ross Nordeen by the end of March. Kosic had been the first to leave, exiting for OpenAI in May 2024 before the acquisition closed.
Bezos and Vikram Bajaj launched Prometheus in November 2025 with $6.2 billion. Bajaj holds an MIT physical-chemistry PhD and helped launch Google Life Sciences in 2013 as its first chief scientific officer, later rebranded Verily; he left in October 2016. He spent the following eight years at Foresite Capital and its company-creation arm Foresite Labs, then co-founded Xaira Therapeutics, an AI drug-discovery startup, in January 2023, before joining Bezos. Prometheus targets aerospace, chipmaking, and defense with roughly 100 technical staff drawn from OpenAI, Google DeepMind, and Meta, building models trained on sensor data, fabrication logs, and manufacturing operational signals. The lab has sought $100 billion from sovereign wealth funds for an associated manufacturing transformation fund.
The model Colossus was built to train drew partly on distillation from OpenAI outputs, as cross-examination of Musk established in April. The pipeline ran from the incumbent labs through xAI's infrastructure and back out as Grok. Kosic built the hardware that carried it. Prometheus's training corpus is industrial data. The cluster-building discipline is the same.
Bezos now holds AWS, the cloud infrastructure running OpenAI and Anthropic's inference workloads, alongside a physical-world AI lab staffed by the engineer who assembled the most capable training cluster built to date. Prometheus has not announced a close on the $100 billion sovereign wealth fund round. Bezos hired Kosic before it closed.