Igor Babuschkin
About Igor Babuschkin
Igor Babuschkin studied physics at TU Dortmund and did experimental particle physics research on the LHCb experiment at CERN. He then moved into machine learning. He worked as a research engineer at Google DeepMind and was a member of technical staff at OpenAI. He is an equal-contribution co-author of the 2019 Nature paper on AlphaStar, DeepMind's StarCraft II agent.
He co-founded xAI with Elon Musk in 2023 and led its engineering teams as chief engineer until August 13, 2025. In a post on X that day he said he was leaving to launch Babuschkin Ventures.
His X profile lists him as CEO and co-founder of River AI, and PitchBook lists the same role. He is based in the San Francisco Bay Area.
Babuschkin Ventures launched in August 2025. Babuschkin described it as supporting AI safety research and backing startups in AI and agentic systems. PitchBook classes him as an active individual angel investor and counts four investments. We could not confirm the full list from public sources, so only verified deals are named on this page.
His best-documented investment is RadixArk, an AI infrastructure company that grew out of the open-source SGLang inference framework. RadixArk announced a $100M seed round at a $400M valuation on May 5, 2026. Accel led and Spark Capital co-led. Babuschkin took part as an angel alongside other individual investors and strategic backers.
On X he wrote that SGLang is the best inference framework available. He said RadixArk was formed to improve it and to democratize more of the frontier AI stack, and that he was happy to support the team in the round.
Babuschkin's own description of the firm points to AI safety research and to startups building AI and agentic systems. His one documented seed investment is in AI infrastructure. No check size, fund size or preferred stage has been published, so none is stated here.
- RadixArk: open AI infrastructure company built around the SGLang inference framework for training and serving frontier models. He joined its $100M seed round, announced May 5, 2026.
- x.com/ibab/status/2051690211873308892
- x.com/ibab/status/1955741698690322585
- finsmes.com/2026/05/radixark-raises-100m-in-seed-funding.html
- citybiz.co/article/841973/radixark-launches-with-100-million-seed-roun
- cnbc.com/2025/08/13/elon-musks-xai-loses-co-founder-igor-babuschkin-fo
- techcrunch.com/2025/08/13/co-founder-of-elon-musks-xai-departs-the-com
- pitchbook.com/profiles/investor/530051-68
- nextomoro.com/igor-babuschkin
Investing activity
Igor Babuschkin appears in 1 AI deal tracked by the Lounge deals desk, rounds totalling $100M. The rounds are mostly Seed, with a median round size of $100M. The most recent is RadixArk (Seed, $100M, Jan 2026).
Igor Babuschkin most often invests alongside Spark Capital, Accel, AMD and Hock Tan, and the companies they back on Lounge are mostly in AI Infrastructure.
Deals
Frequently asked questions about Igor Babuschkin
Does Igor Babuschkin invest in AI startups?
Yes. He runs Babuschkin Ventures, which backs AI safety research and startups in AI and agentic systems. He was an angel in RadixArk's $100M seed round.
What is Babuschkin Ventures?
It is the investment firm Babuschkin announced in August 2025 after leaving xAI. He said it supports AI safety research and backs AI and agentic-systems startups.
What check size does Igor Babuschkin write?
He has not made his check size public, and we do not estimate it. Founders should not assume a figure.
What stage does Igor Babuschkin invest in?
His documented AI investment is RadixArk's seed round. He has not published a stage focus, so seed is only one data point.
What is Igor Babuschkin's background?
He is a physicist by training and worked at CERN, Google DeepMind and OpenAI. He co-founded xAI in 2023 and led its engineering until August 2025. He is now CEO and co-founder of River AI.
How can founders reach Igor Babuschkin?
His main public channel is X at @ibab, where he posts about his work and investments. We have not verified a LinkedIn profile or a personal site.
Is Igor Babuschkin an angel investor?
Yes. Igor Babuschkin invests personally as an angel.
What AI companies has Igor Babuschkin invested in?
Igor Babuschkin's AI investments include RadixArk. The 1 round on Lounge are listed on this page with amounts, dates and co-investors.
What stage does Igor Babuschkin invest at?
In the rounds tracked on Lounge, Igor Babuschkin has invested at Seed, with a median round of $100M.
Who does Igor Babuschkin co-invest with?
Igor Babuschkin's most frequent co-investors on Lounge are Spark Capital (1 deal), Accel (1 deal), AMD (1 deal), Hock Tan (1 deal) and John Schulman (1 deal).