River AI, a startup co-founded by former xAI leader Igor Babuschkin, has raised $1.1 billion across seed and Series A rounds, the company said August 11, in one of the largest early-stage AI raises this year.

General Catalyst and AMP PBC led the round, with strategic backing from Nvidia and AMD Ventures and additional participation from Y Combinator and Temasek, according to River’s own announcement.

Babuschkin co-founded xAI in 2023 after roles at Google DeepMind and OpenAI, where he worked on the AlphaCode coding system. He left xAI — since folded into SpaceX and renamed SpaceXAI — to start River AI, which only came out of stealth in June.

The company frames itself as a rebuttal to how most people use AI today. “AI should be open, freely available, and affordable,” Babuschkin said in the funding announcement. “It should feel like it is working for the person using it, not the lab that trained it.”

An API for training, not just prompting

River’s first product, the River API, lets developers and companies fine-tune open-weight models ranging from 35 billion to roughly 1 trillion parameters using LoRA adaptation and reinforcement learning, rather than simply prompting a closed model they don’t control. The company says enterprise customers can complete complex reinforcement-learning runs in 15 to 20 minutes without a dedicated infrastructure team, at roughly two to four times the cost savings of closed-source alternatives. Pricing is based on tokens used for training and inference.

General Catalyst CEO Hemant Taneja said Babuschkin’s team has “experience to execute at speed across the entire AI stack,” while managing director Marc Bhargava said River “helps any company build models on their own data, tailored to how they actually work.”

The raise is one of the largest rounds of the year for a two-month-old startup, continuing a pattern of AI labs attracting outsized capital before shipping a mature product — as when Anthropic signed a $10 billion compute deal with the months-old startup Volta. It also echoes the pace of Babuschkin’s former company: SpaceXAI, the renamed xAI, recently launched Grok 4.6 for long-running agent tasks.

River has not disclosed a valuation, though several outlets tracking the round put it near $5 billion.