River AI, a two-month-old startup founded by xAI co-founder Igor Babuschkin, has raised $1.1 billion in a seed/Series A round led by General Catalyst and AMP PBC, with participation from Nvidia, AMD Ventures, Y Combinator, and Temasek2,3,4. The company emerged from stealth in June with a mission to rebuild the AI stack from the ground up, focusing on personally trainable assistants rather than human worker replacements5.
The capital was received over two rounds, according to River AI's funding announcement. The company declined to comment on its valuation.
Babuschkin previously worked on generative modeling and reinforcement learning at Google DeepMind and led large-scale training at OpenAI before co-founding xAI. In a launch blog post, he wrote: "To get there, we believe the stack has to be rebuilt end to end: training, models, the product layer, and new hardware that lets personal AI live close to you".
River AI's first product is an API that allows developers to fine-tune open models using reinforcement learning (RL) and low-rank adaptation (LoRA). The company positions this as an alternative to prompt engineering, with product literature stating: "Prompting steers a model you don't own and can't improve. River lets you train open models into ones that are truly yours".
River AI said its API allows enterprises to perform complex reinforcement-learning training runs in 15 to 20 minutes without a dedicated infrastructure team and is two to four times more cost-effective than closed-source alternatives. The API is billed per one million tokens, with rates dependent on the open model used.
The company's thesis is that enterprise AI will shift from reliance on general-purpose models from large labs toward companies customizing and owning their own models using open-weight architectures. Babuschkin's vision extends beyond enterprise tooling: "Capable agents will be a normal part of everyday life. Less like the assistants you call on today when you need a task done, more like guardian angels: quietly present, on your side, helping with what actually matters to you. They will know you well, and they will be yours, not someone else's," he wrote.
AMP PBC, one of the round's co-leads, is an AI-focused investment firm founded in 2026 by former Andreessen Horowitz general partner Anjney Midha, who backed companies including Black Forest Labs, Mistral AI, LMArena, and OpenRouter while at a16z.
ANALYSIS The round's size — $1.1 billion at the seed/Series A stage for a company that emerged from stealth roughly two months ago — places River AI among the largest early-stage AI raises on record. The investor mix spanning a generalist venture firm, a dedicated AI fund, two chip manufacturers, an accelerator, and a sovereign wealth fund reflects broad institutional interest in the open-model fine-tuning layer. River AI's bet on open-weight customization rather than proprietary foundation models positions it as infrastructure for enterprises that want model ownership, a distinct lane from the closed-API approach offered by frontier labs.