Inferact raises $150M seed round to scale the vLLM inference engine

Inferact, a San Francisco AI infrastructure startup founded by the people who maintain vLLM, has raised $150 million in seed funding. The round, announced on January 22, 2026, valued the company at $800 million post-money. The investor list includes Andreessen Horowitz and Lightspeed Venture Partners, among others. The pitch is simple: take one of the most widely used open-source tools for running large language models and build a commercial business around it, without closing the source. What Inferact is actually selling vLLM tackles inference efficiency with a technique called PagedAttention. The idea borrows from virtual memory, the trick operating systems use to juggle limited RAM across many programs at once. Instead of reserving large, rigid blocks of memory for each request, the system hands out memory in smaller pages as needed. Less memory sits idle, so the same hardware can serve more requests. The project’s reach is broad. vLLM supports more than 500 model architectures and over 200 hardware accelerators. More than 2,000 contributors have worked on it. Amazon, Meta, and Google all use vLLM in their production systems. Inferact plans to layer paid services on top. Those i...