Together AI closes $800M Series C at $8.3B valuation as open-source inference demand surges

Together AI, a San Francisco-based infrastructure platform for deploying open-source models at scale, closed an $800 million Series C at an $8.3 billion post-money valuation, nearly 2.5x its $3.3 billion Series B valuation from February 2025. The round was led by Saudi Arabia's Aramco Ventures and included participation from NVIDIA, Vista Equity Partners, General Catalyst, Emergence Capital, and others. The raise brings Together's total funding to $1.3 billion across four rounds since its 2023 seed founding.

Together AI reported over $1.15 billion in annual recurring bookings last quarter, driven by demand from companies seeking cost-effective alternatives to frontier-model APIs. Customers including Cursor, Cognition, and Decagon are running production workloads on open models (DeepSeek, Nemotron, MiniMax, Kimi) instead of closed alternatives, with reported cost savings ranging from 6x to 60x for comparable or better performance. Open-source model usage across the industry has tripled year-over-year, signaling a structural shift in inference economics.

The valuation jump and investor roster reflect confidence in open-source inference as a durable market. Together plans to scale its infrastructure footprint roughly 50-fold over the next five years, betting that compute capacity, not model ownership, drives sustainable value. For architects and infrastructure teams, this signals ongoing margin compression on proprietary APIs, accelerating adoption of open-weight alternatives and raising the bar for frontier-lab pricing power on routine inference tasks.