Announcing our $800M Series C to accelerate the shift to open-source AI
Together AI announced an $800 million Series C funding round. Investors named in the announcement include Aramco Ventures, NVIDIA, Vista Equity, General Catalyst, Emergence Capital, SE Ventures, Pegatron, Salesforce Ventures, March Capital, DTCP Growth, Lux Capital, Geodesic, and PSP Partners.
The company said that in addition to the equity capital, it has secured commitments for over 500 MW of compute capacity, to be capitalized independently by its new investors to support expected compute growth in the coming years.
Together AI described itself as a full-stack AI platform for open-source AI, grounded in frontier research and offering inference for AI applications and agents. It said it is trusted by thousands of customers, including Cognition, Decagon, Eleven Labs, Cursor, and Suno.
On production economics, the company said companies deploying agents for tasks such as writing code, resolving customer issues, analyzing documents, and automating workflows are seeing inference demand scale with that work. It said the cost structure of closed frontier LLMs can become unsustainable in production as usage grows, and that open-weights models including DeepSeek, Nemotron, MiniMax, Kimi, and GLM have closed the quality gap with proprietary frontier models while allowing customization and fine-tuning. Together AI said companies building with open models routinely achieve 6x to 20x lower costs while maintaining equal or better performance, and that Decagon reduced its inference costs sixfold after moving to Together AI.
The company pointed to recent research and product work, including FlashAttention-4 for NVIDIA Blackwell, Together Megakernel and together.compile for kernel-level optimization in production workloads, and expanded post-training APIs supporting tool calling, reasoning, and vision-language models. It said it launched the fastest endpoints for leading frontier open-source models and has become one of the largest producers of AI tokens in the world.
Together AI said it is hiring across engineering, research, product, and go-to-market.
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Publisher excerpt
We raised $800M to accelerate the shift to open-source AI. Here's why the economics of closed models don't scale, and what we're building next.