Together AI has emerged as the definitive “Acceleration Cloud” for the open-source ecosystem, positioning itself as the primary alternative to the closed “API” model of OpenAI and Google. While competitors rent out access to black-box models, Together AI provides the high-performance infrastructure that allows enterprises to own their intelligence. By 2026, it has become the backbone for companies building on top of Llama, Mistral, and Qwen, offering an inference engine that runs these open-weights models significantly faster and cheaper than standard cloud providers.
The company’s technical edge is rooted in its deep research pedigree—specifically its creation of FlashAttention, an optimization technique now used industry-wide to speed up AI training. This research-first DNA led to the development of Together MoA (Mixture of Agents), a breakthrough architecture released in mid-2025 that layers multiple open-source models together to outperform GPT-4o on complex reasoning benchmarks. With the acquisition of Refuel.ai in 2025, Together AI moved up the stack, offering not just raw compute but also data labeling and transformation services, effectively becoming a full-stack “OS” for the open AI economy.
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Core Technology: FlashAttention & Mixture of Agents
- Together Inference Engine: A proprietary runtime that leverages FlashAttention-3 and custom kernels to run open-source models (like Llama 3.2 and DeepSeek) with lower latency and cost than any hyperscaler.
- Mixture of Agents (MoA): A novel architecture that forces multiple smaller models to collaborate in layers—critiquing and refining each other’s answers—to achieve “frontier-grade” intelligence without the massive cost of a single giant model.
- Instant Clusters: A self-service platform that allows developers to provision massive clusters of NVIDIA H100 and H200 GPUs in minutes, solving the “GPU scarcity” problem for startups.
- Custom Models: A secure fine-tuning pipeline that allows enterprises to train models on their private data within a dedicated Virtual Private Cloud (VPC), ensuring data sovereignty.
Business & Market Status
- Valuation: Valued at approximately $3.3 Billion following a $305 Million Series B round in early 2025 led by General Catalyst and Prosperity7.
- Revenue: Surpassed $300 Million in Annual Recurring Revenue (ARR) by late 2025, driven by the massive migration of enterprises from closed APIs to self-hosted open models.
- Partnerships: A key partner in the NVIDIA Cloud ecosystem, often receiving first access to the newest silicon (like Blackwell GPUs) due to its optimization expertise.
Company Profile
- Founders: Vipul Ved Prakash (CEO, former Apple/Topsy), Ce Zhang (CTO), Percy Liang (Stanford Professor), and Tri Dao (Chief Scientist, creator of FlashAttention).
- Headquarters: San Francisco, California.
- Funding: Raised over $534 Million total.
- Key Investors: Salesforce Ventures, NVIDIA, General Catalyst, Coatue, Kleiner Perkins, Lux Capital.
Key Use Cases
| Use Case | Description |
|---|---|
| High-Performance Inference | Companies like Zoom and Quora use Together’s API to run open-source models at scale, achieving the speed necessary for real-time user interactions. |
| Sovereign Fine-Tuning | Healthcare and legal firms fine-tune Llama models on their proprietary documents inside a Together VPC, creating expert models without data leakage. |
| Complex Reasoning | Developers use the MoA (Mixture of Agents) API to solve difficult logic puzzles or coding tasks by pooling the “brainpower” of multiple open models simultaneously. |
Why It Matters
Together AI is the engine room of the Open Source rebellion. By making it faster and cheaper to run open models than closed ones, they are removing the economic incentive to rely on Big Tech monopolies. They prove that with the right software optimizations (like FlashAttention), “Open” doesn’t just mean “Free”—it means “Faster.”
