RadixArk, an AI infrastructure company founded by the creators of the open-source inference engine SGLang, has launched with $100 million in seed funding at a $400 million post-money valuation. The round was led by Accel and co-led by Spark Capital, with participation from NVentures, Salience Capital, A&E Investments, HOF Capital, Walden Catalyst Ventures, AMD, LDV Partners, WTT Investment, and MediaTek. A broad group of angel investors joined the round, including the CEOs of Intel and Broadcom, the co-founder of xAI, and the co-founder of OpenAI.
The company was founded by Ying Sheng and Banghua Zhu, AI infrastructure veterans from xAI and NVIDIA. In 2023, Sheng and collaborators created SGLang, which has since become a de facto open-source standard for serving large language models at scale. The engine now runs across hundreds of thousands of GPUs worldwide and generates trillions of tokens daily for companies including Google, Microsoft, NVIDIA, Oracle, AMD, and xAI. RadixArk will steward SGLang while building a commercial end-to-end platform that supports the full model lifecycle — training proprietary models, fine-tuning open models, running reinforcement learning, and deploying inference at scale.
The company’s mission centers on the argument that frontier AI infrastructure has become increasingly inaccessible, confined to a handful of large technology companies. RadixArk aims to reverse that concentration by providing managed infrastructure and tooling that any developer, startup, enterprise, or research lab can use. The platform is built on two open-source foundations: SGLang for inference and Miles, the company’s own framework for large-scale reinforcement learning.
Alongside its commercial platform, RadixArk carries forward the open-source ethos of SGLang’s origins at LMSys, a nonprofit research organization founded by researchers from Stanford, Carnegie Mellon, and UC Berkeley. SGLang supports virtually every major open model family and hardware provider at launch.
KEY QUOTES:
“Our mission is simple yet ambitious: make frontier-level AI infrastructure open and accessible to everyone. We believe the next generation of AI won’t be defined by who owns the biggest private infrastructure, but by who builds the most meaningful applications on top of shared, world-class systems. We aim to make these systems orders of magnitude cheaper and more accessible, so everyone can build on them.”
Ying Sheng, Co-Founder and CEO, RadixArk
“RadixArk is building the open foundation for the next era of AI — where companies don’t just consume models, they train and manage them as a core part of product development. By democratizing training and inference infrastructure, RadixArk enables any engineer to experiment and innovate at the frontier, fully owning how AI powers their products.”
Ivan Zhou, Partner, Accel
“SGLang is the absolute best inference framework for large language models. It was a crucial part of the infrastructure at xAI, because it enabled folks to run large models faster and more efficiently than many alternatives. I’m excited to see Ying and Banghua expand that vision with RadixArk.”
Igor Babuschkin, Co-Founder, xAI
