Some of the team responsible for maintaining SGLang, a popular open-source tool used by companies like xAI and Cursor to speed up the training of artificial intelligence models, has moved to the recently launched commercial startup. This company, called RadixArkannounced last August.
RadixArk, which was created as SGLang in 2023 inside the UC Berkeley lab of Databricks co-founder Ion Stoica, was recently valued at about $400 million in a round led by Accel, according to two people familiar with the matter. TechCrunch could not confirm the size of the funding.
The startup previously raised angel capital from investors including Intel CEO Lip-Bu Tan, the people said.
Ying Sheng, a key SGLang contributor and former engineer at xAI, has left Elon Musk’s AI startup to become the co-founder and CEO of RadixArk, according to a LinkedIn announcement did last month. Sheng was previously a researcher at Databricks.
RadixArk’s Ying Sheng, Accel and Lip-Bu Tan did not respond to a request for comment.
Both SGLang and RadixArk focus on optimizing inference processing — essentially allowing models to run faster and more efficiently on the same hardware. Along with model training, inference accounts for a large portion of the server costs associated with AI services. As a result, tools that optimize the process can generate huge savings almost immediately.
vLLM, a more mature inference optimization project, has also been converted from an open source project to a startup. The startup has been in talks to raise more than $160 million in funding at a valuation of around $1 billion, Forbes reported last month.
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Three people familiar with the deal tell TechCrunch that Andreessen Horowitz is leading the vLLM investment, though the final numbers for that investment remain to be seen. Andreessen Horowitz declined to comment. vLLM co-founder Simon Mo called the information about that round “truly inaccurate” in a statement to TechCrunch, though he declined to specify which details were incorrect.
Like SGLang, vLLM was incubated in Ion Stoica’s lab at UC Berkeley. Stoica, a professor at UC Berkeley, is the famous co-founder of Databricks as well as a number of other startups.
Several large tech companies are already running their inference workloads using vLLM, and SGLang has also gained significant popularity over the past six months, Brittany Walker, general partner at CRV, told TechCrunch. Her company did not endorse either company.
RadixArk continues to develop SGLang as an open source AI modeling engine. The startup is also building Miles, a specialized framework designed for reinforcement learning that allows businesses to train AI models to get smarter over time.
While most of its tools remain free, RadixArk has started charging fees for hosting services, a person familiar with the company told TechCrunch.
Startups that provide inference infrastructure for developers have seen an increase in funding in recent months, highlighting the continued importance of the inference layer for AI. Baseten recently secured $300 million in one $5 billion valuationthe Wall Street Journal reported Tuesday. This follows a similar move by rival Fireworks AI, which raised 250 million dollars at a $4 billion valuation last October.
