open-weight-models
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Understudy Labs
Understudy Labs is a San Francisco AI infrastructure startup (Y Combinator S26) that helps data-rich teams replace expensive frontier LLMs with smaller, specialized models they own. Its open-source toolkit captures production traces from existing agent workflows, benchmarks cheaper open-weight models against them, and only ships a replacement once a held-out evaluation beats the incumbent - promising comparable quality at a fraction of the cost and latency.
Featherless AI
Featherless AI is a serverless inference platform that gives developers and enterprises a single API key to run more than 40,000 open-weight AI models across language, vision, audio and multimodal tasks - without provisioning or managing any GPUs. Founded in 2023 by the team behind the RWKV open-source model architecture, the company sells flat-rate subscriptions with unlimited tokens and positions itself as a neutral infrastructure layer for open-source AI, independent of the major cloud hyperscalers. It raised a $20M Series A in April 2026 co-led by AMD Ventures and Airbus Ventures, bringing total funding to about $25M.
FriendliAI
FriendliAI is a San Francisco-based AI inference cloud built by the researchers who invented continuous batching - the technique now standard across the industry. Its platform serves open-weight and custom generative AI models in production with high throughput, lower GPU costs, and 99.99% reliability, used by customers including LG and Twelve Labs.