Poolside

poolside is an AI research and product lab building large language models specialized for software development, founded in early 2023 by CEO Jason Warner (former GitHub CTO and Heroku/Canonical engineering leader) and CTO Eiso Kant (previously founder of source{d} and Athenian). Rather than building a general-purpose model, poolside trains its models using what it calls Reinforcement Learning from Code Execution Feedback (RLCEF), pairing its own foundation models with an internal 'Model Factory' system for training and evaluating coding-focused AI. The company is headquartered in San Francisco with a distributed team across the US, UK and France, and sells private, enterprise-deployed coding assistants to large customers in defense, financial services, industrial manufacturing, software and the public sector, including a relationship with the U.S. Department of Defense. In July 2026, poolside released Laguna S 2.1, a 118-billion-parameter open-weight mixture-of-experts coding model, under an OpenMDW-1.1 license, claiming benchmark results that match or beat open models several times its size on agentic coding tasks. In August 2026, Nvidia struck a non-exclusive $6 billion licensing deal for poolside's Model Factory technology and invested $1 billion in the company at a $12 billion pre-money valuation, with more than 100 poolside engineers moving to Nvidia to work on its Nemotron open-weight model project while poolside's founders remained with the company.