Poolside builds AI foundation models and a developer platform purpose-built for software engineering. Founded in 2023 by Jason Warner (former GitHub CTO) and Eiso Kant, its core IP is Reinforcement Learning from Code Execution Feedback (RLCEF) — models learn by running and testing actual code, not just predicting tokens from human feedback. Its flagship Laguna model family spans large MoE architectures for complex multi-file tasks and a compact quantized model for sub-200ms IDE completions. In July 2026, it open-sourced Laguna S 2.1, a 118B-parameter MoE that matches models many times its size on agentic coding benchmarks. The go-to-market targets enterprises with large developer workforces — banks, government agencies, and defense contractors — via on-premise or private-cloud deployment rather than generic API access. Each customer deployment is fine-tuned on that customer's proprietary codebase. Poolside also sells as a first-party offering on AWS Bedrock. Headquartered in San Francisco and Paris, the company has roughly 62 employees — a deliberately lean lab competing at frontier scale.