Poolside

Startup · Paris, France

Poolside is arguably the most important "import" to the European AI ecosystem in the last decade. Founded by Jason Warner (former CTO of GitHub) and Eiso Kant, the company started in the United States but relocated its headquarters to Paris in 2024 to tap France's deep talent pool in mathematics, systems engineering, and AI research. Its mission is unusually ambitious: not just to build code autocomplete, but to create the world's most capable AI for software engineering, with a long-term goal of systems that can build and evolve software autonomously. This framing has made Poolside a defining player in the AI-for-developers category. By 2026, Poolside has established itself as a core node in the "Paris AI Triangle" alongside Mistral and H. After a massive $500M Series B in late 2024 led by Bain Capital Ventures, the company launched its flagship foundation model trained on a distinct corpus of code, software architecture, and repository-level structure. The emphasis on engineering artifacts rather than general internet text allows Poolside's models to reason about large codebases, infer intent from architectural patterns, and propose higher-level refactors instead of one-off snippets. This technical posture differentiates Poolside from generalist models and makes it uniquely useful for enterprises grappling with decades of technical debt. The company's 2026 platform looks less like a plugin and more like a "shadow engineering team." Poolside can analyze legacy banking systems, plan migrations across stacks, and coordinate changes across modules while preserving compliance and auditability. That capability has made it a darling of large financial institutions such as HSBC and Citi, and it explains why strategic investors are embedded alongside venture capital. Poolside is also scaling Project Horizon, a 2-gigawatt AI data center campus in Texas in partnership with CoreWeave, while keeping its research and model development anchored in Paris. This split setup reflects a broader pattern: US-scale compute, European R&D depth. Poolside's ecosystem ties are deep. It is a central node at Station F and an active participant in the Paris AI Hub, and its relocation is often cited by the French government as a proof point for attracting foreign tech leadership. The investor roster underscores its strategic importance: Bain Capital Ventures led the growth round, DST Global joined as a late-stage backer, Xavier Niel provided early strategic support to facilitate the Paris move, and Nvidia is a hardware partner. In 2026, Poolside stands out as Europe's most credible attempt to build an AI-native software engineering stack at frontier scale.

https://poolside.ai