Senior Software Engineer - AI Training Environments

What we do Idler builds reinforcement learning environments that teach AI models to code like 0.01% engineers. Our training environments are based on real-world coding scenarios that frontier models will actually encounter. We've closed a multimillion-dollar contract with a leading foundation lab (the largest they've issued to date). Demand is outpacing our capacity to deliver, so we're scaling the team fast. What you'll do Build features and tooling for our agentic systems that create and QA coding environments. You'll work alongside senior engineers and the founding team, learning how to design systems that are both technically sound and philosophically robust. A big part of our work is thinking critically about what makes a coding environment "good" and "fair". Concretely, you'll: Build UI components and backend services for environment generation and validation Implement automated testing and QA workflows Work with real codebases to understand what makes effective training data Ship features quickly and iterate based on feedback from AI researchers at leading labs You'll work with The founding team, a founding engineer, and a small group of engineers (we're hiring quickly). You'll learn directly from people building at the cutting edge of AI training. Tech stack Typescript, React, NodeJS, Postgres, Redis, Vercel, Cursor Benefits Healthcare coverage, 401(k), and 15 days PTO Meals, coffee, and snacks (that you will actually enjoy) covered during working days Latest MacBook Pro and equipment Relocation assistance available Team offsites and events (we love hanging out) This is an in-person role in San Francisco. We're a tight-knit founding team and we play to win. Join us if you like to win too.