Founding Engineer

This is one of the first engineering roles at Lightsage. You'll join the founding team in San Francisco. You'll own systems end to end across frontend, backend, infrastructure and data, and work directly with customers to turn their problems into shipped features. Early projects include: • Improving recommendation quality, and measuring whether a recommended change actually helps a customer • Designing the experiments and benchmarks that tell us which changes actually make agents recommend and use a product • Building agents that write, publish and re-test documentation changes for customers • Adding support for new coding agents and models as they're released • Scaling eval and data pipelines for enterprise customers New models ship every few weeks, so the work changes constantly. The team builds with AI coding tools and our own agent orchestrator, and reviews all code before it ships. Requirements • Track record of taking a loosely defined customer or product problem to a shipped solution with little direction • Strong backend experience, including building reliable systems that handle production load • Hands-on experience shipping quickly with AI coding tools such as Claude Code or Codex • Clear thinking about technical trade-offs, and clear written communication • Experience doing research or running rigorous experiments, such as LLM evals, benchmarks or A/B tests, and drawing sound conclusions from noisy results is a plus • Experience with Next.js, FastAPI, Supabase or Microsoft Azure is a plus • Prior founder or early-stage startup experience is a plus This is a full-time, on-site role in San Francisco. It's a demanding schedule that regularly includes weekends, with significant ownership over the company's technical direction.