Senior Founding Engineer ($220K-$280K + Equity) | Frontier AI Customers, Mid-7 Figure ARR, Team of 8

Location: San Francisco, CA (5 days in-office) Visa transfers available | Relocation support considered on a case-by-case basis Company Description Venture-backed AI infrastructure startup building the data and evaluation layer behind the next generation of intelligent systems. Recently raised $4M+ from a highly respected group of Silicon Valley investors and already working with some of the most advanced AI organizations in the world. With a team of fewer than 10 people, they have reached mid-7-figure ARR and are growing faster than the team can currently support. Job Description Join one of the earliest engineering teams building critical infrastructure for frontier AI. This company sits at the intersection of agentic systems, evaluation, and large-scale data generation. Their platform helps train, evaluate, and improve advanced AI systems by creating high-quality datasets and simulation environments that capture how real work gets done. As a Senior Founding Engineer, you'll work directly with the founders to solve difficult backend, infrastructure, and AI-adjacent systems challenges. This is a highly technical role for someone who enjoys building from first principles, operating with significant ownership, and staying close to the frontier of AI tooling and agent development. Why this role is remarkable Work directly with some of the world's leading AI organizations on problems that influence how future models are trained and evaluated Join as one of the earliest engineering hires with meaningful ownership, direct founder access, and 0.7-1.0% equity Help shape both the technical architecture and engineering culture of a company already generating significant revenue with a team of fewer than 10 people Operate at the intersection of agents, evaluation systems, infrastructure, and large-scale data pipelines rather than traditional SaaS workflows What you will do Own and scale backend infrastructure, distributed systems, cloud compute, workers, and internal platforms that power the company's data generation and evaluation workflows Build and iterate on agentic systems, model harnesses, evaluation frameworks, and AI-adjacent infrastructure used in production environments Design tooling and workflows that improve data quality, operational efficiency, and system reliability at scale Work directly with founders on technical strategy, architecture decisions, and execution priorities Help raise the technical bar of a small but highly ambitious engineering team through strong judgment and engineering maturity The ideal candidate 3-7 years of experience in software engineering, infrastructure engineering, ML infrastructure, or related technical fields Experience at an early-stage startup, ideally Seed through Series A, where you operated with significant ownership and ambiguity Hands-on experience building, evaluating, or iterating on LLM agents, agentic systems, model harnesses, or AI workflows Strong backend and infrastructure foundations including cloud platforms, distributed systems, Python, and production-scale services Deep curiosity about the AI ecosystem and a habit of experimenting with new models, frameworks, and tooling as they emerge Comfortable operating autonomously with limited direction and a strong bias toward shipping Strong signals Agent evaluation, benchmarking, or measurement experience Experience preparing datasets for fine-tuning or post-training workflows Building AI products rather than solely training traditional machine learning models Demonstrated history of tackling unusually difficult technical problems Less ideal backgrounds Traditional ML focused primarily on computer vision, recommendation systems, or model training without agentic systems exposure Large-company infrastructure experience without evidence of startup execution or ownership Backend engineering experience without meaningful exposure to AI systems Next steps Apply through this LinkedIn job post. We'll review applications and reach out directly if there is a strong match. If aligned, we'll facilitate an introduction to the founding team. If this role isn't the right fit, we may suggest other high-signal startup opportunities that better match your background, always with your permission. This is a real and active search being conducted in close partnership with the hiring team. We work directly with founders on their actual hiring needs and do not post speculative opportunities. #J-18808-Ljbffr CoffeeSpace