Senior Product Engineer

About BlacksmithWe started by building infrastructure to run CI workloads really fast. Our first product helps companies run GitHub Actions substantially faster and cheaper by owning and operating our own global fleet of bare-metal machines rather than renting generic cloud VMs.Today, we orchestrate tens of millions of Firecracker VMs each month, running CI for 3,000+ companies and hit ~$10M in ARR in less than 2 years. We’ve already more than 5X’d revenue since the start of 2026.We operate thousands of bare-metal machines across multiple regions, regularly schedule 100k+ vCPUs concurrently, and run a petabyte-scale Ceph cluster that we manage ourselves.We’ve raised $58.5M from Seed to Series B, led by Google Ventures (GV) & Peak XV Capital, and we’re intentionally building a small, but exceptional team.Blacksmith was founded by a team with deep systems and scaling experience, including building search/ads infrastructure at Faire, and operating large distributed systems at Cockroach Labs. Our GTM is led by Jon Boyer, formerly Head of Sales at Zapier.We’re now extending the same CI infrastructure into a broader platform: running agent sandboxes at scale and building our own background coding agent on top of it.What you could work onBuild and evolve Codesmith, our background coding agent — designing the workflows, UI, and infrastructure that let engineers delegate coding tasks to AI and ship fasterCreate tools that help engineers and AI agents debug flaky CI jobs: surfacing patterns in test failures, correlating logs with infrastructure signals, and making root cause analysis fast and intuitiveWork closely with design to ship polished, high-performance product surfaces across our analytics and observability platform, where engineers go to understand their CI systemsPrototype and iterate rapidly on AI-powered features — from natural language interfaces to automated fix generation — and own the full stack from prompt design to backend service to UIContribute to the architecture of the agent platform: how we run sandboxed workspaces, and orchestrate agent sessionsYou are a good fit if youHave strong CS fundamentals and a deep understanding of React and modern frontend development.Can work closely with design to build polished, high-performance UIs — and aren’t afraid to go deep on browser performance, rendering bottlenecks, or complex component architecture.Have 5+ years of software development experience.Enjoy working in person 5 days a week in NYC.Enjoy working at a very early-stage startup and are comfortable with ambiguity.BonusYou’ve dabbled in your own side hustles or start-up projects.You’re comfortable creating new processes and iterating on them quickly.Compensation and benefitsMedical, Vision, and Dental insurance.Competitive base + equity.401K match.Unlimited PTO.Annual offsite.Early-exercise stock options 12 weeks fully paid parental leave (US)