Senior Product Engineer

Blacksmith Software Inc.; New York (NY); On-site; USD 140,000 - 180,000; Full time

Job summary

Blacksmith Software Inc. is seeking a seasoned frontend engineer to drive Codesmith, our background coding agent, and to ship fast, robust UI across our analytics platform.

You will work closely with design and engineering to deliver high-performance experiences that help engineers debug and optimize CI workloads. You’ll bring strong CS fundamentals and deep React expertise, and you’ll thrive in a fast-paced, early-stage startup environment based in New York City, with in-person collaboration

Qualifications

• Strong CS fundamentals and solid grounding in algorithms and data structures.
• Proficient in React and modern frontend development.
• 5+ years of software development experience in product teams.
• Willingness to work in person in NYC five days a week.

Responsibilities

• Build and evolve Codesmith, the background coding agent, including UI and infrastructure.
• Create tools to help engineers and AI agents debug flaky CI jobs and diagnose failures quickly.
• Collaborate with design to ship polished, high-performance frontend surfaces across analytics and observability features.
• Prototype and iterate AI-powered features from UI to backend services, owning end-to-end delivery.
• Contribute to the architecture of the agent platform and sandboxed workspaces.

Skills

React

Frontend development

CS fundamentals

UI/UX

JavaScript/TypeScript

5+ years exp

Job description

Open — Blacksmith Software Inc. has a posting for this job. Posted 24 Aug 2026.

About this job

About Blacksmith

• We 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 week, running CI for 7,000+ companies and tens of millions in ARR. We’ve grown 10x so far in 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 Partners, 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 on

• Build and evolve Codesmith, our background coding agent — designing the workflows, UI, and infrastructure that let engineers delegate coding tasks to AI and ship faster
• Create 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 intuitive
• Work closely with design to ship polished, high-performance product surfaces across our analytics and observability platform, where engineers go to understand their CI systems
• Prototype 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 UI
• Contribute to the architecture of the agent platform: how we run sandboxed workspaces, and orchestrate agent sessions

You are a good fit if you

• Have strong CS fundamentals and a deep understanding of React and modern frontend development.
• 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.

Bonus

• You’ve dabbled in your own side hustles or start-up projects.
• You’re comfortable creating new processes and iterating on them quickly.