Founding Engineer

About Runtime

We manage sandboxed coding agents that adopt companies' best practices. We're building the infrastructure layer that makes AI coding agents safe, reliable, and aligned with how teams actually work. We're already working with a hyper-growth unicorn customer and Series B - C YC scaleups and we're just getting started.

Why We Started Runtime

After Mentum (YC S21) was acquired, Gus (CEO) personally shipped 4 full-stack products in 3 months using coding agents. When I tried to roll the same workflow out to the rest of the team, it fell apart: Most PRs were unmergeable slop, every repo required an engineer doing one-off local setup, skills and context lived in one person's head, and there was no safe way for a PM to touch a real codebase without risking a bad deploy or a secrets leak.

Carlos (CTO) comes from building agentic reconciliation systems at Modern Treasury and had a similar experience when enabling his support team use Devin.

About the Role

We're looking for a founding engineer to join us in San Francisco. You'll be one of the first hires with an outsized impact on what we build, how we build it, and the culture we create.

What You'll Do

• First month: get hands-on with our platform, ship production code, and start owning large parts of our infrastructure
• First 6 months: improve reliability of coding agent harnesses, bring on new sandbox providers, lead the architecture for our multi-cloud micro-VM sandbox infrastructure, support 50+ integrations, contribute to our core OSS project
• Work across the full stack, from sandbox infrastructure to developer-facing product
• Shape technical direction alongside the founding team

What We're Looking For

• Experience building and scaling distributed systems or complex cloud infrastructure. Containerized infra (Docker, K8s) and developer tooling experience are a strong signal
• Side projects or professional work involving LLM agents
• Daily use of coding agents for software development
• Comfort with ambiguity and moving fast in a small team
• Genuine interest in coding agents, the future of software development, and sandbox environments
• Willingness to learn and iterate quickly. This matters more than any specific tech stack