AI Software Engineer — Frontier Lab

Substantial is embedding engineers with a well-funded frontier AI lab building generative models. You'd work directly in the lab's codebase alongside their team, in a heavily AI-native environment where most code is AI-written and human-reviewed. We're hiring at the senior, lead, and principal level only. 8+ years of professional software engineering experience is required.

Responsibilities

You'd work across the stack, a TypeScript and React frontend with a backend written in Go and Python, contributing to the lab's codebase through their standard PR and review flow, where steering and reviewing AI-generated code matters as much as writing it. Example areas of work:

• Connectors that expose customer tools to the lab's agents, for example Google Drive and Slack, by designing and shipping high-traffic REST APIs and integration backends.
• Extending the core product with enterprise functionality such as admin, billing, and permissions.

You may be a good fit if you

• Have 6+ years of professional software engineering experience.
• Have real backend depth and full-stack range, for example: schema design, distributed systems, billing and transaction systems.
• Have a solid grounding in security and authentication for APIs, OAuth flows, and integrations.
• Bring a high bar for systems design quality, with thoughtful data models, attention to failure modes, and a focus on availability, performance, correctness, and reliability at scale.
• Are fluent with agentic coding tools like Claude Code and are comfortable with AI-assisted development.
• Have strong judgment and product sense, and can tell what will and won't work and apply patterns across systems.
• Take ownership end-to-end, driving features from design through ship with high agency and minimal oversight.
• Have a track record of delivering complex software projects.

Strong candidates may also have

• Experience with large-scale, high-throughput systems.
• Agent-building experience.
• Built connectors or third-party integrations.
• Enterprise admin, permissions, or access-control work.
• Data engineering experience.
• Depth in TypeScript, Go, or Python.