Senior/Staff Founding Full-Stack Engineer - Agent Systems
Ansius (for a Confidential Client)
San Francisco, CA
Updated on September 9, 2026
- On-site
- Full-time
- Senior
- AI Infrastructure
- $200,000 - $300,000 per year
Job Description
Our client is seeking a highly skilled Founding Full-Stack Engineer to join their early-stage team in San Francisco. This role is designed for an engineer who thrives on building complex systems from the ground up and desires a significant impact on the future of AI infrastructure. Our client is building AI coworkers specifically for IT teams, with a rigorous focus on security, identity, authorization, and reliable agent execution. While this position is backend- and systems-heavy, our client expects the successful candidate to own the product end-to-end, spanning infrastructure, APIs, and user-facing experiences. Our client provides an environment where the engineer will develop workflow systems for long-running human and AI agent tasks, design identity and authorization systems, and build secure credential infrastructure. Our client offers the opportunity to work on sandboxed environments and production-grade APIs that power the next generation of AI systems.
Requirements
Critical Requirements
- 4+ years of professional software engineering experience
- Proven experience designing and operating complex production systems
- Strong backend and systems architecture proficiency
- Ability to work in-person in San Francisco, Monday through Friday
- High level of ownership and ability to navigate ambiguity
Important Requirements
- Experience across frontend, infrastructure, data, and product layers
- Background in security, IAM, authorization, or workflow orchestration
- Experience with multi-tenant SaaS or AI infrastructure
- Strong understanding of failure modes, threat models, and system reliability
- Ability to move quickly without compromising security or correctness
Nice to Have Requirements
- Experience with permission/identity systems
- Experience with secrets or privileged-access platforms
- Experience with workflow engines and reconciliation systems
- Experience with agent infrastructure and evaluation systems
- Experience with sandboxes or virtualized execution
- Experience with enterprise integrations
- Previous experience in early-stage startups with ownership of architecture and production
About
Our client is a fast-growing AI infrastructure startup currently in the pre-seed stage. Our client is dedicated to building foundational technology for AI agents, with a specific focus on security and reliability. Our client provides a collaborative, high-impact environment for engineers who are passionate about building complex systems from day one. Our client offers competitive compensation, health insurance, unlimited PTO, and office meals, and our client provides visa sponsorship for qualified candidates including H-1B, O-1, and OPT.
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