Full-Stack Engineer for AI Agent Platform

Ersilia; San Francisco (CA); On-site; USD 200,000 - 400,000; Full time

Job summary

Ersilia, based in San Francisco, is seeking a Full-Stack Engineer to own the product experiences and agent infrastructure that make the agent improvement loop legible and actionable for engineering teams.

You will talk to customers, define what to build, implement it, and iterate until the product delivers value across data layer to UI, including agent swarm interfaces, verification platforms, and the SDK.

Qualifications

• Experience building and scaling end-to-end production systems, from data layer to UI.
• Hands-on experience building with LLMs or agents, or demonstrable drive to get there fast.
• Comfort working directly with customers to understand needs and solve real-world problems.

Responsibilities

• Shape how our Agent runs large-scale parallel investigations across thousands of production traces, merging failure modes and drift signals into a single actionable answer.
• Build the platform for verifying agent changes: hosted simulated environments for stateful agent evals and trajectory replay.
• Design how engineers understand long traces, tool calls, decisions, and failures—making complex reasoning trajectories legible.
• Build the swarm UX so engineers can monitor parallel investigations and steer investigations in the right direction.
• Own the improvement loop: workflows turning production trajectories into datasets, judges, and regression checks.
• Own platform infrastructure: workspaces, roles, permissions, billing, usage, and limits for teams running many agents.

Skills

End-to-end systems

LLMs/agents

Customer-facing

Problem-solving

Communication

In-person in SF

Job description

Ersilia, based in San Francisco, is seeking a Full-Stack Engineer to own the product experiences and agent infrastructure that make the agent improvement loop legible and actionable for engineering teams.

You will talk to customers, define what to build, implement it, and iterate until the product delivers value across data layer to UI, including agent swarm interfaces, verification platforms, and the SDK.