Staff Software Engineer: Agent Runtime & AI Systems

Helios; New York (NY); On-site; USD 140,000 - 190,000; Full time

Job summary

Helios, based in New York City, is seeking a Staff/Senior Software Engineer in Agent Engineering to advance its Proxi platform. The role is full-time and on-site in SoHo, with collaboration directly under the CTO and founding team.

You will own the agent runtime, improve long-running workflows, and ensure safe tool interactions within a regulated, high-stakes environment. You will work on retrieval, memory, provenance, and model-runtime engineering across providers, focusing on performance,

Qualifications

• Shipped production LLM/agent systems beyond prototype stage.
• Diagnose nondeterministic failures and enforce boundaries between model judgment and deterministic software.
• Decide when a workflow requires autonomy, human approval, or conventional application logic.

Responsibilities

• Own Proxi’s agent runtime and strengthen foundations for building new agent-driven products.
• Build the systems that allow agents to own long-running work from assignment through completion; keep activity visible, steerable, and connected to projects, people, evidence, deadlines, and deliverables in Action Rail.
• Build the tool and action framework agents use to interact with internal systems and external services safely.
• Connect agents to Proxi’s retrieval and knowledge systems so reasoning, memory, citations, and artifacts remain grounded in evidence.
• Improve the evaluation and release discipline for agent behavior, traces and simulations to control latency, cost, and risk.

Skills

Agent runtime engineering

Stateful orchestration

Tool and action framework

Evidence management

Security and compliance

Job description

Helios, based in New York City, is seeking a Staff/Senior Software Engineer in Agent Engineering to advance its Proxi platform. The role is full-time and on-site in SoHo, with collaboration directly under the CTO and founding team.

You will own the agent runtime, improve long-running workflows, and ensure safe tool interactions within a regulated, high-stakes environment. You will work on retrieval, memory, provenance, and model-runtime engineering across providers, focusing on performance,