Staff/Senior Software Engineer, Agent Engineering (Helios)

Staff/Senior Software Engineer, Agent Engineering New York City | Full-time | On-site in SoHo, five days per week Reports to the CTO and works directly with the founding team ABOUT HELIOS Helios is building a new kind of company to solve America’s hardest problems, starting with the government interaction layer. Government shapes every consequential market, but the infrastructure connecting public institutions and private organizations remains fragmented, manual, and difficult to navigate. Helios is rebuilding that layer. Our core platform, Proxi, gives organizations the intelligence they need to understand what government is doing, why it matters, and what to do next. From that foundation, we design and deploy secure, mission-specific systems for government agencies, enterprises, and institutions operating in complex and highly regulated environments. We bring together frontier AI, deep public-sector expertise, and forward-deployed execution. Our team includes leaders and builders from the White House, U.S. Department of State, Datadog, and Microsoft. We are backed by leading institutional investors and trusted by organizations working on high-stakes problems across government and industry. Advance the agent runtime that powers Proxi’s research, analysis, and action capabilities. Our agents must decompose open-ended objectives, retrieve trustworthy evidence, use tools safely, coordinate long-running work, and produce high fidelity outputs that remain traceable to their sources. At Helios you will own the systems that make agent behavior reliable in production, including execution state, tool use, context, memory, model routing, recovery, evaluation, and security - improving Proxi’s ability to perform meaningful work over hours without losing context, exceeding their authority, silently failing, or producing unsupported conclusions. You will also advance the reasoning and memory layer built on top of the Helios Rapid Ontology System (H.R.O.S.), enabling agents to accumulate knowledge, recognize change, resolve contradictions and carry direct source context across workflows. We are looking for a senior engineer who has shipped production LLM or agent systems beyond the prototype stage. You should be comfortable diagnosing nondeterministic failures, enforcing boundaries between model judgment and deterministic software and deciding when a workflow requires autonomy, human approval, or conventional application logic.