Frontend Engineer, Core Platform

About Lumbra Lumbra builds the vendor-neutral operating system for agentic AI in high-consequence environments. In our first ten months we won four fully competed prime contracts across the U.S. Government, every one of them deploying into classified spaces. We are live on JWICS. We were selected from a field of 200+ companies for a defense innovation challenge and won it. We beat two established defense primes on the same program and earned the follow-on, now in execution. About the Role Nebula, our agentic harness, turns days of manual synthesis into minutes of analysis. Whether analysts trust it depends heavily on the interface: how an agent's work streams in, how its sources and reasoning are shown, and how quickly someone can move through dense, connected data under pressure. We want a frontend engineer to own that experience. You build the React and TypeScript application analysts use every day, make it fast and legible, and make sure it works the same in commercial cloud and on disconnected, classified networks. This role is on site in Arlington, Virginia. It is not eligible for remote or hybrid work. How the Role Is Structured - ~70% building. Product features in React and TypeScript, from conversation interfaces to workflow and graph views. - ~20% quality and performance. Testing, render performance, accessibility, and the shared components the rest of the team builds on. - ~10% users and product. Working with Forward Deployed Engineers and analysts to turn feedback from the field into interface changes. What You'll Own - Conversation and streaming interfaces for agent output, including tool calls, citations, confidence, and long-running work that has to recover cleanly from timeouts and reconnects. - Workflow and knowledge-graph visualization that keeps dense analytical data legible. - Front-end architecture: state management, data fetching, API contracts with the backend, and patterns that survive constant change. - Shared components and the design system in code, so new features look and behave consistently. - Performance and accessibility, measured rather than assumed. You profile before guessing and treat slowness as a defect. - Front-end testing: component, integration, and end-to-end tests that cover the spec rather than the implementation. - Builds that work disconnected, with no reliance on external CDNs, fonts, or services, so the same app runs inside air-gapped deployments. You'll Work Alongside CIA officers, MIT engineers, Special Operations combat veterans, and applied AI engineers from frontier labs including Anthropic and Google. You will make decisions that immediately affect national security. You will own part of a company early and when it matters. What This Role Is Not - A pixel-pushing role. You shape the experience, not just implement mockups. - A role where performance is someone else's problem. - A backend role. You'll read and shape API contracts, but your depth is the front end. Required Qualifications - Real depth shipping production front-end software in React and TypeScript. We care about what you have owned and the depth of your experience, not a year count; engineers with 2+ years who have owned meaningful front-end systems are welcome. - Experience building interfaces for real-time or streaming data, such as WebSockets or server-sent events, including the state model behind them. - Real depth in component design, state management, and render performance, with examples of problems you profiled and fixed. - Clean, well-tested code, including component and end-to-end tests. - Enough backend fluency to read and shape API contracts; Python is a plus. - Comfort taking a loose ask and turning it into a working interface without a finished design. - A humble, hands-on approach. - Willingness to work on site in Arlington, Virginia. Preferred Qualifications - Experience building LLM or agent interfaces, including streaming output, tool-call visualization, and citation surfacing. - Experience with data visualization or graph exploration libraries. - Experience building or maintaining a design system. - Experience with accessibility (WCAG) in complex applications. - Experience building analytical, intelligence, financial, or developer-facing tools. - Experience shipping front ends into restricted or offline environments. - An active U.S. security clearance, or eligibility to obtain one. Compensation The base salary range for this role is $120,000 to $300,000, spanning our Engineer II and Senior Engineer levels. Where an offer lands depends on scope, autonomy, and technical capability, which we assess through the interview process rather than by years or title. Our ranges are a real guide, and we are flexible for the right person: if your experience clearly exceeds this role's scope, we will consider you at a higher level, with that level's range. Base salary is one part of total compensation, alongside equity and the benefits below. What We Offer - Health, dental, and vision insurance. 99% of your premiums covered, and 100% of your dependents' premiums. - Optional HSA plan. Lower premium, HSA eligible, fully portable, self-directed or managed. - Health Reimbursement Account for qualified healthcare expenses. - Life insurance of $150,000 plus AD&D, 100% company paid. - 401(k) with a 100% match on the first 6%, immediately vested. No cliff, no waiting period. Yours from day one. - Wellhub Gold. Everything from Gold's Gym to Lifetime, fully covered, plus [solidcore], F45, and hundreds of other studios. - Unlimited PTO. Real time off, not accrual-based. Take what you need, no counting required. - Every federal holiday, plus additional paid days off over the winter break. - Supportive leave of absence program, including time off for military service, medical events, and parental leave. - Breakfast, lunch, and endless snacks every day you are in the office. - Pre-tax commuter benefits. - Company phone plan. A new iPhone, fully company paid.