Senior Member of Technical Staff, Harness Engineering

About the role

The model is only one part of a worker. The loop, the tools, the memory, the execution environment, the guardrails, the fallback path, the observability - that's what decides whether an agent can actually do useful work inside a real company. That's the harness, and at Harper every agent (product and coding) rides on a shared one. If the harness is brittle, every pod ships brittle agents; if it's good, pod engineers stop rebuilding the same scaffolding and start shipping agents in days instead of weeks. That makes the harness the company-specific leverage behind the whole bet - the model is replaceable, the substrate beneath it is the moat. You'll build inside the harness layer - the meta-harness wrapping our frontier coding agents, OpenClaw, Hermes, and our internal agents - working alongside the engineer setting harness direction, shipping the primitives every agent team depends on.

Responsibilities

• Build agent-loop primitives. Prompt construction, tool routing, retry/timeout/budget logic, multi-step orchestration.
• Ship execution-environment infra. Sandbox lifecycle, isolation, blast-radius limits, filesystem and network policy for agents.
• Own the tool layer for your domains. Schema, auth, rate-limit, observability per tool - tools other engineers build on.
• Wire model-provider routing. Provider fallback chains, eval-driven model selection, cost/latency tradeoffs.
• Ship harness SDK improvements - whatever makes pod engineers faster.
• Eat your own dog food. You write code with our harness daily and feel every rough edge before anyone else reports it.

Requirements

• 3-6 years building software, with production agentic systems behind you (real users, real traffic - not demos) and experience with at least one major agent framework.
• You think in tool design, not just prompt design, and can describe a tool-design or sandbox decision you'd still defend in three years.
• Production agent/LLM systems experience: agent loops, tool integration, prompt engineering at scale.
• You write code with AI daily and manage 3+ parallel sessions.
• Strong written communication (API contracts, integration guides, internal docs).
• Bonus: sandbox/isolation infrastructure; open-source agent-framework contributions; foundation-model partner or early-access experience.
• The reality
• Logistics
• Compensation (OTE): $187,000-$264,000 cash (base + target performance bonus), plus competitive equity.
• Location: San Francisco, in-office. Based here or willing to relocate.
• Benefits: Uber commuter benefits; breakfast, lunch, and dinner provided; snacks and coffee stocked; free gym membership; health, dental, and vision.
• Process: Founder call (15 min) → Tech Lead deep-dive (60 min, harness) → Super Day on-site → founder + Tech Lead offer. No committee. Best offer, first.
• To apply: If you've shipped an agent loop or a tool layer that real engineers depend on - send your resume, the code, and tell us about a harness decision you'd defend.

Benefits

Additional Information

Senior Member of Technical Staff, Harness Engineering Harper is an AI-native commercial insurance company in San Francisco. We're not bolting AI onto insurance - we're rebuilding the entire business as software, on a simple bet: turning expert human judgment into compute is one of the largest transitions left to make, and a trillion-dollar industry still run 90% by hand is the place to prove it. We've grown ~100x in the last year and we move at that speed - on-site, in person, long days, very high standards. Almost no one joins Harper for insurance ; they join to build the company that replaces how it works.

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