Agentic AI and LLM Applications Software Development Engineer, Senior

The Opportunity

The GRACE team at ARPA-H is building the next generation of agentic AI to transform how the agency accelerates research, makes decisions, and ships products at scale. GRACE is ARPA-H's production AI assistant, and we are evolving it into an ecosystem of autonomous, multi-agent systems.

We are a small, startup-minded team that ships fast and owns what we build end-to-end. We are looking for a senior SDE who lives at the application layer: designing and building the agentic workflows, LLM integrations, tool-calling systems, and AI-powered features that GRACE users interact with every day. Your focus is on what runs on top of the platform: the agents, the orchestration, the prompts, the pipelines, and the product.

The best person for this role starts with the user. They ask why before they ask how. They communicate clearly, give and receive feedback well, and make the people around them better. They are a self-starter with a high bar, a high sense of urgency, and genuine empathy for the people whose work they are making better.

What You'll Do:

• Design and build GRACE's core agentic workflows: multi-step reasoning, planning, memory, and tool-use across single and multi-agent systems
• Implement and evolve A2A communication patterns at the application layer, enabling GRACE agents to collaborate and hand off tasks
• Build and maintain the tool-calling layer: tool definitions, input/output schemas, error handling, retry logic, and result formatting
• Own the MCP client-side integration: how GRACE agents discover, invoke, and compose tools exposed via MCP servers
• Design multi-agent workflows that are reliable, observable, and debuggable in production, not just in demos
• Own LLM orchestration at the application layer: prompt construction, context management, model selection logic, and response parsing
• Build and maintain RAG features: query formulation, result ranking, citation grounding, and hallucination mit