Principal Full Stack Engineer

Principal Full Stack Engineer We are Lennar Lennar is one of the nation's leading homebuilders, dedicated to making an impact and creating an extraordinary experience for their Homeowners, Communities, and Associates by building quality homes and providing exceptional customer service, giving back to the communities in which we work and live in, and fostering a culture of opportunity and growth for our Associates throughout their career. Lennar has been recognized as a Fortune 500® company and consistently ranked among the top homebuilders in the United States. About the Role Lead the architecture and delivery of production-grade AI-powered systems across the full stack. Operate at the intersection of applied AI research and software craftsmanship - designing agentic workflows, integrating large language models, and establishing engineering practices at scale. Serve as the technical standard-bearer for how the organization builds, evaluates, and operates AI features. Partner with Engineering and Data to translate ambiguous business problems into concrete technical roadmaps. Drive AI engineering strategy across the stack, authoring RFCs and leading design reviews that raise the bar for the entire engineering org. What You'll Do Design and own end-to-end AI features: from prompt engineering and model selection through to scalable APIs and responsive front-end surfaces. Architect multi-agent and agentic workflow systems using frameworks such as LangGraph, CrewAI, AutoGen, or custom orchestration layers. Build retrieval-augmented generation (RAG) pipelines with production-grade chunking, embedding, indexing, and reranking strategies. Integrate LLM providers (OpenAI, Anthropic, Gemini, local models via Ollama / vLLM) with robust fallback, rate-limiting, and cost controls. Deliver polished, accessible front-end experiences in React that expose AI capabilities with low latency and graceful degradation. Build and maintain high-throughput back-end services in Node.js, or Go serving as the inference and orchestration layer. Define and implement LLM evaluation frameworks evals, red-teaming, regression suites to continuously measure model quality in production. Instrument AI pipelines with tracing, latency histograms, and cost dashboards using tools such as LangSmith, Helicone, or Grafana.. Embed responsible-AI practices: hallucination mitigation, PII redaction, output guardrails, and bias monitoring into every feature. Mentor senior engineers, conduct rigorous code and architecture reviews, and contribute to hiring by defining role expectations and screening candidates. What We're Looking For 8+ years of professional software engineering with at least 2 years building production AI / ML systems. Expert-level proficiency in Go and TypeScript / JavaScript; comfortable owning the full stack from model to UI. Hands-on experience designing and shipping LLM-powered features including prompt engineering, fine-tuning, and RLHF concepts. Deep understanding of transformer architectures, token economics, context window management, and inference optimization. Proven track record with RAG architectures, embedding models, and semantic search at scale. Strong grasp of distributed systems, API design, and cloud-native infrastructure (AWS).. Experience with MCP (Model Context Protocol), tool-use patterns, and multi-agent orchestration in production. Demonstrated ability to lead without formal authority, influencing direction through technical credibility and clear communication. Contributions to open-source AI projects or published technical writing on AI engineering topics preferred. Experience in regulated or enterprise environments where auditability, security, and compliance are first-class concerns is a plus. Life at Lennar At Lennar, we are committed to fostering a supportive and enriching environment for our Associates, offering a comprehensive array of benefits designed to enhance their well-being and professional growth. Our Associates have access to robust health insurance plans, including Medical, Dental, and Vision coverage, ensuring their health needs are well taken care of. Our 401(k) Retirement Plan, complete with a $1 for $1 Company Match up to 5%, helps secure their financial future, while Paid Parental Leave and an Associate Assistance Plan provide essential support during life's critical moments. To further support our Associates, we provide an Education Assistance Program and up to $30,000 in Adoption Assistance, underscoring our commitment to their diverse needs and aspirations. From the moment of hire, they can enjoy up to three weeks of vacation annually, alongside generous Holiday, Sick Leave, and Personal Day policies. Additionally, we offer a New Hire Referral Bonus Program, significant Home Purchase Discounts, and unique opportunities such as the Everyone’s Included Day. At Lennar, we believe in investing in our Associates, empowering them to thrive both personally and professionally. Lennar Associates will have access to these benefits as outlined by Lennar’s policies and applicable plan terms. Visit Lennartotalrewards.com to view our suite of benefits. Join the fun and follow us on social media to see what's happening at our company, and don't forget to connect with us on Lennar: Overview | LinkedIn for the latest job opportunities. Lennar is an equal opportunity employer and complies with all applicable federal, state, and local fair employment practices laws.