Lead Principal Software Engineer

Siena Partnership is working with a high-growth B2B SaaS and Applied AI business building production-grade AI products for enterprise customers. The Lead Principal Software Engineer will embed with B2B software companies to identify and deliver AI and LLM opportunities, taking solutions from prototype through production while remaining hands-on across engineering and deployment.

Responsibilities:

• Embed directly into B2B software companies, working alongside CTOs, CPOs and engineering teams to identify where AI and LLMs can create meaningful product or workflow value within portfolio businesses
• Take solutions from idea and prototype through to production, building agentic workflows, LLM-powered products, RAG systems and other applied AI capabilities within existing codebases, infrastructure and engineering constraints
• Remain hands-on across architecture, coding, testing, deployment and production hardening