Build and operate the backend for Bilt’s AI-powered Concierge across chat, SMS, email, and iMessage. Responsibilities include agent tools and workflows, multi-agent orchestration, model routing, distributed systems, messaging, authentication, performance optimization, evaluation harnesses, and proactive engagement features. The role requires production backend experience, LLM familiarity, cloud service operation, strong distributed-systems fundamentals, product judgment, AI coding-agent usage, and clear technical writing.