As a Principal Engineer in HRSD, you set the technical direction for model-driven capability across the HR domain, the agentic and conversational experiences that interpret employee, manager, and HR agent intent, reason over profile, case, catalog, policy, and knowledge context, and act on the user''s behalf. Two things shape the job: much of the load-bearing logic lives in natural language - instructions, prompts, context, tool descriptions, guardrails - and must be engineered with the same discipline as code; and because behavior is probabilistic, correctness is established through evaluation at scale, not fixed assertions.