Zillow developed a comprehensive Fair Housing compliance system for LLMs in real estate applications, combining three distinct strategies to prevent discriminatory responses: prompt engineering, stop lists, and a custom classifier model. The system addresses critical Fair Housing Act requirements by detecting and preventing responses that could enable steering or discrimination based on protected characteristics. Using a BERT-based classifier trained on carefully curated and augmented datasets, combined with explicit stop lists and prompt engineering, Zillow created a dual-layer protection system that validates both user inputs and model outputs. The approach achieved high recall in detecting non-compliant content while maintaining reasonable precision, demonstrating how domain-specific guardrails can be successfully implemented for LLMs in regulated industries.
