Is Conformal Factuality for RAG Robust? Novel Metrics Show Distribution Shifts Break Statistical Guarantees

arXiv 2603.16817·medium signal

RAG + conformal factuality filtering was proposed as a way to provide distribution-free statistical reliability on LLM outputs, but this 56-page study finds the guarantees are fragile under distribution shift. The paper introduces novel robustness metrics for conformal factuality and reveals systematic failure modes that practitioners deploying RAG with reliability guarantees need to account for. Key finding: the statistical coverage guarantees degrade in ways that are hard to detect without explicit robustness testing.