Why RAG Systems Fail: The Routing Problem Behind Wrong Answers

Retrieval-Augmented Generation (RAG) systems can return incorrect answers even when they retrieve seemingly relevant documents, because the source of that document may be outdated, deprecated, or low-authority. The core issue is routing — determining which knowledge source should be trusted for a given query, user, and context — not just which chunks are semantically similar. In multi-source RAG deployments, treating all indexed documents as equally valid causes production failures, such as surfacing abandoned design docs over current official references. Experts recommend routing queries based on intent, user permissions, source authority, and document freshness before retrieval even begins. Conflicts between sources should be resolved using provenance and precedence rules, and routing quality should be evaluated independently from retrieval and generation performance.