A developer builds a LangChain RAG chain and adds MLflow tracing. Tracing confirms the retrieved context is passed correctly to the LLM, but the LLM still hallucinates product specifications not found in the retrieved chunks. What is the most likely cause and fix?

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B. The system prompt does not explicitly instruct the model to answer only from the retrieved context, so the LLM supplements retrieved content with its own parametric knowledge.. A common RAG failure mode is that the LLM is not explicitly grounded to the retrieved context. When the system prompt lacks explicit instructions like "Answer only using the provided context. If you don't know, say you don't know," the LLM supplements retrieved content with its own memorized knowledge, which may be outdated or incorrect. Adding explicit grounding instructions in the system prompt is the standard fix.

A developer builds a LangChain RAG chain and adds MLflow tracing. Tracing confirms the retrieved context is passed correctly to the LLM, but the LLM still hallucinates product specifications not found in the retrieved chunks. What is the most likely cause and fix?

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