Q. Someone asks you to explain a RAG answer. What is the realistic form of FM explainability?
A. Traceability: citations back to the source passages that grounded the answer (Bedrock Knowledge Bases RetrieveAndGenerate returns them), plus documented behaviour. It is not SHAP-style per-feature attribution.
Why? Do not promise feature attribution on an LLM; explainability here is grounding and documentation.