Where do vector stores and RAG corpora sit relative to agent execution layers?

Vector stores and RAG corpora sit outside the core durable agent execution layer. These external systems store unstructured data for retrieval during agent runs, but do not track execution progress or need inclusion in replayable checkpoints. Agents call these stores during workflow steps to fetch relevant context as needed. Caveat: Track retrieval calls in workflow state if audit or replay requires visibility into fetched data.