diff --git a/cookbook/langgraph_agentic_rag.ipynb b/cookbook/langgraph_agentic_rag.ipynb
index 948158611dc..cd2bf532a70 100644
--- a/cookbook/langgraph_agentic_rag.ipynb
+++ b/cookbook/langgraph_agentic_rag.ipynb
@@ -79,6 +79,17 @@
     "tool_executor = ToolExecutor(tools)"
    ]
   },
+  {
+   "cell_type": "markdown",
+   "id": "168152fc",
+   "metadata": {},
+   "source": [
+    "📘 **Note on `SystemMessage` usage with LangGraph-based agents**\n",
+    "\n",
+    "When constructing the `messages` list for an agent, you *must* manually include any `SystemMessage`s.\n",
+    "Unlike some agent executors in LangChain that set a default, LangGraph requires explicit inclusion."
+   ]
+  },
   {
    "cell_type": "markdown",
    "id": "fe6e8f78-1ef7-42ad-b2bf-835ed5850553",