diff --git a/llama_stack/providers/inline/agents/meta_reference/agent_instance.py b/llama_stack/providers/inline/agents/meta_reference/agent_instance.py
index df6c9bb36..a977b0c33 100644
--- a/llama_stack/providers/inline/agents/meta_reference/agent_instance.py
+++ b/llama_stack/providers/inline/agents/meta_reference/agent_instance.py
@@ -481,7 +481,17 @@ class ChatAgent(ShieldRunnerMixin):
                 contexts.append(raw_document_text)
 
             attached_context = "\n".join(contexts)
-            input_messages[-1].content += attached_context
+            if isinstance(input_messages[-1].content, str):
+                input_messages[-1].content += attached_context
+            elif isinstance(input_messages[-1].content, list):
+                input_messages[-1].content.append(
+                    TextContentItem(text=attached_context)
+                )
+            else:
+                input_messages[-1].content = [
+                    input_messages[-1].content,
+                    TextContentItem(text=attached_context),
+                ]
 
         session_info = await self.storage.get_session_info(session_id)
         # if the session has a memory bank id, let the memory tool use it