Pass extra_body params in the request-body to vertexAI

litellm/llms/vertex_ai/gemini/transformation.py

@@ -468,6 +468,12 @@ def _transform_request_body(
             data["generationConfig"] = generation_config
         if cached_content is not None:
             data["cachedContent"] = cached_content
+
+         # Add any extra body params passed to the request body
+        extra_body = optional_params.get("extra_body", {})
+        if extra_body is not None:
+            data = {**extra_body, **data}
+
     except Exception as e:
         raise e
 

tests/test_litellm/llms/vertex_ai/test_vertex.py

@@ -1503,3 +1503,32 @@ def test_system_prompt_only_adds_blank_user_message():
     #########################################################
     assert len(data["system_instruction"]) == 1
     assert data["system_instruction"]["parts"][0]["text"] == SYSTEM_INSTRUCTION
+
+def test_extra_body_labels_added_and_existing_fields_not_overridden():
+    """
+    Test that list of parameters sent as "extra_body" are added to the request body and existing fields are not overridden.
+
+    Relevant Issue - https://github.com/BerriAI/litellm/issues/13692
+    """
+    data = _transform_request_body(
+        messages=[{"role": "system", "content": "System instructions for the model"}],
+        model="gemini-2.5-flash",
+        optional_params={
+            "extra_body": {
+                "labels": {"team": "ml"},
+                "cachedContent": "should_not_override"
+            }
+        },
+        custom_llm_provider="vertex_ai",
+        litellm_params={},
+        cached_content="pre_set",
+    )
+
+    print("Final data with extra_body: ", data)
+
+    # validate that extra_body fields are added
+    assert "labels" in data
+    assert data["labels"] == {"team": "ml"}
+
+    # validate that existing fields are not overridden
+    assert data["cachedContent"] == "pre_set"