Merge pull request #26675 from BerriAI/litellm_/zen-snyder-4c197e

fix(vertex): preserve items on array branches in anyOf with null + de-flake test

litellm/llms/vertex_ai/common_utils.py

@@ -597,7 +597,14 @@ def process_items(schema, depth=0):
             f"Max depth of {DEFAULT_MAX_RECURSE_DEPTH} exceeded while processing schema. Please check the schema for excessive nesting."
         )
     if isinstance(schema, dict):
-        if "items" in schema and schema["items"] == {}:
+        # Vertex requires `items` whenever `type == "array"` (even inside anyOf).
+        # Normalize: empty `items: {}` and missing-items both become {"type": "object"}.
+        type_val = schema.get("type")
+        if (
+            isinstance(type_val, str)
+            and type_val.lower() == "array"
+            and ("items" not in schema or schema.get("items") == {})
+        ):
             schema["items"] = {"type": "object"}
         for key, value in schema.items():
             if isinstance(value, dict):
@@ -710,14 +717,10 @@ def convert_anyof_null_to_nullable(schema, depth=0):
 
         if contains_null:
             # set all types to nullable following guidance found here: https://cloud.google.com/vertex-ai/generative-ai/docs/samples/generativeaionvertexai-gemini-controlled-generation-response-schema-3#generativeaionvertexai_gemini_controlled_generation_response_schema_3-python
+            # Empty `items: {}` on array branches is left in place; downstream
+            # process_items() converts it to {"type": "object"}, which Vertex
+            # requires whenever type == "array" (even inside anyOf).
             for atype in anyof:
-                # Remove items field if type is array and items is empty
-                if (
-                    atype.get("type") == "array"
-                    and "items" in atype
-                    and not atype["items"]
-                ):
-                    atype.pop("items")
                 atype["nullable"] = True
 
     properties = schema.get("properties", None)

tests/local_testing/test_amazing_vertex_completion.py

@@ -3493,8 +3493,14 @@ def test_litellm_api_base(monkeypatch, provider, route):
 
 
 def test_gemini_tool_calling_working_demo():
-    load_vertex_ai_credentials()
-    litellm._turn_on_debug()
+    """
+    Regression test: tool params with anyOf containing a `{"type": "array"}`
+    branch (no items field at all) must synthesize items before the request
+    is sent to Vertex (Vertex rejects array types missing items).
+    """
+    from litellm.llms.custom_httpx.http_handler import HTTPHandler
+    from litellm.llms.vertex_ai.vertex_llm_base import VertexBase
+
     args = {
         "messages": [
             {
@@ -3564,13 +3570,75 @@ def test_gemini_tool_calling_working_demo():
         ],
         "vertex_location": "global",
     }
-    response = completion(model="vertex_ai/gemini-3-flash-preview", **args)
-    print(response)
+
+    client = HTTPHandler()
+    mock_response = MagicMock()
+    mock_response.status_code = 200
+    mock_response.headers = {"Content-Type": "application/json"}
+    mock_response.json.return_value = {
+        "candidates": [
+            {
+                "content": {
+                    "role": "model",
+                    "parts": [{"text": "Hello!"}],
+                },
+                "finishReason": "STOP",
+            }
+        ],
+        "usageMetadata": {
+            "promptTokenCount": 10,
+            "candidatesTokenCount": 5,
+            "totalTokenCount": 15,
+        },
+    }
+
+    with (
+        patch.object(client, "post", return_value=mock_response) as mock_post,
+        patch.object(
+            VertexBase,
+            "_ensure_access_token",
+            return_value=("fake-token", "fake-project"),
+        ),
+    ):
+        completion(
+            model="vertex_ai/gemini-3-flash-preview",
+            client=client,
+            **args,
+        )
+
+    sent_body = mock_post.call_args.kwargs.get(
+        "json"
+    ) or mock_post.call_args.kwargs.get("data")
+    assert sent_body is not None, "expected request body to be sent"
+    if isinstance(sent_body, str):
+        sent_body = json.loads(sent_body)
+
+    function_decl = sent_body["tools"][0]["function_declarations"][0]
+    callbacks_schema = function_decl["parameters"]["properties"]["config"][
+        "properties"
+    ]["callbacks"]
+    array_branches = [
+        branch
+        for branch in callbacks_schema["anyOf"]
+        if branch.get("type", "").lower() == "array"
+    ]
+    assert array_branches, "expected an array branch in callbacks anyOf"
+    for branch in array_branches:
+        assert "items" in branch and branch["items"], (
+            f"array branch in callbacks.anyOf must include non-empty items "
+            f"(Vertex rejects array types missing items). Got: {branch}"
+        )
 
 
 def test_gemini_tool_calling_not_working():
-    load_vertex_ai_credentials()
-    litellm._turn_on_debug()
+    """
+    Regression test: tool params with anyOf containing both an empty-items
+    array branch and a null branch must serialize with items present on the
+    array branch (Vertex rejects array types missing `items`).
+    """
+    from litellm.llms.custom_httpx.http_handler import HTTPHandler
+    from litellm.llms.vertex_ai.vertex_llm_base import VertexBase
+
     args = {
         "messages": [
             {
@@ -3637,8 +3705,64 @@ def test_gemini_tool_calling_not_working():
         ],
         "vertex_location": "global",
     }
-    response = completion(model="vertex_ai/gemini-3-flash-preview", **args)
-    print(response)
+
+    client = HTTPHandler()
+    mock_response = MagicMock()
+    mock_response.status_code = 200
+    mock_response.headers = {"Content-Type": "application/json"}
+    mock_response.json.return_value = {
+        "candidates": [
+            {
+                "content": {
+                    "role": "model",
+                    "parts": [{"text": "Hello!"}],
+                },
+                "finishReason": "STOP",
+            }
+        ],
+        "usageMetadata": {
+            "promptTokenCount": 10,
+            "candidatesTokenCount": 5,
+            "totalTokenCount": 15,
+        },
+    }
+
+    with (
+        patch.object(client, "post", return_value=mock_response) as mock_post,
+        patch.object(
+            VertexBase,
+            "_ensure_access_token",
+            return_value=("fake-token", "fake-project"),
+        ),
+    ):
+        completion(
+            model="vertex_ai/gemini-3-flash-preview",
+            client=client,
+            **args,
+        )
+
+    sent_body = mock_post.call_args.kwargs.get(
+        "json"
+    ) or mock_post.call_args.kwargs.get("data")
+    assert sent_body is not None, "expected request body to be sent"
+    if isinstance(sent_body, str):
+        sent_body = json.loads(sent_body)
+
+    function_decl = sent_body["tools"][0]["function_declarations"][0]
+    callbacks_schema = function_decl["parameters"]["properties"]["config"][
+        "properties"
+    ]["callbacks"]
+    array_branches = [
+        branch
+        for branch in callbacks_schema["anyOf"]
+        if branch.get("type", "").lower() == "array"
+    ]
+    assert array_branches, "expected an array branch in callbacks anyOf"
+    for branch in array_branches:
+        assert "items" in branch and branch["items"], (
+            f"array branch in callbacks.anyOf must include non-empty items "
+            f"(Vertex rejects array types missing items). Got: {branch}"
+        )
 
 
 def test_vertex_ai_llama_tool_calling():

tests/test_litellm/llms/vertex_ai/test_vertex_ai_common_utils.py

@@ -225,7 +225,11 @@ def test_build_vertex_schema():
                     "metadata": {"type": "object"},
                     "callbacks": {
                         "anyOf": [
-                            {"type": "array", "nullable": True},
+                            {
+                                "type": "array",
+                                "items": {"type": "object"},
+                                "nullable": True,
+                            },
                             {"type": "object", "nullable": True},
                         ]
                     },
@@ -288,6 +292,43 @@ def test_process_items_basic():
     process_items(schema)
     assert schema["properties"]["nested"]["items"] == {"type": "object"}
 
+    # Vertex rejects array types missing `items` entirely (not just empty).
+    # Synthesize {"type": "object"} so the request validates.
+    schema = {"type": "array"}
+    process_items(schema)
+    assert schema["items"] == {"type": "object"}
+
+
+def test_build_vertex_schema_array_branch_missing_items_in_anyof():
+    """
+    Regression: an `anyOf` branch with `{"type": "array"}` (no items) must
+    end up with synthesized `items: {"type": "object"}` after the schema
+    transform — Vertex returns INVALID_ARGUMENT otherwise.
+    """
+    from litellm.llms.vertex_ai.common_utils import _build_vertex_schema
+
+    parameters = {
+        "properties": {
+            "callbacks": {
+                "anyOf": [
+                    {"type": "array"},
+                    {"type": "object"},
+                    {"type": "null"},
+                ]
+            }
+        },
+        "type": "object",
+    }
+
+    result = _build_vertex_schema(parameters)
+    callbacks_anyof = result["properties"]["callbacks"]["anyOf"]
+    array_branches = [b for b in callbacks_anyof if b.get("type") == "array"]
+    assert array_branches, "expected an array branch to remain after transform"
+    for branch in array_branches:
+        assert branch.get("items") == {
+            "type": "object"
+        }, f"array branch must have items synthesized; got {branch}"
+
 
 def test_vertex_ai_complex_response_schema():
     import json