fix(responses-bridge): flatten namespace tools without recursion

Co-Authored-By: Devin AI <158243242+devin-ai-integration[bot]@users.noreply.github.com>

litellm/responses/litellm_completion_transformation/namespace_tools.py

@@ -5,7 +5,9 @@ Completions providers.
 A namespace tool is a grouping container: it carries no callable schema of its own and
 holds its callable tools under ``tools``. Chat Completions has no equivalent container,
 so the bridge replaces each namespace with the tools it contains, which then go through
-the same conversion as any top level tool.
+the same conversion as any top level tool. Namespaces are flat in practice, and a
+namespace that somehow contains another one keeps the inner container, which the
+conversion then drops as an unsupported type.
 """
 
 from collections.abc import Sequence
@@ -19,9 +21,7 @@ ResponsesAPITool: TypeAlias = FunctionToolParam | OpenAIMcpServerTool
 
 
 def flatten_namespace_tools(tools: Sequence[ResponsesAPITool]) -> tuple[ResponsesAPITool, ...]:
-    """Replace every namespace tool with its nested tools, recursively."""
+    """Replace every namespace tool with the tools it contains."""
     return tuple(
-        nested
-        for tool in tools
-        for nested in (flatten_namespace_tools(tool.get("tools") or ()) if tool.get("type") == "namespace" else (tool,))
+        nested for tool in tools for nested in (tool.get("tools") or () if tool.get("type") == "namespace" else (tool,))
     )

litellm/responses/litellm_completion_transformation/transformation.py

@@ -1324,7 +1324,7 @@ class LiteLLMCompletionResponsesConfig:
                     chat_completion_tools.append(converted)
             else:
                 _tool_type = tool.get("type")
-                if _tool_type in ("computer_use", "image_generation", "shell"):
+                if _tool_type in ("computer_use", "image_generation", "namespace", "shell"):
                     # Drop unsupported Responses-API-only tool types that have no
                     # Chat Completions equivalent. Passing them through verbatim
                     # causes providers to reject the request with "'function' is a

tests/test_litellm/responses/litellm_completion_transformation/test_litellm_completion_responses.py

@@ -1633,6 +1633,34 @@ class TestToolTransformation:
             "read_file",
         ]
 
+    def test_transform_nested_namespace_container_is_dropped(self):
+        """A namespace inside a namespace is not something clients send, but its inner
+        container must never reach the provider as a tool without a function schema."""
+        tools = [
+            {
+                "type": "namespace",
+                "name": "outer",
+                "tools": [
+                    {"type": "function", "name": "outer_tool"},
+                    {
+                        "type": "namespace",
+                        "name": "inner",
+                        "tools": [{"type": "function", "name": "inner_tool"}],
+                    },
+                ],
+            }
+        ]
+
+        (
+            result_tools,
+            _,
+        ) = LiteLLMCompletionResponsesConfig.transform_responses_api_tools_to_chat_completion_tools(
+            tools=tools
+        )
+
+        assert [tool["function"]["name"] for tool in result_tools] == ["outer_tool"]
+        assert not any(tool.get("type") == "namespace" for tool in result_tools)
+
     def test_bedrock_anthropic_drops_derived_web_search_options(self):
         """
         Regression for LIT-3858: a Responses web_search tool becomes a derived