fix(deepkeep): honour empty-list replacements in _build_return_inputs

When DeepKeep returns GUARDRAIL_INTERVENED with an intentional empty
replacement (e.g. texts:[], tool_calls:[]) the previous truthiness check
treated [] as absent and forwarded the original content downstream —
a guardrail bypass for any case where the firewall wants to fully clear
a field.

Fix: replace all response_json.get(field) truthiness checks with
'is not None' comparisons so that an empty list is respected as a
deliberate replacement. Applies to texts, images, tools, tool_calls,
and the original-input fallback guards.

Adds test_apply_guardrail_honours_empty_list_replacements.

litellm/proxy/guardrails/guardrail_hooks/deepkeep/deepkeep.py

@@ -248,23 +248,29 @@ class DeepKeepGuardrail(CustomGuardrail):
         tool_calls: Any | None,
         structured_messages: Any | None,
     ) -> GenericGuardrailAPIInputs:
-        """Merge original inputs with any guardrail-modified values from the API response."""
+        """Merge original inputs with any guardrail-modified values from the API response.
+
+        Presence is checked with ``is not None`` (not truthiness) so that an
+        intentional empty-list replacement such as ``texts: []`` or
+        ``tool_calls: []`` is honoured and forwarded downstream rather than
+        silently discarded in favour of the original content.
+        """
         return_inputs = GenericGuardrailAPIInputs(texts=texts)
-        if response_json.get("texts"):
+        if response_json.get("texts") is not None:
             return_inputs["texts"] = response_json["texts"]
-        if response_json.get("images"):
+        if response_json.get("images") is not None:
             return_inputs["images"] = response_json["images"]
-        elif images:
+        elif images is not None:
             return_inputs["images"] = images
         if response_json.get("tools") is not None:
             return_inputs["tools"] = response_json["tools"]
-        elif tools:
+        elif tools is not None:
             return_inputs["tools"] = tools
-        if response_json.get("tool_calls"):
+        if response_json.get("tool_calls") is not None:
             return_inputs["tool_calls"] = response_json["tool_calls"]
-        elif tool_calls:
+        elif tool_calls is not None:
             return_inputs["tool_calls"] = tool_calls
-        if structured_messages:
+        if structured_messages is not None:
             return_inputs["structured_messages"] = structured_messages
         return return_inputs
 

tests/test_litellm/proxy/guardrails/guardrail_hooks/test_deepkeep.py

@@ -584,6 +584,57 @@ class TestDeepKeepGuardrail:
         assert result["tools"] != original_tools
         assert result["tool_calls"] != original_tool_calls
 
+    @pytest.mark.asyncio
+    async def test_apply_guardrail_honours_empty_list_replacements(self):
+        """Empty-list replacements from the API must clear the field, not fall back to originals."""
+        guardrail = DeepKeepGuardrail(
+            api_key="test-key",
+            api_base="https://test.deepkeep.ai",
+            firewall_id="fw-123",
+            guardrail_name="test",
+            event_hook="pre_call",
+        )
+
+        mock_response = Response(
+            status_code=200,
+            json={
+                "action": "GUARDRAIL_INTERVENED",
+                "blocked_reason": None,
+                # DeepKeep clears all content entirely
+                "texts": [],
+                "images": [],
+                "tools": [],
+                "tool_calls": [],
+            },
+            request=Request(
+                "POST",
+                "https://test.deepkeep.ai/v3/openai/beta/litellm_basic_guardrail_api",
+            ),
+        )
+
+        with patch.object(
+            guardrail.async_handler,
+            "post",
+            new_callable=AsyncMock,
+            return_value=mock_response,
+        ):
+            result = await guardrail.apply_guardrail(
+                inputs={
+                    "texts": ["sensitive content that should be cleared"],
+                    "tools": [{"type": "function", "function": {"name": "leak_data"}}],
+                    "tool_calls": [{"id": "call_1", "type": "function"}],
+                    "images": ["data:image/png;base64,abc"],
+                },
+                request_data={"metadata": {}},
+                input_type="request",
+            )
+
+        # Empty-list replacements must be used — not the original non-empty values
+        assert result["texts"] == []
+        assert result.get("images") == []
+        assert result.get("tools") == []
+        assert result.get("tool_calls") == []
+
     @pytest.mark.asyncio
     async def test_firewall_id_in_payload(self):
         """should include firewall_id in additional_provider_specific_params."""