diff --git a/tests/test_litellm/llms/anthropic/experimental_pass_through/messages/test_anthropic_experimental_pass_through_messages_handler.py b/tests/test_litellm/llms/anthropic/experimental_pass_through/messages/test_anthropic_experimental_pass_through_messages_handler.py
index 07607d75bf5..1e1adbf04d8 100644
--- a/tests/test_litellm/llms/anthropic/experimental_pass_through/messages/test_anthropic_experimental_pass_through_messages_handler.py
+++ b/tests/test_litellm/llms/anthropic/experimental_pass_through/messages/test_anthropic_experimental_pass_through_messages_handler.py
@@ -220,11 +220,19 @@ async def test_anthropic_messages_sanitizes_tool_use_ids_before_dispatch():
     assert msgs[0]["content"][0]["id"] == "functions.Bash:0"
 
 
-@pytest.mark.asyncio
-async def test_anthropic_messages_keeps_tool_use_ids_for_non_anthropic_api_base():
-    from litellm.llms.anthropic.experimental_pass_through.messages import handler
+_ANTHROPIC_MESSAGES_OK = {
+    "id": "msg_test",
+    "type": "message",
+    "role": "assistant",
+    "model": "claude-sonnet-4-5-20250929",
+    "content": [{"type": "text", "text": "ok"}],
+    "stop_reason": "end_turn",
+    "usage": {"input_tokens": 1, "output_tokens": 1},
+}
 
-    msgs = [
+
+def _tool_use_replay_messages():
+    return [
         {
             "role": "assistant",
             "content": [
@@ -237,29 +245,38 @@ async def test_anthropic_messages_keeps_tool_use_ids_for_non_anthropic_api_base(
             ],
         }
     ]
+
+
+def _capturing_anthropic_client():
     captured = {}
 
-    def fake_handler(*args, **kwargs):
-        captured["messages"] = kwargs.get("messages")
-        return "stub"
+    def capture_upstream(request: httpx.Request) -> httpx.Response:
+        captured["body"] = json.loads(request.content)
+        return httpx.Response(200, json=_ANTHROPIC_MESSAGES_OK, request=request)
 
-    fake_loop = MagicMock()
-    fake_loop.run_in_executor = lambda _e, func: _async_return(func())
+    upstream = AsyncHTTPHandler()
+    upstream.client = httpx.AsyncClient(transport=httpx.MockTransport(capture_upstream))
+    return captured, upstream
 
-    with (
-        patch.object(handler, "anthropic_messages_handler", side_effect=fake_handler),
-        patch("asyncio.get_event_loop", return_value=fake_loop),
-    ):
-        await handler.anthropic_messages(
-            max_tokens=100,
-            messages=msgs,
-            model="anthropic/claude-sonnet-4-5-20250929",
-            custom_llm_provider="anthropic",
-            api_key="k",
-            api_base="http://127.0.0.1:8000/v1",
-        )
 
-    assert captured["messages"][0]["content"][0]["id"] == "functions.Bash:0"
+@pytest.mark.asyncio
+async def test_anthropic_messages_keeps_tool_use_ids_for_non_anthropic_api_base():
+    from litellm.llms.anthropic.experimental_pass_through.messages import handler
+
+    msgs = _tool_use_replay_messages()
+    captured, upstream = _capturing_anthropic_client()
+
+    await handler.anthropic_messages(
+        max_tokens=100,
+        messages=msgs,
+        model="anthropic/claude-sonnet-4-5-20250929",
+        custom_llm_provider="anthropic",
+        api_key="k",
+        api_base="http://127.0.0.1:8000/v1",
+        client=upstream,
+    )
+
+    assert captured["body"]["messages"][0]["content"][0]["id"] == "functions.Bash:0"
     assert msgs[0]["content"][0]["id"] == "functions.Bash:0"
 
 
@@ -267,41 +284,19 @@ async def test_anthropic_messages_keeps_tool_use_ids_for_non_anthropic_api_base(
 async def test_anthropic_messages_sanitizes_azure_ai_model_prefix_without_provider():
     from litellm.llms.anthropic.experimental_pass_through.messages import handler
 
-    msgs = [
-        {
-            "role": "assistant",
-            "content": [
-                {
-                    "type": "tool_use",
-                    "id": "functions.Bash:0",
-                    "name": "Bash",
-                    "input": {},
-                }
-            ],
-        }
-    ]
-    captured = {}
+    msgs = _tool_use_replay_messages()
+    captured, upstream = _capturing_anthropic_client()
 
-    def fake_handler(*args, **kwargs):
-        captured["messages"] = kwargs.get("messages")
-        return "stub"
+    await handler.anthropic_messages(
+        max_tokens=100,
+        messages=msgs,
+        model="azure_ai/claude-sonnet-4-5",
+        api_key="k",
+        api_base="https://myres.services.ai.azure.com/anthropic",
+        client=upstream,
+    )
 
-    fake_loop = MagicMock()
-    fake_loop.run_in_executor = lambda _e, func: _async_return(func())
-
-    with (
-        patch.object(handler, "anthropic_messages_handler", side_effect=fake_handler),
-        patch("asyncio.get_event_loop", return_value=fake_loop),
-    ):
-        await handler.anthropic_messages(
-            max_tokens=100,
-            messages=msgs,
-            model="azure_ai/claude-sonnet-4-5",
-            api_key="k",
-            api_base="https://myres.services.ai.azure.com/anthropic",
-        )
-
-    assert captured["messages"][0]["content"][0]["id"] == "functions_Bash_0"
+    assert captured["body"]["messages"][0]["content"][0]["id"] == "functions_Bash_0"
     assert msgs[0]["content"][0]["id"] == "functions.Bash:0"