diff --git a/tests/proxy_unit_tests/test_anthropic_messages_pre_call_hook.py b/tests/proxy_unit_tests/test_anthropic_messages_pre_call_hook.py
new file mode 100644
index 00000000000..416ae185640
--- /dev/null
+++ b/tests/proxy_unit_tests/test_anthropic_messages_pre_call_hook.py
@@ -0,0 +1,88 @@
+import asyncio
+import os
+from unittest import mock
+
+import litellm
+import pytest
+from fastapi.testclient import TestClient
+
+from litellm.integrations.custom_logger import CustomLogger
+from litellm.proxy.proxy_server import app, initialize
+
+
+EXAMPLE_ANTHROPIC_MESSAGES_RESULT = {
+    "id": "msg_test",
+    "type": "message",
+    "role": "assistant",
+    "content": [{"type": "text", "text": "Hello from LiteLLM"}],
+    "model": "gpt-3.5-turbo",
+    "stop_reason": "end_turn",
+    "usage": {"input_tokens": 5, "output_tokens": 5},
+}
+
+
+def mock_patch_anthropic_messages():
+    return mock.patch(
+        "litellm.proxy.proxy_server.llm_router.anthropic_messages",
+        return_value=EXAMPLE_ANTHROPIC_MESSAGES_RESULT,
+    )
+
+
+@pytest.fixture(scope="function")
+def fake_env_vars(monkeypatch):
+    monkeypatch.setenv("OPENAI_API_KEY", "fake_openai_api_key")
+    monkeypatch.setenv("OPENAI_API_BASE", "http://fake-openai-api-base")
+    monkeypatch.setenv("AZURE_AI_API_BASE", "http://fake-azure-api-base")
+    monkeypatch.setenv("AZURE_OPENAI_API_KEY", "fake_azure_api_key")
+    monkeypatch.setenv("AZURE_SWEDEN_API_BASE", "http://fake-azure-sweden-api-base")
+    monkeypatch.setenv("REDIS_HOST", "localhost")
+
+
+@pytest.fixture(scope="function")
+def client_no_auth(fake_env_vars):
+    from litellm.proxy.proxy_server import cleanup_router_config_variables
+
+    cleanup_router_config_variables()
+    test_dir = os.path.dirname(os.path.abspath(__file__))
+    config_path = os.path.join(test_dir, "test_configs", "test_config_no_auth.yaml")
+    asyncio.run(initialize(config=config_path, debug=True))
+    return TestClient(app)
+
+
+@mock_patch_anthropic_messages()
+def test_anthropic_messages_runs_proxy_async_pre_call_hook(
+    mock_anthropic_messages, client_no_auth
+):
+    hook_calls = []
+
+    class AnthropicMessagesPreCallHook(CustomLogger):
+        async def async_pre_call_hook(
+            self, user_api_key_dict, cache, data, call_type, **kwargs
+        ):
+            hook_calls.append(call_type)
+            data["metadata"] = {**(data.get("metadata") or {}), "source": "unit-test"}
+            return data
+
+    original_callbacks = litellm.callbacks
+    litellm.callbacks = [AnthropicMessagesPreCallHook()]
+
+    try:
+        response = client_no_auth.post(
+            "/v1/messages",
+            json={
+                "model": "gpt-3.5-turbo",
+                "max_tokens": 100,
+                "messages": [{"role": "user", "content": "hi"}],
+            },
+        )
+
+        assert response.status_code == 200
+        assert response.json()["content"][0]["text"] == "Hello from LiteLLM"
+        assert hook_calls == ["anthropic_messages"]
+        mock_anthropic_messages.assert_called_once()
+        assert (
+            mock_anthropic_messages.call_args.kwargs["metadata"]["source"]
+            == "unit-test"
+        )
+    finally:
+        litellm.callbacks = original_callbacks