fix(proxy): add datadog_llm_observability to /health/services allowed list (#19952)

The /health/services endpoint rejected datadog_llm_observability as an
unknown service, even though it was registered in the core callback
registry and __init__.py. Added it to both the Literal type hint and
the hardcoded validation list in the health endpoint.

litellm/proxy/health_endpoints/_health_endpoints.py

@@ -118,6 +118,7 @@ services = Union[
         "email",
         "braintrust",
         "datadog",
+        "datadog_llm_observability",
         "generic_api",
         "arize",
         "sqs"
@@ -190,6 +191,7 @@ async def health_services_endpoint(  # noqa: PLR0915
             "custom_callback_api",
             "langsmith",
             "datadog",
+            "datadog_llm_observability",
             "generic_api",
             "arize",
             "sqs"

tests/test_litellm/proxy/health_endpoints/test_health_endpoints.py

@@ -312,6 +312,43 @@ async def test_test_model_connection_loads_config_from_router():
         assert "result" in result
 
 
+@pytest.mark.asyncio
+async def test_health_services_endpoint_datadog_llm_observability():
+    """
+    Verify that 'datadog_llm_observability' is accepted as a valid service
+    by the /health/services endpoint and does not raise a 400 error.
+
+    Regression test for: https://github.com/BerriAI/litellm/issues/XXXX
+    The service was missing from the allowed services validation list.
+    """
+    from litellm.proxy.health_endpoints._health_endpoints import (
+        health_services_endpoint,
+    )
+
+    # Mock datadog_llm_observability to be in success_callback so the generic branch handles it
+    with patch("litellm.success_callback", ["datadog_llm_observability"]):
+        result = await health_services_endpoint(
+            service="datadog_llm_observability"
+        )
+
+    # Should not raise HTTPException(400) and should return success
+    assert result["status"] == "success"
+    assert "datadog_llm_observability" in result["message"]
+
+
+@pytest.mark.asyncio
+async def test_health_services_endpoint_rejects_unknown_service():
+    """
+    Verify that an unknown service name is rejected with a 400 error.
+    """
+    from litellm.proxy._types import ProxyException
+
+    with pytest.raises(ProxyException):
+        await health_services_endpoint(
+            service="totally_unknown_service_xyz"
+        )
+
+
 @pytest.fixture(scope="function")
 def proxy_client(monkeypatch):
     """