fix(logging): fallback to bare model name on provider mismatch in model cost lookup (closes #47675)

litellm/litellm_core_utils/litellm_logging.py

@@ -6757,7 +6757,7 @@ class StandardLoggingPayloadSetup:
             model_cost_information = StandardLoggingModelInformation(model_map_key="", model_map_value=None)
         else:
             try:
-                _model_cost_information: Final = litellm.get_model_info(
+                _model_cost_information = litellm.get_model_info(
                     model=pricing_model_name or model_cost_name,
                     custom_llm_provider=custom_llm_provider,
                     api_base=api_base,
@@ -6767,13 +6767,30 @@ class StandardLoggingPayloadSetup:
                     model_map_value=_model_cost_information,
                 )
             except Exception:
-                verbose_logger.debug(  # keep in debug otherwise it will trigger on every call
-                    "Model=%s is not mapped in model cost map. Defaulting to None model_cost_information for standard_logging_payload",
-                    model_cost_name,
-                )
-                model_cost_information = StandardLoggingModelInformation(
-                    model_map_key=model_cost_name, model_map_value=None
-                )
+                # Fallback: if provider mismatch lookup fails, try bare model name
+                _model_cost_information = None
+                if custom_llm_provider is not None:
+                    try:
+                        _model_cost_information = litellm.get_model_info(
+                            model=pricing_model_name or model_cost_name,
+                            api_base=api_base,
+                        )
+                    except Exception:
+                        _model_cost_information = None
+
+                if _model_cost_information is not None:
+                    model_cost_information = StandardLoggingModelInformation(
+                        model_map_key=model_cost_name,
+                        model_map_value=_model_cost_information,
+                    )
+                else:
+                    verbose_logger.debug(  # keep in debug otherwise it will trigger on every call
+                        "Model=%s is not mapped in model cost map. Defaulting to None model_cost_information for standard_logging_payload",
+                        model_cost_name,
+                    )
+                    model_cost_information = StandardLoggingModelInformation(
+                        model_map_key=model_cost_name, model_map_value=None
+                    )
         return model_cost_information
 
     @staticmethod

tests/unit/litellm_core_utils/test_model_cost_information.py

@@ -0,0 +1,52 @@
+"""
+Regression test for Issue #47675:
+Verifies that get_model_cost_information falls back to bare model name lookup
+when deployment custom_llm_provider does not match the provider key in model pricing map.
+"""
+import pytest
+import litellm
+from litellm.litellm_core_utils.litellm_logging import StandardLoggingPayloadSetup
+from litellm.types.utils import ModelResponse
+
+
+def test_cross_key_provider_mismatch_fallback():
+    """
+    Test that when custom_llm_provider='anthropic' is used with a model priced under
+    another provider (e.g., 'tencent/deepseek-v4.1-flash'), the fallback populates
+    model_map_value instead of silently returning None ($0 spend).
+    """
+    setup = StandardLoggingPayloadSetup()
+    model = "tencent/deepseek-v4.1-flash"
+    mock_response = ModelResponse(model=model)
+
+    info = setup.get_model_cost_information(
+        base_model=model,
+        custom_pricing=False,
+        custom_llm_provider="anthropic",
+        init_response_obj=mock_response,
+    )
+
+    assert info.get("model_map_key") == model
+    assert info.get("model_map_value") is not None
+    assert info["model_map_value"].get("litellm_provider") == "tencent"
+    assert info["model_map_value"].get("input_cost_per_token") == 3e-07
+
+
+def test_unmapped_model_safely_returns_none():
+    """
+    Test that an unknown model that does not exist in the pricing map
+    safely returns model_map_value=None without raising unhandled exceptions.
+    """
+    setup = StandardLoggingPayloadSetup()
+    fake_model = "fake_provider/completely_non_existent_model_xyz"
+    mock_response = ModelResponse(model=fake_model)
+
+    info = setup.get_model_cost_information(
+        base_model=fake_model,
+        custom_pricing=False,
+        custom_llm_provider="anthropic",
+        init_response_obj=mock_response,
+    )
+
+    assert info.get("model_map_key") == fake_model
+    assert info.get("model_map_value") is None