fix(router): propagate custom cost_per_token from db model_info in fallback path (#25888)

litellm/router.py

@@ -8087,14 +8087,16 @@ class Router:
                 # Get mode from database model_info if available, otherwise default to "chat"
                 db_model_info = model.get("model_info", {})
                 mode = db_model_info.get("mode", "chat")
+                input_cost_per_token = db_model_info.get("input_cost_per_token")
+                output_cost_per_token = db_model_info.get("output_cost_per_token")
 
                 model_info = ModelMapInfo(
                     key=model_group,
                     max_tokens=None,
                     max_input_tokens=None,
                     max_output_tokens=None,
-                    input_cost_per_token=None,
-                    output_cost_per_token=None,
+                    input_cost_per_token=input_cost_per_token,
+                    output_cost_per_token=output_cost_per_token,
                     litellm_provider=llm_provider,
                     mode=mode,
                     supported_openai_params=supported_openai_params,

tests/test_litellm/test_router.py

@@ -1078,6 +1078,69 @@ def test_cached_get_model_group_info():
     assert result5 is result6
 
 
+def test_model_group_info_cost_from_db_model_info():
+    """
+    When get_deployment_model_info fails (model_info is None fallback),
+    input_cost_per_token and output_cost_per_token should be read from db model_info.
+    """
+    from unittest.mock import patch
+
+    router = litellm.Router(
+        model_list=[
+            {
+                "model_name": "my-custom-model",
+                "litellm_params": {
+                    "model": "openai/my-custom-model",
+                    "api_key": "fake",
+                    "api_base": "https://my-custom-endpoint.com",
+                },
+                "model_info": {
+                    "input_cost_per_token": 0.0001,
+                    "output_cost_per_token": 0.0002,
+                },
+            },
+        ]
+    )
+
+    with patch.object(
+        router, "get_deployment_model_info", side_effect=Exception("not found")
+    ):
+        result = router._cached_get_model_group_info("my-custom-model")
+        assert result is not None
+        assert result.input_cost_per_token == 0.0001
+        assert result.output_cost_per_token == 0.0002
+
+
+def test_model_group_info_cost_none_when_db_model_info_has_no_cost():
+    """
+    When get_deployment_model_info fails and db model_info has no cost fields,
+    input/output_cost_per_token should be None.
+    """
+    from unittest.mock import patch
+
+    router = litellm.Router(
+        model_list=[
+            {
+                "model_name": "my-custom-model-no-cost",
+                "litellm_params": {
+                    "model": "openai/my-custom-model-no-cost",
+                    "api_key": "fake",
+                    "api_base": "https://my-custom-endpoint.com",
+                },
+                "model_info": {},
+            },
+        ]
+    )
+
+    with patch.object(
+        router, "get_deployment_model_info", side_effect=Exception("not found")
+    ):
+        result = router._cached_get_model_group_info("my-custom-model-no-cost")
+        assert result is not None
+        assert result.input_cost_per_token is None
+        assert result.output_cost_per_token is None
+
+
 def test_get_model_access_groups_caching():
     """
     Test that get_model_access_groups caches the no-args result