fix(passthrough): trust the declared Google provider and Vertex-shaped paths on custom bases

The failure path only named the Google provider from the URL when the
method was one the success handler tracks or the host was a Google API
host, so a Gemini countTokens failure behind a custom GEMINI_API_BASE
(or a Vertex one behind a custom base) still logged an empty model. A
route that declares gemini or vertex_ai now wins outright, and a URL
whose path carries /projects/<p>/locations/<l>/ counts as Vertex on any
host, while a tracked method on a non-Google host no longer passes as
Vertex.

litellm/proxy/pass_through_endpoints/llm_provider_handlers/vertex_passthrough_logging_handler.py

@@ -9,7 +9,11 @@ import litellm
 from litellm._logging import verbose_proxy_logger
 from litellm.constants import VERTEX_BATCH_PREDICTION_JOBS_ROUTE
 from litellm.litellm_core_utils.litellm_logging import Logging as LiteLLMLoggingObj
-from litellm.llms.vertex_ai.common_utils import get_vertex_location_from_url, get_vertex_model_id_from_url
+from litellm.llms.vertex_ai.common_utils import (
+    get_vertex_location_from_url,
+    get_vertex_model_id_from_url,
+    get_vertex_project_id_from_url,
+)
 from litellm.llms.vertex_ai.gemini.vertex_and_google_ai_studio_gemini import (
     ModelResponseIterator as VertexModelResponseIterator,
 )
@@ -563,9 +567,16 @@ class VertexPassthroughLoggingHandler:
         return None
 
     @staticmethod
-    def is_google_ai_host(url: str) -> bool:
-        hostname: Final = urlparse(url).hostname
-        return hostname is not None and hostname.endswith((GEMINI_API_HOST_SUFFIX, VERTEX_API_HOST_SUFFIX))
+    def is_google_ai_url(url: str) -> bool:
+        parsed_url: Final = urlparse(url)
+        if parsed_url.hostname is not None and parsed_url.hostname.endswith(
+            (GEMINI_API_HOST_SUFFIX, VERTEX_API_HOST_SUFFIX)
+        ):
+            return True
+        return (
+            get_vertex_project_id_from_url(parsed_url.path) is not None
+            and get_vertex_location_from_url(parsed_url.path) is not None
+        )
 
     @staticmethod
     def custom_llm_provider_from_url(url: str) -> str:

litellm/proxy/pass_through_endpoints/pass_through_endpoints.py

@@ -732,12 +732,15 @@ def _carry_guardrail_logging_info(request_data: dict, guardrail_data: dict | Non
     metadata.setdefault("standard_logging_guardrail_information", list(entries))
 
 
+_GOOGLE_PASSTHROUGH_PROVIDERS: Final = frozenset(
+    (litellm.LlmProviders.GEMINI.value, litellm.LlmProviders.VERTEX_AI.value)
+)
+
+
 def _passthrough_google_provider(url_route: str, custom_llm_provider: str | None) -> str | None:
-    if pass_through_endpoint_logging.is_gemini_route(url_route, custom_llm_provider):
-        return "gemini"
-    if pass_through_endpoint_logging.is_vertex_route(url_route) or VertexPassthroughLoggingHandler.is_google_ai_host(
-        url_route
-    ):
+    if custom_llm_provider in _GOOGLE_PASSTHROUGH_PROVIDERS:
+        return custom_llm_provider
+    if VertexPassthroughLoggingHandler.is_google_ai_url(url_route):
         return VertexPassthroughLoggingHandler.custom_llm_provider_from_url(url_route)
     return None
 

tests/test_litellm/proxy/pass_through_endpoints/test_pass_through_endpoints.py

@@ -5821,6 +5821,10 @@ _VERTEX_SEARCH_TARGET = (
     "https://discoveryengine.googleapis.com/v1/projects/p/locations/global"
     "/dataStores/default/servingConfigs/default:search"
 )
+_RELAYED_GEMINI_COUNT_TOKENS_TARGET = "http://127.0.0.1:30732/v1beta/models/gemini-3.8-flash:countTokens"
+_RELAYED_VERTEX_COUNT_TOKENS_TARGET = (
+    "http://127.0.0.1:30732/v1/projects/p/locations/us-east5/publishers/google/models/gemini-3.8-flash:countTokens"
+)
 
 
 async def _run_passthrough_failure(
@@ -5899,6 +5903,8 @@ def _upstream_400_as_event_stream(target: str) -> httpx.Response:
         (_VERTEX_FLASH_TARGET, None, True, "vertex_ai"),
         (_GEMINI_FLASH_TARGET.replace(":generateContent", ":countTokens"), "gemini", False, "gemini"),
         (_VERTEX_FLASH_TARGET.replace(":generateContent", ":countTokens"), None, False, "vertex_ai"),
+        (_RELAYED_GEMINI_COUNT_TOKENS_TARGET, "gemini", False, "gemini"),
+        (_RELAYED_VERTEX_COUNT_TOKENS_TARGET, None, False, "vertex_ai"),
     ],
 )
 async def test_passthrough_upstream_error_logs_model_from_url(
@@ -6017,7 +6023,10 @@ async def test_passthrough_mid_stream_drop_logs_model_from_url(
             "",
             "vertex_ai",
         ),
+        ({"contents": []}, _RELAYED_GEMINI_COUNT_TOKENS_TARGET, "gemini", "gemini-3.8-flash", "gemini"),
+        ({"contents": []}, _RELAYED_VERTEX_COUNT_TOKENS_TARGET, None, "gemini-3.8-flash", "vertex_ai"),
         ({"contents": []}, "https://api.example.com/v1/models/gpt-x:countTokens", None, "", None),
+        ({"contents": []}, "https://api.example.com/v1/models/gpt-x:predict", None, "", None),
         ({"contents": []}, "https://api.example.com/v1/models/gpt-x:thing", None, "", None),
         (None, None, None, "", None),
     ],