(Improvements) use /openai/ pass through with OpenAI Ruby for Assistants API (#8884)

* add ruby assistants testing

* _join_url_paths

* run ruby tests on ci/cd

* TestBaseOpenAIPassThroughHandler

* _join_url_paths

* fix _join_url_paths

* Install Ruby and Bundler

* Install Ruby and Bundler

litellm/proxy/pass_through_endpoints/llm_passthrough_endpoints.py

@@ -398,7 +398,7 @@ async def azure_proxy_route(
         )
     # Add or update query parameters
     azure_api_key = passthrough_endpoint_router.get_credentials(
-        custom_llm_provider="azure",
+        custom_llm_provider=litellm.LlmProviders.AZURE.value,
         region_name=None,
     )
     if azure_api_key is None:
@@ -413,6 +413,7 @@ async def azure_proxy_route(
         user_api_key_dict=user_api_key_dict,
         base_target_url=base_target_url,
         api_key=azure_api_key,
+        custom_llm_provider=litellm.LlmProviders.AZURE,
     )
 
 
@@ -435,7 +436,7 @@ async def openai_proxy_route(
     base_target_url = "https://api.openai.com/"
     # Add or update query parameters
     openai_api_key = passthrough_endpoint_router.get_credentials(
-        custom_llm_provider="openai",
+        custom_llm_provider=litellm.LlmProviders.OPENAI.value,
         region_name=None,
     )
     if openai_api_key is None:
@@ -450,6 +451,7 @@ async def openai_proxy_route(
         user_api_key_dict=user_api_key_dict,
         base_target_url=base_target_url,
         api_key=openai_api_key,
+        custom_llm_provider=litellm.LlmProviders.OPENAI,
     )
 
 
@@ -462,24 +464,19 @@ class BaseOpenAIPassThroughHandler:
         user_api_key_dict: UserAPIKeyAuth,
         base_target_url: str,
         api_key: str,
+        custom_llm_provider: litellm.LlmProviders,
     ):
         encoded_endpoint = httpx.URL(endpoint).path
-
         # Ensure endpoint starts with '/' for proper URL construction
         if not encoded_endpoint.startswith("/"):
             encoded_endpoint = "/" + encoded_endpoint
 
-        # Ensure base_target_url is properly formatted for OpenAI
-        base_target_url = (
-            BaseOpenAIPassThroughHandler._append_v1_to_openai_passthrough_url(
-                base_target_url
-            )
-        )
-
         # Construct the full target URL by properly joining the base URL and endpoint path
         base_url = httpx.URL(base_target_url)
         updated_url = BaseOpenAIPassThroughHandler._join_url_paths(
-            base_url, encoded_endpoint
+            base_url=base_url,
+            path=encoded_endpoint,
+            custom_llm_provider=custom_llm_provider,
         )
 
         ## check for streaming
@@ -505,21 +502,15 @@ class BaseOpenAIPassThroughHandler:
 
         return received_value
 
-    @staticmethod
-    def _append_v1_to_openai_passthrough_url(base_url: str) -> str:
-        """
-        Appends the /v1 path to the OpenAI base URL if it's the OpenAI API URL
-        """
-        if base_url.rstrip("/") == "https://api.openai.com":
-            return "https://api.openai.com/v1"
-        return base_url
-
     @staticmethod
     def _append_openai_beta_header(headers: dict, request: Request) -> dict:
         """
         Appends the OpenAI-Beta header to the headers if the request is an OpenAI Assistants API request
         """
-        if RouteChecks._is_assistants_api_request(request) is True:
+        if (
+            RouteChecks._is_assistants_api_request(request) is True
+            and "OpenAI-Beta" not in headers
+        ):
             headers["OpenAI-Beta"] = "assistants=v2"
         return headers
 
@@ -535,17 +526,31 @@ class BaseOpenAIPassThroughHandler:
         )
 
     @staticmethod
-    def _join_url_paths(base_url: httpx.URL, path: str) -> httpx.URL:
+    def _join_url_paths(
+        base_url: httpx.URL, path: str, custom_llm_provider: litellm.LlmProviders
+    ) -> str:
         """
         Properly joins a base URL with a path, preserving any existing path in the base URL.
         """
+        # Join paths correctly by removing trailing/leading slashes as needed
         if not base_url.path or base_url.path == "/":
             # If base URL has no path, just use the new path
-            return base_url.copy_with(path=path)
+            joined_path_str = str(base_url.copy_with(path=path))
+        else:
+            # Otherwise, combine the paths
+            base_path = base_url.path.rstrip("/")
+            clean_path = path.lstrip("/")
+            full_path = f"{base_path}/{clean_path}"
+            joined_path_str = str(base_url.copy_with(path=full_path))
 
-        # Join paths correctly by removing trailing/leading slashes as needed
-        base_path = base_url.path.rstrip("/")
-        clean_path = path.lstrip("/")
-        full_path = f"{base_path}/{clean_path}"
+        # Apply OpenAI-specific path handling for both branches
+        if (
+            custom_llm_provider == litellm.LlmProviders.OPENAI
+            and "/v1/" not in joined_path_str
+        ):
+            # Insert v1 after api.openai.com for OpenAI requests
+            joined_path_str = joined_path_str.replace(
+                "api.openai.com/", "api.openai.com/v1/"
+            )
 
-        return base_url.copy_with(path=full_path)
+        return joined_path_str