fix: fix streaming with httpx client

prevent overwriting streams in parallel streaming calls

litellm/utils.py

@@ -32,7 +32,7 @@ from dataclasses import (
 )
 
 import litellm._service_logger  # for storing API inputs, outputs, and metadata
-from litellm.llms.custom_httpx.http_handler import HTTPHandler
+from litellm.llms.custom_httpx.http_handler import HTTPHandler, AsyncHTTPHandler
 from litellm.caching import DualCache
 from litellm.types.utils import CostPerToken, ProviderField, ModelInfo
 
@@ -10214,8 +10214,10 @@ class CustomStreamWrapper:
         custom_llm_provider=None,
         logging_obj=None,
         stream_options=None,
+        make_call: Optional[Callable] = None,
     ):
         self.model = model
+        self.make_call = make_call
         self.custom_llm_provider = custom_llm_provider
         self.logging_obj = logging_obj
         self.completion_stream = completion_stream
@@ -11766,8 +11768,20 @@ class CustomStreamWrapper:
                     custom_llm_provider=self.custom_llm_provider,
                 )
 
+    async def fetch_stream(self):
+        if self.completion_stream is None and self.make_call is not None:
+            # Call make_call to get the completion stream
+            self.completion_stream = await self.make_call(
+                client=litellm.module_level_aclient
+            )
+            self._stream_iter = self.completion_stream.__aiter__()
+
+        return self.completion_stream
+
     async def __anext__(self):
         try:
+            if self.completion_stream is None:
+                await self.fetch_stream()
             if (
                 self.custom_llm_provider == "openai"
                 or self.custom_llm_provider == "azure"