import asyncio, os
  from dataclasses import dataclass, field
  from typing import Awaitable, Callable

  import litellm
  from litellm import Router
  from langchain_litellm import ChatLiteLLM
  from langchain_core.tools import tool
  from langchain.agents import create_agent
  from langchain.agents.middleware import AgentMiddleware, ModelRequest, ModelResponse

  litellm.drop_params = True

  router = Router(model_list=[{
      "model_name": "GPT-5.4",
      "litellm_params": {
          "model": "azure/gpt-5.4",
          "api_base": "https://<resource>.cognitiveservices.azure.com",
          "api_key": "<key>",
          "api_version": "2025-04-01-preview",
          "base_model": "gpt-5.4",
      },
  }])
  llm = ChatLiteLLM(model="GPT-5.4", streaming=True)
  llm.client = router

  @tool
  def search(query: str) -> str:
      """Search for information."""
      return "no results"

  @dataclass
  class Ctx:
      params: dict = field(default_factory=dict)

  class ParamMiddleware(AgentMiddleware):
      async def awrap_model_call(self, request: ModelRequest, handler):
          ctx = request.runtime.context
          if not ctx or not ctx.params:
              return await handler(request)
          extra = dict(request.model_settings or {})
          extra.update(ctx.params)
          return await handler(request.override(model_settings=extra))

  async def main():
      agent = create_agent(model=llm, tools=[search], middleware=[ParamMiddleware()], context_schema=Ctx)
      # Fails:
      await agent.ainvoke(
          {"messages": [{"role": "user", "content": "hi"}]},
          context=Ctx(params={"reasoning_effort": "medium"}),
      )

  asyncio.run(main())

---

litellm.APIConnectionError: AzureException APIConnectionError - api_base is required for Azure AI Studio. Please set the api_base parameter. Passed 
  api_base=None
  Traceback (most recent call last):
    File ".../litellm/responses/main.py", line 558, in aresponses
      response = await init_response
    File ".../litellm/llms/custom_httpx/llm_http_handler.py", line 2261, in async_response_api_handler
      api_base = responses_api_provider_config.get_complete_url(
    File ".../litellm/llms/azure/responses/transformation.py", line 180, in get_complete_url
      return BaseAzureLLM._get_base_azure_url(
    File ".../litellm/llms/azure/common_utils.py", line 756, in _get_base_azure_url
      raise ValueError(
  ValueError: api_base is required for Azure AI Studio. Please set the api_base parameter. Passed api_base=None