Responses API: reasoning.effort: "none" not supported for third-party models

[robertotup]

When using the Responses API with third-party models like openai/gpt-5-mini or openai/gpt-5.4, setting reasoning.effort to "none" returns a 400 error: validation failed: effort must be one of: low medium high

OpenAI's native API supports reasoning_effort: "none" for these models. Since the Responses API proxies requests to third-party providers, it would be helpful to pass through "none" as a valid value

Reproduction:

  from perplexity import Perplexity
                                   
  client = Perplexity(api_key="...")
  client.responses.create(                                                                                                                                                                              
      model="openai/gpt-5-mini",
      input="Hello",                                                                                                                                                                                    
      reasoning={"effort": "none"},                         
  )                                                                                                                                                                                                     
  # -> BadRequestError: 400 - effort must be one of: low medium high