[BUG] `paint` is not working with `openrouter` provider

[fguillen]

Basic checks

• I searched existing issues - this hasn't been reported
• I can reproduce this consistently
• This is a RubyLLM bug, not my application code

What's broken?

In my application I use openrouter as provider, when I use the paint method I receive a:

 status=405,
 reason_phrase="Method Not Allowed",

In the response

How to reproduce

RubyLLM.configure do |config|
  config.openrouter_api_key = ENV["OPENROUTER_API_KEY"]
  config.default_image_model = "openai/gpt-5-image"
end
    
RubyLLM.paint("Generate an image of a dog in rollers")

The request is made to:

https://openrouter.ai/api/v1/images/generations

And this URL doesn't exist in the API.

Looking in the OpenRouter API doc I see the image generation uses the same endpoint that the chat:

https://openrouter.ai/api/v1/chat/completions

Expected behavior

The DSL uses the proper openrouter endpoint and generates the image

What actually happened

Response error

Environment

• Ruby version: 3.3.4
• RubyLLM version: 1.9.0
• Provider: OpenRouter
• OS: MacOS