Gemini-3.1-flash-image-preview only generate 1k image

Gemini API
,
1

i use the follow config. whatever resolution i input,it only generate 1k image.
I found that it’s affected by the TEXT property of responseModalities and the include_thoughts property of thinking_config. When I set responseModalities: ["IMAGE"], the image is generated correctly; however, when I set responseModalities: ["IMAGE", "TEXT"], it only generates a 1K image.

payload = {

"contents": \[{

    "role": "user",

    "parts": \[{"text": "Generate an image of a cat."}\]

}\],

"generationConfig": {

    "responseModalities": \["IMAGE", "TEXT"\],

    "imageConfig": {

        "imageSize": "2K",

        "aspectRatio": "1:1"

    },

   "thinking_config": {

        "thinking_level":"high",

        "include_thoughts":True

    }

}

}