Troubleshooting Nano Banana errors

For parameter values, see Nano Banana text to image & sizes.

Start from the symptom

400 Request contains an invalid argument

{
  "error": {
    "code": 400,
    "message": "Request contains an invalid argument.",
    "status": "INVALID_ARGUMENT"
  }
}

This error does not say which parameter is at fault. In our tests, all of the following return it:

How to narrow it down: retry without imageConfig first; if the image generates, the problem is the aspect ratio or resolution, so add them back one at a time to find it.

Wrong aspect ratio or resolution

Check the actual width and height of the output image first, then go through this table:

Correct form:

{
  "contents": [{ "parts": [{ "text": "..." }] }],
  "generationConfig": {
    "responseModalities": ["IMAGE"],
    "imageConfig": { "aspectRatio": "9:16", "imageSize": "2K" }
  }
}

Both spellings are recognized — imageConfig / image_config and aspectRatio / aspect_ratio. In our tests, image_config: { aspect_ratio: "9:16" } correctly produced 768×1376.

No image in the response

In clients such as Cherry Studio or LobeHub, add the model as an image generation model, not a chat model.

410 model_deprecated

{
  "error": {
    "message": "Model 'google/gemini-3-pro-image-preview' is deprecated and no longer accepts requests; please switch to an active model",
    "type": "model_deprecated",
    "code": 410
  }
}

Old IDs ending in -preview have been retired; use the GA IDs instead:

In the native API path, the model ID can include or omit the google/ prefix; both work in our tests.

Edited result has nothing to do with the original

To confirm the reference image was read: on the native API, check whether usageMetadata.promptTokensDetails contains an IMAGE entry; on the OpenAI-compatible API, check usage.input_tokens_details.image_tokens. We measured 1,120 tokens for one 1024×1024 reference image.

Safety blocks

When a request is blocked by the safety policy, the response contains no image, and the reason is recorded in finishReason or promptFeedback.blockReason. What each value means (per Google’s official definitions):

Your code should not assume the response always contains an image: check that candidates exists and that finishReason is STOP before reading inlineData. Field definitions: Gemini API · FinishReason .

Timeouts, 504, 524

The API is synchronous. We measured about 5 to 20 seconds at 1K and about 30 seconds at 4K, longer at peak times. The common 60-second default timeout is not enough.

• Set the client timeout to 300 seconds or more.
• Check the timeouts of intermediate proxies such as Nginx, Vercel or Cloudflare, whose defaults are often only 60 to 100 seconds.
• A 4K PNG is about 16 MB and the response body exceeds 20 MB; make sure your proxies do not truncate large responses.

If the client disconnects early, the request is still billed.

Other errors

When contacting support, include the request_id from the response and the full error message.

FAQ