Fallback model for Nano Banana Pro

Nano Banana Pro can now fall back to a backup model (currently ByteDance Seedream 5.0 lite) when Google’s API is at capacity, instead of failing with a rate limit error.

How it works

Set allow_fallback_model to true when calling the API. If Nano Banana Pro hits a rate limit, it tries to generate the image with Seedream 5.0 lite instead. For certain inputs, for example if the aspect ratio isn’t supported, the original rate limit error is returned.

The fallback is off by default. If you don’t set allow_fallback_model, nothing changes — you’ll get a rate limit error when Google’s API is at capacity.

When the fallback is triggered, your logs still show a prediction to Nano Banana Pro. You can tell the fallback was used by checking the resolution field in your output — it says "fallback" instead of the actual resolution. You’re charged the cost of the fallback model, not Nano Banana Pro.

Limitations

Our current fallback model, Seedream 5.0 lite, doesn’t support all the same options as Nano Banana Pro:

• Seedream 5.0 lite doesn’t support 1K resolution. If you request 1K, the fallback generates at 2K and downscales the result.
• Seedream 5.0 lite doesn’t support 4K resolution. If you request 4K, the fallback won’t be used and the original rate limit error is returned.
• Seedream 5.0 lite doesn’t support the 4:5 and 5:4 aspect ratios. Requests with these ratios won’t fall back and will return the original rate limit error.