We are experiencing a reproducible image-generation issue using Google image-generation models.
The issue occurs not only through Replicate, but also through a Vertex AI API access path.
The issue started only after the transition from the previous Preview version to the current Image version.
It affects both:
- Gemini 3 Pro Image
- Gemini 3.1 Flash Image
The problem appears specifically when generating images at 4K resolution.
When one or more reference images have a bright, light, or white background, the generated result may contain large repeating square texture patches across the background. Instead of producing a uniform white background, the model creates tiled, fabric-like or paper-like patterns with visible repetition and soft boundaries between the patches.
The main product is often generated correctly, while the background around it is corrupted.
We did not observe this behavior with the previous Preview version. The issue began only after switching from Preview to Image.
This behavior appears regardless of whether the output format is set to PNG or JPG/JPEG.
Expected result
A product image with a clean, flat and uniform white background, without textures, panels, tiles, repeated patterns or additional background elements.
Actual result
At 4K resolution, the generated image contains large repeating background tiles. Similar texture patches are duplicated across the image, especially in areas that should be plain white.
Conditions under which the issue occurs
- Access path / provider:
- Replicate
- Vertex AI API
- Model family affected:
- Gemini 3 Pro Image
- Gemini 3.1 Flash Image
- Input type: image-to-image generation using reference images
- Reference-image background: usually bright, light grey, or white
- Requested background: plain white
- Output resolution: 4K
- Output format: PNG and JPG/JPEG both affected
- Aspect ratio: 1:1
- Fallback model: disabled (where applicable)
Reproduction code
import Replicate from "replicate";
const replicate = new Replicate();
const output = await replicate.run(
"google/nano-banana-pro",
{
input: {
allow_fallback_model: false,
aspect_ratio: "1:1",
image_input: [
"https://api.replicate.com/v1/files/MTFmYzdmYjEtMDI0NC00NmFmLWI4ZmEtYjA4M2JhMTQ3NDJl.jpg"
],
output_format: "png",
prompt: "create a new design of this shoe, plain white background",
resolution: "4K",
safety_filter_level: "block_only_high"
}
}
);
console.log(output);
Steps to reproduce
- Use a shoe or product reference image with a bright or white background.
- Run image-to-image generation through the Replicate API.
- Use the model endpoint
google/nano-banana-pro. - Set
resolutionto"4K". - Request a plain white background.
- Inspect the generated background.
Additional observations
- The issue is reproducible through Replicate and also through a Vertex AI API access path.
- This suggests that the problem may not be limited to Replicate-side processing.
- The artifact is strongly associated with 4K generation.
- The same workflow did not produce these tiled background artifacts with the previous Preview version.
- Bright or white areas in the reference image appear to increase the likelihood of the problem.
- Prompting the model more explicitly for a uniform white background does not reliably prevent the artifact.
- The issue occurs regardless of whether the output is requested as PNG or JPG/JPEG.
- The repeated patches suggest a possible issue in the 4K upscaling, tiling, outpainting, or high-resolution decoding pipeline.
Regression information
This appears to be a regression introduced after the transition from the previous Preview model/API version to the current Image version.
Request
Please investigate whether the 4K generation pipeline is incorrectly applying tiled texture synthesis to bright or white background regions.
