Paint's AI Image Generation Runs Local ONNX Models, Not a Remote API

This research began with my curiosity about Paint. I recently had some success looking into less-explored Windows features like UCPD and WHESCVC, and I have long known that Microsoft added a bunch of AI features into the Paint app. I do not know if anyone actually uses Paint plus AI to generate images, but I wanted to see how exactly the image generation works.

Before I started, I expected that it simply called a remote API to do the image generation. However, after I set up Binary Ninja MCP with Codex and started the analysis, I soon realized that Microsoft actually shipped local models in Windows as part of Copilot. The Paint app is sitting in the following path (yes, they are all Windows Apps now), and there are four apparent model files with the.onnxe extension.

The format of seg.onnxe was previously known, i.e., when it is XO Red with the string Microsoft_2023, it becomes a normal ONNX file. However, the format of the other three.onnxe files initially looked different. It turned out that Microsoft had not changed the algorithm, only the key.