Strange behaviour

<img width="1522" height="852" alt="Image" src="https://github.com/user-attachments/assets/cc8f4cb3-8ed6-41a7-86ef-1f0f97327e78" />

Here's the default cube, as seen in obs, in spout, or in ndi. It displays properly only inside blender, in preview. Does anyone have any idea what's the problem here, and how to solve it?