Fixed in macOS 15.8.2 RC 3 (24H230). The issue is gone, and IOGPUFamily went from 104.6.6 back to 104.6.5.

Thanks. And thanks to carlosbucci for the independent confirmation and for filing FB25171330. Retested today on 15.8.2 RC 2 (24H225): unchanged. The sample above still prints hasDrawable=0 status=0x8219 glError=0x506, natively and under Rosetta. NSOpenGLView and -[NSOpenGLContext setView:] are still blank; CAOpenGLLayer and NSOpenGLLayer still render. The kernel still logs IOGPUGLDrawableUserClient::set_surface(...): Invalid surface ID = N. IOGPUFamily (104.6.6), AGXG13X (329.2) and IOSurface (372.5.4) report the same version numbers as on 24H219; only the kernel build changed. I have added this to FB25133383, together with a sysdiagnose captured right after reproducing on 24H225. I don't have a Mac running the 26.7.2 RC or the 27.2 beta. If anyone here does, the sample in the first post takes a minute to run, and a result from either build would be useful.