Get Sigma 105mm f/1.4 DG HSM Art for Canon, Nikon, Sony mirrorless at B&H Photo.
This page assesses the Sigma 105mm f/1.4 DG HSM Art for focus shift at a distance of approximately 1.5 meters.
One might think that a “small” amount of focus shift is acceptable. But it is not—I think I at first unfairly blamed the Nikon D850 for focusing errors in the f/4 and f/5.6 images. It might well be a factor, but the dominant error seems to be the zone of sharp focus being too deep, e.g., centered inside the eyeball instead of centered on the iris of the eye. This series explores that theory, with definitive results/
The interesting 'twist' here is that Sony mirrorless cameras focus at the shooting aperture*, thus eliminating focus shift as a consideration. That, combined with the near-perfect hit rate of Sony Eye AF (see Autofocus Configuration for Sony A7R II and Siblings: Buttons and Eye AF) should prove interesting when the Sony-mount version arrives.
* This might have changed with a firmware update, and it might depend on variables such as the scene brightness—some research needed to see the current behavior in dim or bright light, and it might also depend on lens brand (Sony, Zeiss, Sigma, etc).