I have a Sony mirrorless APS-C sensor camera and want to buy a 50mm prime lens (75mm full frame equivalent) to shoot pictures of my cat in late dusk when she leaves the apartment.

For a couple of weeks I have tended towards the Rokinon/Samyang 50mm f/1.2 lens which provides superior image quality and an immensely fast aperture that actually provides beautiful bokeh and out of focus areas with its 9 aperture blades while still retaining exceptional sharpness and contrast of the in-focus subject; f/1.2 wasn't the result of the marketing floor for this lens.

Recently however, I thought that a Sony 50mm f/1.8 would be a better choice because unlike the Rokinon counterpart, it provides auto-focus. You can't tell cats to stand still for you to set the focus properly. You may miss good shots while you're tampering with the lens.
Furthermore, the Rokinon lens doesn't provide image stabilization, which is not an issue when using a tripod, but cats tend to move and don't leave you enough time to adjust your tripod.
Maybe at f/1.2 the Rokinon lens may get away without optical image stabilization, Sony's f/1.8 most likely will rely on it however when no flash is being used.

tl;dr: I'd like to ask you whether Sony's OSS ("optical steady shot" - lens intern optical image stabilization) is only active during shooting videos or also while capturing pictures?