The Hawk Eye Quality from Runner's Companion says

"This quality is not cumulative with other
forms of vision magnification and is incompatible with cyber- or
bioware augmentation or replacement."

What does that mean exactly? Is a natural eye with a smartlink modification compatible? Or vision enhancement? Or is it only visual magnification augmentations that are incompatible?

I believe that any glasses mods ect would be fine. Any thing the replaces the eye wouldn't be. So additions to the eye should be OK. Though pricey in essence and nuyen.

So what does 'incompatible' mean? They lose the quality?

Likely. Though in the case of trying to use vison mag from a scope ect its more that they don't stack. But if you replace the entire eye then your freaskishly good natural eyes wont be of use.

By the exact wording of the quality it is incompatible with any vision modification. Personally, though, I would allow modifications that don't affect perception or magnify vision to work - things like flare compensation, bioware like nicitating membranes, etc. Obviously, things that replace the whole eye wouldn't work, and things that replace normal vision with computer-rendered representations (thermo, radar or ultrasound sensors) would not be compatible with Hawk Eye when active.

By the exact wording, it does not stack with other vision magnifications. It is incompatible with bioware and cyberware vision modifications. It remains compatible with vision modification from magic - from adept powers for example.

Or glasses/contacts

I'm going by the second part, where it says "incompatible with cyber- or bioware augmentation or replacement.", which would make the quality incompatible with any visual bioware or cyberware whatsoever. Which I thought was a bit harsh, and probably not intended as it was written.

It makes sense to be incompatible with cyber/bio mods; there are other qualities like this. It also makes sense to be compatible with non-magnification visual enhancements in goggles/etc.