I’m trying to piece together a thought. Is it right if my employer wants to “own” the gain in productivity from these tools?
I’m being paid the same. I’m still doing 40 hours. The huge gains in productivity are not mine to enjoy, it seems.
I don't pay for the tokens I use, so why would I expect to be compensated for it?
Hell, I paid for my own programming environment (SlickEdit) years ago with my own money and still didn't expect to get paid more. I did it because it helped me deliver higher quality work more efficiently and I was proud of that.
You can absolutely capture the value of your additional productivity. Strike out on your own. Start your own company or consulting firm. That has always been the answer. Why would you think it would be any different now?
under neoliberal capitalism? no. it's late, but not too late, to join a union.
Unless the method of increasing productivity increases it disproportionately for you or you find a way to outcompete in productivity gains, I am not sure that ever happens.
Edit: To put a finer point on this, generally,employed people don't get paid more for the excess value they produce, they get paid more for for the delta in perceived value between them and the next best option to fill the position (on a grand statistical scale for careers).
* There are exceptions to this in the form of commission based jobs.