Ukraine was holding 1,300 sq klm of their big prize, Kursk land, a few months ago. Russia will control that land before starting negotiations. Over the last 4 months, the area shrunk from 1,300 sq klm to about 360. In the last two days Russia has taken 100 sq klm and thousands of Ukrainian troops are trapped with no way out. Some have negotiated surrender by offering up equipment in exchange for their lives.
Once Russia clears the salient talks might begin.
Summary: Russia doesn't want to go into any negotiations with Ukraine having any leverage. So Russia will take this back before they talk.
Just some random thoughts:
You have 1,400 miles of border. Not every area is battle space. Kursk was a good move by the Ukraine. Find a weak spot and take the initiative at least in that area for a while. The Russians played it smart too. They didn't drop everything and focus on Kursk. They kept their eye on what their true objective is and dealt with Kursk as they could without sacrificing their offensive operations elsewhere.
What I find amazing in this conflict is how modern tech regards battlefield surveillance, artillery and air power (difficult to create concentration), drones, have turned the battle-space into something reminiscent of WWI, fighting in trenches spread out over long fronts.