Erdogan has met Putin and ironed out the partition of northeastern Syria. He gets to keep everything he conquered and the rest stays with Assad. YPG retreats from a 30km strip along the border, leaving the bulk of Kurdish-populated areas. Russo-Turkish patrols guard the safe zone. The deal shows two things:
By inviting Assad the SDF have completely relinquished their sovereignty. This was why they were so relutanct to receive aid during Olive Branch. As long as Erdogan maintains good relations with Assad and Putin, YPG will no longer bother him. If, however, relations sour then he can even expect a repeat of the 90s, when Hafez sheltered Ocalan and allowed PKK to use Syria as its base of operations.
The deal was discussed with Putin, not Assad. It’s also clear who calls the shots.
For the war as a whole, peace is now closer. Once Idlib is sorted out, a simple deal with Turkey can grant Assad the whole country except for al-Tanf.