Lan Wangji watches Sagramore momentarily, to be certain he doesn't need help or further guidance. Unsurprisingly, he does not. Once he is sure of that, he glances at Magnus with a tiny frown. If his hands were clean, he might go to him and squeeze his shoulder or even pull him into a hug. As it is, the best he can do is mimicking part of the exchange he just witnessed between Magnus and Sagramore, deliberately pressing his arm to Magnus' shoulder. He doesn't have the ability to make anything that he does look casual or accidental; from him, it's an obvious gesture of offered comfort.