Greentheonly got access to the manual from one of the betas which contains a section called ‘Stopping at Traffic Lights and Stop Signs’. Currently, Teslas with HW3 and FSD-preview display stop signs, traffic lights, and other road marking. However, in this new beta, when you are using Auto Steering or Traffic-Aware Cruise Control, the car actually stops for them too.
Taking another step towards complete FSD, Tesla has decided to release it in a way that still needs the user input to go through the intersection. When approaching the signal the car slows down, even if the traffic light is green, and for it to continue through the intersection you must press down on the gear lever, Autopilot stalk (S and X), or the accelerator. The notes from the manual also highlight that if you are in a turning lane you need to perform that maneuver yourself