I was headed straight but stopped so that I could move into a left turn lane. As I got into the left turn lane and was straightening up behind the person in front of me at almost a dead stop the R1S lunged forward and accelerated at a high rate of speed hitting the car in front of me (speed control issue already known on the R1T). The camera footage verifies it. No warning lights went off (forward collision avoidance, automatic emergency braking) that there was a car in front of me and to brake (normally if there is a car in front of you that close and the vehicle thinks there will be a collision the screen goes red and the letters BRAKE come up bold in black, the car will brake if it thinks you may hit something). Of course now all my side sensors donât work. I am still waiting on diagnostics from Rivian. Additionally, my seatbelt didnât lock throwing me forward. I have only had this SUV two months with 848 miles. The car in front of me had substantial damage. If anyone had been in her backseat especially a child they would have been injured. My safety was in danger with the seatbelt not locking. I am waiting on the diagnostics still from Rivian. Insurance is waiting on Rivian. There had been nothing like this prior to this incident.