On 7/22/2026 between 6pm and 7pm PST, I was driving my Tesla Model Y on I-405 southbound in Orange County, CA, between the Westminster Blvd exit and Exit 73, with Full Self-Driving (Supervised) engaged. The incident occurred at an express lane ingress/egress transition zone where a physical barrier separates the express and general-purpose lanes. While in FSD mode, the vehicle initiated a lane change on its own. During the lane change, the FSD system misjudged the lane boundary and steered the vehicle into the lane divider/barrier. The vehicle struck the divider on the front right side. The failed system is the FSD/automated steering and lane change function. No forward collision warning sounded and no automatic emergency braking activated before impact with the fixed barrier. There were no warning lamps, alerts, or symptoms prior to the failure; the system initiated and executed the lane change without indicating any problem. The impact damaged the front right body panel, front right bumper area, and the right headlight. My safety and the safety of vehicles in adjacent lanes was put at risk, as the collision occurred at roadway speed during an automated maneuver I did not initiate. Had the divider been a vehicle or a pedestrian work zone, the outcome could have been far more severe. All FSD telemetry, camera footage, and vehicle data from the incident should be available from the manufacturer, and I have requested the vehicle data report from Tesla. The vehicle is availab