Vistra is trading at $156.35, up 4.01%, with no clear company-specific catalyst identified for October 21. - The S&P 500 and Nasdaq were higher; broader positive sentiment may be contributing, but it is not confirmed as the direct cause. - A report noted Vistra had been trading above its 50-day moving average, but did not link that trend to the rise. - Volume details are unavailable in the provided price context.