Klaviyo is trading at $19.37, up 10.56%, with no verified catalyst directly accounting for the sharp gain. - On October 19, Klaviyo announced it will become the Atlassian Williams F1 Team’s official B2C CRM partner starting in 2027. Available reporting does not establish the announcement as the reason for the October 20 rise. - Market context was mixed: the Nasdaq was down 0.84% and the S&P 500 was down 0.28%; this does not explain Klaviyo’s move.