Surging interest in artificial intelligence has generated huge gains for tech stocks across the world this year. But with the stock market hitting new highs, there are growing concerns that we might be in the midst of an AI bubble. In this bonus edition of the Fidelity Answers podcast Patrick Graham puts four possible flaws in the AI investment case to Terence Tsai, one of Fidelity's portfolio managers who has invested strongly in the boom and therefore one of the people looking hardest for evidence of when it ends.