Alphabet Inc., Google's parent company, has surpassed a 4 trillion market capitalization, joining an elite group of tech giants. This milestone is largely attributed to investor confidence in Alphabet's artificial intelligence capabilities, particularly its Gemini models, and a new multi-year deal with Apple to power Siri. The company's stock has seen significant gains, outperforming peers and reclaiming its position as the second most valuable company, behind Nvidia, surpassing Apple.