The technology sector, as measured by the XLK ETF, experienced a significant downturn primarily driven by a historic 25.2% plunge in IBM's stock. This was triggered by an unexpected company warning that enterprise clients are shifting their IT spending from traditional software and mainframes to AI-related hardware, servers, and memory. This news created a ripple effect, negatively impacting other software companies and contributing to the sector's decline, despite strength in some semiconductor and AI-related stocks.