CNBC Daily Open: U.S. stocks' gains in October owe much to AI

Traders who shorted the S&P 500 — essentially, betting that it would go down — last month were in for a rude surprise. The broad-based index ended the month 2.3% higher, defying "Octoberphobia," a term that arose because of the market crashes in 1929 and 1987 that happened during the month.

The Nasdaq Composite had an even better month than the S&P 500. The tech-heavy index climbed 4.7%, giving a hint of what helped ward off the arrival of any ill omens: the technology sector.

On Friday, Amazon shares popped 9.6% on robust growth in its cloud-computing unit and as CEO Andy Jassy pointed to "strong demand in AI and core infrastructure." The news pushed up other artificial intelligence-related stocks such as Palantir and Oracle too.

AI's ascent in the market wasn't a one-day event. In October, Nvidia, the poster child of AI, became the first company to reach a valuation of $5 trillion, with CEO Jensen Huang describing the technology as having formed a "virtuous cycle" in which usage growth will lead to an increase in investment, in turn improving AI, which will boost usage, which will… You get the idea.

Indeed, during their earnings disclosures last week, Big Tech companies announced dizzying increases in their capital expenditure, most of which will likely go toward AI infrastructure.

All that is to say that the enthusiasm over AI looks, for now, less like the immediate sugar rush of a candy bar (and the subsequent crash), and more like the sustained energy boost from a fiber-rich pumpkin.

China's factory activity slows down in October. The RatingDog China General Manufacturing PMI, compiled by S&P Global, came in at 50.6 for the month, dipping from the six-month high of 51.2 in September. Analysts polled by Reuters were expecting a reading of 50.9.

Baidu's weekly robotaxi rides hit 250,000. That's according to a spokesperson for Apollo Go, Baidu's robotaxi unit, who said the firm surpassed that figure as of Oct. 31. It's roughly the same number of weekly driverless rides as Waymo, according to report in late April.

Berkshire Hathaway operating profit rebounds. Year on year, that figure surged 34% to $13.485 billion in the third quarter. Warren Buffett's conglomerate now holds $381.6 billion in cash, the highest on record — but it isn't looking at stock buybacks yet.

U.S. markets ended Friday higher. On Sunday night stateside, futures tied to major U.S. indexes were little changed. Asia-Pacific markets rose Monday. Japan's Nikkei 225 and South Korea's Kospi were up more than 2%, as of 2 p.m. Singapore time (1 a.m. ET).

[PRO] Stocks enter November on a high. The S&P 500 is beginning November more than 16% up for the year. This week, investors should still keep an eye out for a Supreme Court case on Trump tariffs and earnings from firms like Advanced Micro Devices and Palantir.