The AI stock market has experienced an extreme cycle of panic selling and frenzied buying within just two weeks, with hundreds of billions of dollars flowing rapidly in and out as narratives shift, leaving investors exhausted.

Over the past two weeks, AI-related stocks have staged a dizzying rollercoaster ride 鈥?first suffering a heavy blow after industry leaders called for slowing down AI development, with the Nasdaq 100 shedding more than $600 billion in market value over two days; then, a surge in popularity for Meta's personal assistant triggered market euphoria, tech stocks rebounded strongly, and the Nasdaq 100 recovered a cumulative $3 trillion in market value from its September 15 low to the weekend, setting its first record high since early June.

According to a September 27 Bloomberg report, the pendulum of sentiment has swung violently between two extremes: "AI will destroy humanity" and "AI will help you cancel unwanted subscriptions." Rhys Williams, chief strategist at Wayve Capital Management, said bluntly: "The magnitude of the swings in both directions is astonishing and simply cannot be explained from a fundamental perspective." Nancy Tengler, CEO of Laffer Tengler Investments, summed it up: "This is a narrative-driven market, and the narrative switches every other week."

Panic: One Article Triggers $600 Billion Selloff

The trigger for this round of violent swings was an article published on September 12 by Anthropic CEO Dario Amodei.

In the article, Amodei called for slowing the pace of developing frontier AI models, a move quickly endorsed by OpenAI CEO Sam Altman and SpaceX CEO Elon Musk, further reinforcing market concerns about the existential risks of AI.

The market reaction was almost immediate. On the first trading day after Amodei's article was published, AI infrastructure stocks were hit by concentrated selling 鈥?investors feared that if development were put on hold, demand for computing equipment would shrink accordingly.

The Nasdaq 100 fell 1.5% between September 14 and 15, with individual stocks such as CoreWeave and Lam Research each dropping more than 9%, erasing a combined market value of over $600 billion in two days.

Greed: Meta's "Muse" Ignites a Rebound, $3 Trillion Roars Back

However, panic quickly dissipated last week. The explosive popularity of Meta's personal assistant Muse became the new catalyst for a reversal in market sentiment.

Meta's stock surged 11% in a single day on Monday, putting the parent company of Facebook and Instagram on track for its best monthly performance in more than a decade 鈥?after the stock had long been under pressure from market doubts about whether its massive AI investments could be monetized.

The AI chip and semiconductor sector celebrated in tandem: Arm Holdings soared 17% in a single day, Intel and AMD each rose more than 9%, and the Philadelphia Semiconductor Index (SOX) gained a cumulative 6% from Monday to Tuesday. By Friday, September 25, the Nasdaq 100 had recovered a cumulative $3 trillion in market value from its September 15 low.

At the same time, improvements in AI capabilities also triggered another wave of selling in "victim" stocks. The market expects AI agents to significantly replace human labor in areas such as price comparison, trip booking, and customer service, with companies relying on subscription fees and bargaining models bearing the brunt: insurer Allstate fell 8.9% last week, cable operator Charter Communications plunged 12%, and Planet Fitness dropped 14%.

History Repeats: Violent Sentiment Swings Are Not New

Rapidly shifting market sentiment is nothing new for a market that has been AI-driven for nearly four years.

In early 2025, the emergence of Chinese AI model DeepSeek triggered a stampede in semiconductor stocks, with Nvidia plunging 17% in a single day. Earlier this year, Anthropic's release of a new AI tool similarly triggered widespread selling from SaaS companies to asset management institutions.

Although the panic at the time proved to be exaggerated in hindsight, AI's importance to the market and the economy has only grown, with tech giants and AI startups continuing to expand their investment scale, making investors increasingly nervous.

The volatility in the semiconductor sector illustrates the point best. The SOX index doubled cumulatively from the start of the year to June 22, then plunged 29% before its July 29 low. Despite some rebound since, the index remains 13% below its June high.

In addition, persistently rising interest rates are driving up AI development costs, and data centers are facing increasingly strong social backlash 鈥?these are additional risks that investors must weigh beyond the AI spending narrative.

Valuation Pullback: Crisis or Opportunity?

The sharp selloff has pushed some AI stocks' valuations back to relatively reasonable levels, giving rise to divergent views.

JoAnne Feeney, portfolio manager at Advisors Capital Management, takes an optimistic stance. "You don't have to believe this growth rate will continue for five years to hold stocks like Nvidia or Broadcom, because their valuations have already fallen significantly," said Feeney, whose firm holds shares in both companies. "We are likely on the eve of renewed interest in the core beneficiaries of AI infrastructure."

According to Bloomberg data, Nvidia's recent valuation has fallen to its lowest level in more than a decade 鈥?its forward price-to-earnings ratio based on expected profits over the next 12 months is below 17 times, just half of its peak in 2025.

However, Daniel Pilling, portfolio manager at Sands Capital Management, remains cautious.

"We manage this position with great humility, because no one knows where this technology is headed, and overall, I think the market's sentiment toward AI is perhaps more one of concern than the optimism seen in May and June."

Tengler believes that this widespread skepticism is actually a sign of a healthy market. "What you don't want to see is euphoria, like during the internet bubble in the late 1990s," she said.

Investors will receive new key signals this week. Memory chip maker Micron Technology will report earnings after the close on Wednesday, giving the market the latest reference point on the outlook for AI spending.

But analysts believe that regardless of the earnings results, the violent swings in market sentiment are unlikely to subside. Bill Mann, chief investment strategist and portfolio manager at Motley Fool Asset Management (managing approximately $2.7 billion in assets), said bluntly:

"It's easy to focus on the 'AI doom' theory, and it's equally easy to focus on the 'AI creation' theory. This will be a reality we have to face in the market for a long time to come."