OpenAI Mania Sparks Market Frenzy: AMD Soars 25%, Nvidia Stumbles, and AI Stocks Whipsaw After DevDay Fireworks

OpenAI set off a one-two punch of market-moving news Monday, following up its blockbuster AMD partnership announcement with a high-energy Developer Day that sent ripples across tech and financial markets. The company’s earlier revelation—that it would purchase six gigawatts of AMD Instinct GPUs in a multi-year, multi-generational deal worth tens of billions of dollars—was already shaking up the semiconductor sector. But the afternoon DevDay event piled on even more momentum, unveiling a slate of new developer tools, integrations, and AI capabilities that briefly sent dozens of related stocks soaring before fast profit-taking pulled them back to earth.

CEO Sam Altman opened the San Francisco event with headline-grabbing statistics: ChatGPT now has 800 million weekly active users, 4 million developers, and processes over 8 billion tokens per minute via its API. Those figures mark a sharp jump from just a month ago, when OpenAI reported 700 million weekly users. “We’re watching something significant happen,” Altman told the audience. “Software used to take months or years to build. You saw that it can take minutes now to build with AI.” He described a future where small teams—or even individuals—could bring new software ideas to life in minutes, calling it “a transformation in how ideas become products.”

Among the headline announcements were App SDK, AgentKit, ChatKit, and Codex, four new tools designed to make it easier to embed, automate, and deploy AI across platforms. Altman said ChatKit will allow developers to “bring your own brand, your own workflows, whatever makes your product unique,” describing it as a simple, embeddable chat interface for apps and websites. AgentKit, meanwhile, was demonstrated live on stage by OpenAI engineer Christina Huang, who built a fully functioning AI agent in just eight minutes. “So in just a few minutes, we’ve designed an agent workflow, visually,” she said. “We added in some tools and widgets. We previewed it, we deployed it, we tested it, and now you all can use it.”

The crowd also got its first look at Sora 2, OpenAI’s upgraded video-generation model that blends visuals with synchronized soundscapes and ambient audio. “One of the most exciting things that we’ve been working on is how well this new model can pair sound with visuals—not just speech, but rich soundscapes,” Altman said. He also announced the launch of GPT-5 Pro, a new API model, and gpt-realtime-mini, a smaller, faster voice engine that could make conversational AI more accessible. “Personally, I think that voice is going to become one of the primary ways that people interact with AI,” he said, underscoring OpenAI’s focus on multimodal computing and natural interaction.

Throughout the event, any company name mentioned by Altman or his team saw an immediate spike in its stock price. HubSpot (HUBS) jumped as much as 7% after being cited as an early user of AgentKit to enhance its Breeze AI tool. Coursera (COUR) spiked 6% when used in a demo showing ChatGPT’s deep integration with video-based courses. Duolingo (DUOL), GitLab (GTLB), and FIG (FIG) each surged between 4–5% after shoutouts during presentations. Spotify (SPOT) rose 4% on news of its new ChatGPT connection, while Zillow (ZG) reversed early losses after its app was shown delivering live property listings. Salesforce (CRM) also advanced nearly 3% on chatter about potential Slack integrations.

However, by late afternoon, many of these stocks faded from their highs as traders rushed to book quick profits. The sharp intraday reversals suggest that even amid growing excitement around AI, investors are becoming more tactical—an early sign that enthusiasm may be peaking after nearly two years of nonstop AI-driven rallies. The “pop and fade” dynamic, now increasingly common, highlights a subtle but telling shift in sentiment: optimism remains, but blind euphoria may be giving way to a more measured, selective approach.

Meanwhile, semiconductor stocks extended their gains in the wake of OpenAI’s AMD deal—but not all benefited equally. The Philadelphia Semiconductor Index (SOX) surged more than 3% as AMD shares exploded over 25% on the partnership news. In contrast, Nvidia slipped about 1%, with investors interpreting the AMD-OpenAI alliance as a rising competitive threat to Nvidia’s longstanding dominance in AI chips. The move marked just the third time since ChatGPT’s 2022 debut that the chip index rallied more than 3% while Nvidia finished lower. For many traders, it was a sign that the AI hardware landscape—once a one-horse race—is starting to open up.

Software names also saw strong interest. Datadog (DDOG), HubSpot (HUBS), Salesforce (CRM), and Snowflake (SNOW) all climbed between 3–6%, buoyed by the takeaway that OpenAI’s innovations could complement, not cannibalize, the enterprise software ecosystem. The event did nothing to show that AI is displacing software—it’s enhancing it. That message was enough to spark a relief rally across the SaaS sector, even if some gains proved fleeting.

Altman also addressed growing concerns about froth in the AI trade. “There are many parts of AI that are kind of bubbly,” he acknowledged. “But I think this is how new tech revolutions go.” The comment drew laughter and applause, as the audience seemed to recognize the irony of a CEO whose announcements routinely send markets into a frenzy.

By the end of the day, OpenAI had once again demonstrated its power to move markets—literally by name. But the quick reversals in many AI-linked stocks serve as a warning sign that momentum, while still strong, may be entering a more mature phase. As earnings season approaches, investors may start focusing less on who gets mentioned in an OpenAI keynote—and more on who can turn that attention into real, durable revenue growth.