Meta stock falls as OpenAI ’o’ agent threatens historic rally

Investing.com — Meta Platforms (NASDAQ:META) shares fell 4.2% to $720.36 on Monday, as OpenAI’s anticipated reveal of a competing always-on AI assistant adds a fresh layer of competitive pressure to a stock that had surged roughly 30% in September alone.

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The catalyst for Monday’s decline is a September 27 report from BleepingComputer describing OpenAI’s rumored “o” assistant as a cloud-based agent capable of executing long-horizon tasks—including handling email—even after a user closes the ChatGPT app. OpenAI is expected to formally unveil the product at its DevDay 2026 keynote on Tuesday, September 29.

Meta is currently the most direct equity expression of that competitive threat. The stock’s massive September rally was built almost entirely on the breakout success of Muse, its own personal AI agent, making OpenAI’s counter-product the single most relevant risk variable for the shares.

Since its launch on September 8, Muse has accumulated over 3.4 million downloads and secured the number-one spot in the U.S. App Store, surpassing ChatGPT. That performance pushed META to an intraday high near its 52-week peak of $779.82 and prompted fresh price-target raises. Wells Fargo recently lifted its target from $640 to $796, citing Muse’s launch strength. Citi analyst Ronald Josey noted that Muse is “emerging as the centerpiece of Meta’s AI product strategy,” featuring deep integrations across shopping, travel, and productivity verticals.

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Enterprise Expansion and MongoDB Fallout

In a move to broaden its commercial footprint, Meta also announced the launch of its Meta Enterprise Platform on Monday. The new division will bring Meta’s AI models and agents—including Muse and Meta Business Agent—to enterprise customers, though Meta has not specified pricing tiers or a revenue model.

To lead the initiative, Meta appointed Chirantan “CJ” Desai as Chief Enterprise Platform Officer, reporting directly to Mark Zuckerberg. Desai previously served as CEO of MongoDB (NASDAQ:MDB), and his sudden departure sent MongoDB shares tumbling 18% to $336.79 intraday. MongoDB has since re-appointed founder Dev Ittycheria as interim CEO while it conducts a formal search for a permanent replacement.