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OpenAI filed confidential IPO paperwork on May 22, 2026, with Goldman Sachs and Morgan Stanley leading a process targeting a September 2026 public debut; pre-filing reports and social commentary now cite a valuation target exceeding $1 trillion, up from the $852 billion private-round figure [9][10][11]. The filing came four days after a federal jury unanimously rejected Elon Musk's lawsuit over OpenAI's nonprofit-to-for-profit conversion — but Musk immediately announced he would appeal to the Ninth Circuit, keeping the legal challenge alive [33][6]. Compounding the competitive picture, OpenAI co-founder Andrej Karpathy publicly joined Anthropic the day after the verdict, delivering a high-profile talent signal to a race that industry analysts are still treating as genuinely open [20][22]. California's attorney general maintains an active investigation into OpenAI's nonprofit conversion that the jury verdict did not resolve [31][32].

OpenAI's IPO marks its definitive shift from a nonprofit-origin research lab to a publicly traded technology company at near-trillion-dollar scale, imposing governance and competitive scrutiny that private backers never applied. The combination of Musk's active appeal, the California AG's unresolved investigation, and Karpathy's move to Anthropic means OpenAI enters the public markets with its foundational legal narrative and competitive standing still actively contested — a meaningful test of whether the IPO story holds under public scrutiny.

On May 18, 2026, a federal jury delivered a unanimous verdict rejecting all three of Elon Musk's claims in Musk v. Altman, the lawsuit alleging that OpenAI and Sam Altman betrayed the company's nonprofit mission when they created a for-profit arm [1][2][3]. The jury's reasoning was procedural rather than substantive: Musk was found to have been aware of OpenAI's restructuring plans as early as 2021, meaning he missed the three-year statute of limitations and waited too long to sue [4][5]. All defendants — Sam Altman, Greg Brockman, Microsoft, and OpenAI — were found not liable. Within hours of the verdict, Musk announced he would appeal to the Ninth Circuit, ensuring the legal challenge would continue even as OpenAI accelerated toward its IPO [6][7][8]. The substantive question of whether OpenAI's conversion was mission-consistent was never adjudicated on the merits.

Four days after the verdict, on May 22, OpenAI filed confidential IPO paperwork with Goldman Sachs and Morgan Stanley serving as lead underwriters, targeting a September 2026 public debut [9][10][11]. Multiple major outlets — Bloomberg, the Wall Street Journal, Reuters, the New York Times, and TechCrunch — had reported the filing was imminent in the days prior [12][13][14]. The valuation target cited in pre-filing reports rose above $1 trillion, a step up from the $852 billion figure associated with OpenAI's most recent private funding round [10][15]. SpaceX filed its own S-1 on the same day, framing May 22 as the opening of a major AI-adjacent IPO wave [16][17]. OpenAI employees had already been cashing out shares in advance of the public offering, with hundreds reportedly netting tens of millions of dollars each in secondary transactions [18][19].

The day after the Musk verdict, Andrej Karpathy — an OpenAI founding team member who also led Tesla's Autopilot effort, briefly returned to OpenAI, and then departed to start an education venture — publicly announced he had joined Anthropic [20][21][22]. His hire drew immediate commentary as a symbolic competitive event: Karpathy is among the most recognized researchers in applied AI, and his choice of Anthropic was widely read as a talent signal about where frontier AI opportunity is perceived to lie [23][24]. The announcement landed at exactly the moment that SemiAnalysis analysts were debating whether OpenAI's recent product releases — Codex and GPT-5.5 — represented a genuine recovery from a period of competitive weakness relative to Anthropic; Karpathy's move complicated the 'comeback' framing without settling the underlying model-capability question [25][26].

One governance overhang the jury verdict did not extinguish is California's attorney general investigation into OpenAI's nonprofit-to-for-profit conversion. A coalition including the San Francisco Foundation and Public Citizen formally requested AG action to protect OpenAI's charitable assets, and civil society groups have continued to press the AG's office even after an initial deal between OpenAI and the AG was struck — a deal that critics argue contains significant holes [27][28][29][30]. Analysis published through mid-2025 argued the investigation must continue, and the investigation remained active as OpenAI moved toward the IPO filing [31][32]. Public-market investors will encounter this governance history in the prospectus; the jury's procedural ruling, which left the substantive mission-betrayal claims unadjudicated, may provide less reassurance than the headline verdict implies.