Microsoft has also made selective investments in Anthropic, despite the deeper partnership with OpenAI. The investment structure is smaller and more selective, but signals that Microsoft wants optionality in case the OpenAI relationship deteriorates. The Verge reported in April 2026 that Microsoft is 'talking to use Microsoft's AI chips' with Anthropic, suggesting that the Azure-Microsoft Maicloud relationship may extend to Anthropic workloads in the future (The Verge, May 21, 2026).
What the Filing Signals
The confidential filing follows the standard SEC process for pre-IPO disclosure and allows Anthropic to begin regulatory dialog with the Securities and Exchange Commission without making the public S-1 filing visible to competitors or the broader market. The public S-1 filing is expected in late 2026 or early 2027, with the public market debut likely in 2027. The timing of the public filing will depend on market conditions, the company's financial performance through the second half of 2026, and the regulatory environment for AI companies.
The filing signals that the AI industry has reached a maturity point where the largest labs are ready to tap the public markets for the long-term capital needed to fund compute infrastructure, model training, and talent retention. Anthropic's IPO will be the first major test of public market appetite for pure-play AI lab equity. OpenAI's expected filing later in 2026 will be the second test, and the relative pricing of the two IPOs will set the valuation benchmark for the entire AI sector for years to come.
OpenAI's IPO and the Broader Context
OpenAI is also readying its own confidential IPO filing, expected to follow Anthropic's by a quarter or two (Euronews, June 3, 2026). OpenAI's last private valuation was reported at $500 billion in early 2026, lower than Anthropic's $965 billion post-money valuation from the Series H. The relative valuations reflect different revenue mix and strategic-investor dynamics: Anthropic has fewer but more strategic investors (Amazon, Google), while OpenAI has a broader mix of strategic and financial investors (Microsoft, Thrive Capital, Sequoia, Andreessen Horowitz, Khosla Ventures).
Both companies face similar disclosure challenges around the concentration of revenue from a small number of enterprise customers, the cost of compute infrastructure, and the strategic relationships with cloud providers that are also major investors. The Trump administration's support of OpenAI in the New York Times copyright lawsuit adds an additional wildcard to OpenAI's IPO timing and disclosure (The Verge, April 24, 2026).
Pentagon Dispute and Reputational Risk
Anthropic's IPO also faces reputational risk from the Pentagon dispute, where the company was declared a 'supply-chain risk' for refusing to loosen red lines around mass domestic surveillance and fully autonomous weapons, leading to a lawsuit and temporary injunction (The Verge, May 1, 2026). The Pentagon struck deals with OpenAI, Google, Microsoft, Amazon, Nvidia, Elon Musk's xAI, and the startup Reflection, allowing the agency to use their AI tools in classified settings, but explicitly excluded Anthropic despite Anthropic's previous role in handling classified materials.
Emil Michael, the Defense Department's chief technology officer, told CNBC on May 1, 2026 that Anthropic is still a supply chain risk, but called its powerful security model Mythos a 'separate national security moment,' adding that the agency has to make sure networks are hardened up because the model has capabilities that are particular to finding cyber vulnerabilities and patching them (The Verge, May 1, 2026). The dispute is likely to feature in the IPO prospectus as a risk factor, and will be scrutinized by public-market investors who are increasingly attentive to AI ethics and governance issues.
Verify current IPO filing status and Series H funding on the official Anthropic press release page at anthropic.com/news and SEC EDGAR for the public S-1 filing once available.
Fazlur Rahman
