Anthropic and OpenAI have each issued warnings to investors this week cautioning against purchasing their shares through unauthorised secondary market platforms, with Anthropic explicitly naming eight firms — including established players such as Forge Global and Hiive — as companies not sanctioned to offer access to their equity.
In coordinated but separate warnings issued in the week of May 12, 2026, Anthropic and OpenAI put investors on notice that special purpose vehicle (SPV)-based schemes purporting to offer access to their private shares may be invalid and potentially worthless.
Anthropic went furthest in its disclosure, identifying eight platforms by name: Open Doors Partners, Unicorns Exchange, Pachamama Capital, Lionheart Ventures, Hiive, Forge Global, Sydecar, and Upmarket. The company stated that none of these platforms are authorised to provide access to buy or sell its shares.
OpenAI issued a similar advisory, warning buyers against SPV-based share schemes, though it did not name specific platforms in its public statement.
SPVs, or special purpose vehicles, are legal entities commonly used by secondary market intermediaries to pool investor capital and gain indirect exposure to private company shares. While the structures are used legitimately in some contexts, the companies appear to be warning that schemes sold without their knowledge or consent may not confer valid equity ownership — leaving buyers with little recourse if disputes arise.
The warnings are notable for their specificity. Forge Global, one of the platforms named by Anthropic, is among the better-known secondary market operators for pre-IPO shares of high-profile technology companies and is not an obscure or fly-by-night operation. Its inclusion signals that Anthropic is drawing a firm line around even established secondary market participants that have not received explicit authorisation.
Neither Anthropic nor OpenAI has commented on whether they intend to pursue legal action against any of the named or unnamed platforms, or whether investors who have already purchased shares through such schemes have any avenue for recourse.
The announcements come as both companies continue to attract intense investor interest off the back of rapid growth in the generative AI sector. Anthropic was last publicly valued at approximately $61.5 billion following a funding round in early 2025, while OpenAI has been valued at $157 billion. Such valuations create strong demand among retail and institutional investors seeking pre-IPO exposure, fuelling a secondary market ecosystem that the companies appear increasingly determined to regulate.
Analysis
Why This Matters
- Retail investors who have already purchased shares through the named platforms face real uncertainty about whether their holdings are legally valid, potentially leaving them with significant financial losses and limited legal remedies.
- The warnings signal that Anthropic and OpenAI are tightening control over their cap tables ahead of potential IPOs, a move that could meaningfully restrict how and to whom secondary liquidity is available.
- The inclusion of established platforms like Forge Global alongside lesser-known names suggests the AI companies are prepared to draw strict lines regardless of a platform's reputation or market standing.
Background
Private secondary markets have grown substantially over the past decade as technology companies have stayed private longer, sometimes for a decade or more. Platforms like Forge Global and Hiive emerged to meet demand from early employees and investors seeking liquidity, as well as from outside investors wanting pre-IPO exposure.
SPV structures became a common workaround: a platform pools capital from multiple investors into a single entity that acquires a block of shares, giving each investor indirect economic exposure. However, this approach can clash with company shareholder agreements, which often include rights of first refusal and transfer restrictions designed to keep control over who owns equity.
Both Anthropic and OpenAI have been among the most sought-after private companies in recent memory. As their valuations soared — driven by the rapid commercialisation of generative AI — secondary market activity intensified, creating conditions ripe for both legitimate transactions and schemes operating in legal grey areas.
Key Perspectives
Anthropic and OpenAI: Both companies frame unauthorised secondary schemes as potentially harmful to investors and as violations of their shareholder agreements. By naming platforms publicly, Anthropic in particular appears to be taking an aggressive stance to deter further unauthorised activity and protect the integrity of its cap table.
Secondary Market Platforms: Firms like Forge Global have built significant businesses on the premise that secondary markets provide legitimate liquidity and access. Their inclusion on Anthropic's list will likely prompt legal and public relations responses; some may argue their structures are compliant or that they were not given adequate notice of the companies' policies.
Critics and Skeptics: Consumer advocates and securities lawyers may note that the burden of these disputes falls disproportionately on retail investors who may lack the legal sophistication to assess the validity of SPV schemes before purchasing. The warnings, while helpful, arrive after many transactions may already have occurred.
What to Watch
- Whether any of the named platforms issue formal legal challenges or public rebuttals to Anthropic's characterisation of their services as unauthorised.
- Any regulatory interest from the SEC or other securities authorities in SPV-based private share schemes targeting retail investors in AI companies.
- IPO timelines for Anthropic and OpenAI — a public listing would resolve secondary market ambiguity by creating a regulated exchange for share trading, removing the need for SPV workarounds.