As investors scramble to acquire shares in high-profile AI firms, Anthropic updated its website this week to warn that several private and secondary investment platforms offering access to its shares are doing so without authorization.
The company specifically named Open Doors Partners, Unicorns Exchange, Pachamama Capital, Lionheart Ventures, Hiive (for new offerings), Forge Global (for new offerings), Sydecar, and Upmarket as unauthorized entities for buying or selling its stock.
“Any sale or transfer of Anthropic stock, or any interest in Anthropic stock, offered by these firms is void and will not be recognized on our books and records,” the company’s official support page states.
In response, Forge Global claimed it was included erroneously and is working with Anthropic to correct the alert, stating they do not facilitate transactions without explicit corporate approval. Sydecar maintained it acts only in an administrative capacity and requires sponsors to attest that they have the necessary consents for any share transfers.
The update coincides with a surge in platforms offering exposure to AI companies via secondary markets, where existing shareholders sell stakes through special purpose vehicles (SPVs), tokenized securities, or secondary market holdings. Anthropic, rumored to be raising funds at a staggering $900 billion valuation, has become one of the most sought-after and "hardest to source" stocks in the private market.
The trend has even extended to crypto exchanges like OKX, which have launched pre-IPO perpetual futures—derivative instruments that track private company valuations without offering actual share ownership. By issuing this warning, Anthropic is taking a proactive stance against the proliferation of unauthorized investment vehicles to maintain strict control over its cap table.
