Anthropic is the hottest stock in private tech. It is also one of the hardest to buy, and that is exactly why the price keeps climbing.

Shares in Anthropic are changing hands on secondary markets at an implied valuation of $1.2 trillion, Business Insider reports. That is a 550% jump in a year. It puts the maker of Claude ahead of OpenAI, whose shares trade at around $908bn on the same platforms.

The figure is startling for how fast it has moved. Barely three months ago the same market valued Anthropic at $1 trillion. Its last primary round, a Series H in May, priced the company at $965bn.

The number rests on an unusual foundation. Almost nobody is selling.

Scarcity, not fundamentals

Secondary markets only work when employees or early investors are willing to part with shares. Right now they are not. Brokers describe a near-total absence of sellers, which pushes prices up on its own, with no new revenue or product to justify it.

“Anthropic is the most sought-after company the venture secondary market has ever seen,” said Javier Avalos, chief executive of the trading platform Caplight. Glen Anderson of Rainmaker Securities put it more bluntly.

Demand so outstrips supply, he said, that trades rarely close because “no one's selling”.

The squeeze has produced strange behaviour. Some buyers have reportedly offered to swap their homes for Anthropic stock. It is the clearest sign yet that demand has run far ahead of anything on offer.

The SPV problem

Most trades that do happen route through special-purpose vehicles, which pool money from several buyers into one deal. Anthropic wants no part of them. Its own website warns investors to assume that any indirect route into its stock is invalid, and it has grown louder about scams.

The warning has not cooled anything. Buyers keep piling into the SPVs the company openly rejects, often paying steep fees to do it. Anthropic is riding a market it neither controls nor can police, which is awkward for anyone trying to price the stock before it lists.

What $1.2 trillion actually buys

Not much certainty. Secondary prices reflect illiquid, minority stakes with no board seats and no guaranteed exit. Even an early backer is wary. Matt Murphy of Menlo Ventures, one of Anthropic's first investors, calls secondary valuations a “noisy signal”, though he concedes the company's revenue has run “crazy above” its own plan.

The rivalry adds noise of its own. Interest in OpenAI has revived since it shipped its GPT-5.6 models, led by a flagship called Sol. Even so, brokers still see roughly five buyers chasing Anthropic shares for every two after OpenAI. Elon Musk's xAI, meanwhile, closed a $20bn round before being folded into SpaceX.

Why it matters

Anthropic filed confidentially for an IPO in June, with a listing expected within months. That is when the scarcity vanishes. A public market floods the system with shares, and the $1.2 trillion figure finally meets buyers who can walk away. Private froth has minted eye-watering numbers before, from SpaceX's contested valuations to OpenAI's own trillion-dollar wait.

The question for Anthropic is whether a price set by a handful of desperate buyers survives contact with everyone else. Its fast-growing Claude business will have to do the arguing.