Anthropic’s Project Swap tested Claude agents trading books for people

Anthropic has reported results from Project Swap, a book-trading experiment designed to examine how Claude agents behave in a marketplace on people’s behalf. The project was described as a more controlled follow-up to Project Deal, Anthropic’s earlier marketplace experiment. Anthropic dated its report Sep 24, 2026. The barter market included 201 Anthropic employees and their Claude-powered agents.

Employees across six offices contributed books to give away, then chatted with Claude about what they hoped to read. Each agent entered a digital trading floor to propose exchanges and negotiate with other agents. To assess how well agents captured participants’ preferences, the researchers also had participants rank 10 books. After a five-minute conversation, an agent’s ranking matched its participant’s ranking for 61% of book pairs.

Anthropic said the agents negotiated effectively, while the market’s main weakness was that they did not know enough about the people they represented. The company replayed each trading floor dozens of times with different models and agent instructions. In those trials, the model used by an agent affected negotiation results more than the instructions did. Markets using stronger models were more efficient, according to the report.

Most participants who read their acquired book liked it, and the average participant said they would let Claude spend about a third of their annual book budget. Anthropic presents the experiment as an early test of issues that could matter as agents take part in real markets. It says agent builders need ways to check whether systems understand the people they represent. Market designers, meanwhile, need to decide who can participate, what happens if a deal fails, and how much activity participants can see. Those findings put preference gathering and clear marketplace rules alongside negotiation ability as design questions for builders.