On September 24, 2026, Anthropic published Project Swap. 201 Anthropic employees told Claude what books they liked, and Claude ranked the books on offer for them. Agents traded books on a shared floor. Between 78% and 96% of agents, depending on the model, named the book at the top of that ranking at some point, and only about 1 in 100 of those lied. Only 10% of agents went further and said where three or more books ranked, on the 80 floors where none was told to be ruthless or prosocial. Anthropic’s published prompt told agents to feel free to say anything and says nothing about sharing the ranking.
Why It Matters
Anthropic’s reasoning is that naming your top pick tells whoever holds it you can be made to wait, so they may as well hold out for more. The study didn’t measure what that cost anyone, and it was a book swap with no money at stake. But an agent that negotiates decides, message by message, what the party across the table learns. A purchasing agent that mentions your deadline, your budget ceiling or that no other supplier has quoted would be making the same kind of choice.
The Decision
The question is what your agent may say about what you want. Letting it state priorities gives that party something to work with, and Anthropic notes a seller can’t sell if the buyer reveals nothing. Holding it back may protect your position and can cost you deals.
What To Do This Week
- Ask the owner of one agent that deals with outsiders to list what it knows about your side that a counterparty would want.
- Ask IT to pull that agent’s last ten outside messages and mark any that state something on the list.
- For each mark, ask your COO if the company would have said it. Add the answers to the agent’s instructions as what it may say and what it may not, then read its next ten messages. Anthropic didn’t test whether such a rule holds.
What Not To Do
Don’t assume “negotiate hard” means “say little.” On floors where Anthropic told half the agents to be ruthless and half prosocial, the instruction made no difference to how often they named their top pick. Neither instruction mentioned disclosure. Read what your agent says before you clamp down.
Signal Boost
Project Swap: What happens when agents trade for us?, Anthropic, September 24, 2026. Its section on what agents said on the trading floor holds the top-pick figures.