Anthropic ran an internal marketplace experiment (published April 24) where 69 employees had Claude agents buy and sell personal belongings via Slack — without human intervention. Opus-powered agents completed roughly two additional deals per user and extracted ~$2.68 more per item sold compared to weaker Haiku agents, yet participants using Haiku reported identical satisfaction and fairness scores — a result Anthropic calls a "perception gap." The experiment completed 186 deals totaling over $4,000; prompting agents to negotiate aggressively produced no statistically significant improvement either way.