Anthropic study finds analysts followed Claude Code's arbitrary lean 86% of the time

Anthropic researchers ran a randomized controlled trial in which 50 professional analysts used Claude Code (Claude Opus 4.8) to advise a fictional farming cooperative, with the agent secretly assigned a coin-flip lean on four analytical choices. Analysts matched their agent's lean 86% of the time, switched away from their own prior preference 60% of the time when the agent disagreed, and 77% later repeated the agent's arguments while only 15% credited the agent. The authors caution that the leans were deliberately strengthened and the study covered one task and one model, but note the results raise concerns about whether human sign-off remains an independent check as agents take on more research work.