Mizuho Securities conducted an experiment asking AI agents how to deploy spare cash, and the results largely bypassed Circle's USDC stablecoin. The bank now models a potential $4 billion to $9 billion reduction in USDC's market value based on these findings. The test highlights growing concerns about whether major stablecoins will be integrated into AI-driven financial workflows, with USDC appearing notably absent from most AI agent recommendations for idle fund allocation.