AI Agents in DeFi: Why Automated Wallets Could Increase Smart Contract Risk

AI agents that hold keys and submit transactions are moving from experiments to active on-chain participants, raising new operational and systemic risks for DeFi. Recent incidents — a May 4 prompt‑injection drain of 3,000,000,000 DRB (~$150k–$180k) and a mid‑May Bankr outage affecting 14 wallets (~$440k linked addresses, some losses ~ $150k each) — show autonomous wallets can execute valid but malicious transaction chains without protocol exploits. Keyrock/partners report ~176M agent transactions (~$73M settled, ~98.6% in USDC) from May 2025–Apr 2026, highlighting scale. The piece argues this will force product and audit changes (short‑lived session keys, granular approvals, allowlists, policy audits) and increases counterparty and smart‑contract risk for DeFi users and builders, potentially slowing naive agent adoption until guardrails improve.