Countersign: ENS-Native Identity and Verifiable Spending Authorization for Autonomous AI Agents

COUNTERSIGN lets an autonomous agent propose payments without being able to change the recipient or amount after a human approves them. It uses typed payment intents, an on-chain spending-policy contract, and a transaction-specific owner signature combined with a fresh-authentication attestation. Settlement uses official test USDT on Whitechain Sepolia. ENSv2 provides a separate identity and policy-discovery namespace, and a World sandbox OpenID Connect flow provides authentication evidence. The paper describes the protocol, its replay domains, its cancellation and revocation boundaries, and a reproducible test artifact: 157 Node tests and 131 Solidity test executions. This is an implementation case study, not a claim to have invented transaction-bound authorization. It is not independently audited, and it makes no claim of production identity assurance.