Proof launched x401 on Thursday, an open protocol that lets any website ask an AI agent to prove who it is acting for and what that person approved. The company says it is the first to put verified legal identity and transaction authorization for AI agents into production.

At the centre is an agent identity wallet holding a person's verified legal identity. The person approves exactly what an agent may do on their own device; the agent carries the request and the wallet signs it, so if the agent changes an amount, recipient or other signed term, the signature no longer validates. The wallet, the x401 protocol and verification tooling are live today.

Proof says it works with assistants that support the Model Context Protocol, naming Meta's Muse, ChatGPT dots, Grok and Claude. The launch follows Amazon blocking Muse from its marketplace and September guidance from FinCEN and federal banking regulators recognising verifiable credentials as a permissible way to verify customer identity.