AI Agent Identity Gets x401 Protocol From Proof

Proof has launched x401, an open protocol that lets any website ask an AI agent to prove who it is acting for and what that person authorized. According to the company's announcement distributed via GlobeNewswire on October 15, 2026, the launch marks the first production deployment of verified legal identity and transaction authorization for the agentic web — production-grade AI Agent Identity delivered as open infrastructure.

At the center of the launch is an agent identity wallet held by the consumer. The wallet stores a verified legal identity and lets the person approve, on their own device, exactly what their AI agent may do. The agent carries the request; the person's wallet signs it. The business receiving the request can independently confirm the consumer's verified legal identity and check the cryptographic signature on the transaction itself. If the agent alters the amount, the recipient, or any other signed terms, the signature no longer validates.

Proof is an identity infrastructure company that operates a WebTrust-audited certificate authority and PKI-anchored digital credentials. According to the announcement, more than $1 trillion in transactions have been secured on its platform, and its network spans over 8,000 businesses across mortgage, automotive, wealth, insurance, and enterprise markets. The company created the online notarization category and operates the Notarize Network.

Access Is Not Authority: The Agent Evidentiary Gap

The launch arrives weeks after a high-profile confrontation exposed the problem x401 is designed to solve. On September 8, Meta released Muse, an AI agent capable of completing purchases; it reached No. 1 on the U.S. App Store, and Shopify connected Shop Pay. On September 21, Amazon blocked Muse, citing concerns that the agent did not identify itself, appeared to collect customer credentials, and moved through accounts and transactions without Amazon's knowledge or consent.

Proof calls the underlying issue the Agent Evidentiary Gap: the distance between what an AI agent can technically do and what a business can verify the person behind it authorized. An agent may possess a valid password, an OAuth token, an API key, or a payment card. None of those establishes that the person behind it authorized a particular action.

For merchants, that gap creates fraud and dispute risk. For banks, lenders, and insurers, it raises questions about legal identity, consent, and enforceability. The industry's response is accelerating on both sides of the trust problem: while Proof tackles authorization, established players are investing in AI security, as seen in Cohere's acquisition of AISLE in an AI cybersecurity deal. Consumers are wary as well. In a survey of 1,000 U.S. consumers conducted by Exploding Topics and cited in the announcement, 31 percent said they would not let an AI agent spend any money on its own. More than half, 51 percent, said they were uncomfortable with AI tools storing their card details.

Regulators have begun clearing a path. In September, FinCEN, together with staff from the Federal Reserve, the FDIC, the NCUA, and the OCC, updated Customer Identification Program guidance to expressly recognize digital certificates and verifiable credentials, including those issued by nongovernment third parties, as permissible methods of customer identity verification, provided the institution ensures the issuer applies the same level of authentication the institution itself would use.

How x401 Works: Verify the Person, Sign the Action

The x401 protocol extends HTTP 401, the web's standard unauthorized-response mechanism, allowing a website to specify the evidence an AI agent must provide before proceeding — establishing AI Agent Identity as verifiable evidence rather than an unverified claim. A website can request verified identity claims, such as legal name, age, or nationality, from trusted issuers at a required level of assurance. It can also request that the consumer cryptographically sign the terms of a specific transaction.

Three capabilities are live at launch. First, Proof's agent identity wallet, which shows the information and transaction terms being requested. Second, x401 itself, the open HTTP protocol for requesting and verifying that evidence. Third, a production Model Context Protocol server that works with Meta's Muse, ChatGPT dots, Grok, Claude, and other assistants that support MCP.

The flow puts the human at the decision point. The agent presents the website's request to the consumer, who authenticates with a biometric on their own device. The wallet displays the information and transaction terms being requested. When the consumer approves, a hardware-protected key signs the presentation, binding verified legal identity to the specific terms authorized. The website then verifies the issuer, the credential, the signature, and the transaction terms before proceeding. It can retain the signed evidence and independently validate it later if the transaction is disputed.

The distinction is consequential: the protocol does not merely establish who someone is. It creates verifiable evidence of exactly what that person agreed to. Consider an AI agent instructed to transfer $25,000 from a consumer's bank account. The bank can issue an x401 challenge requiring both verified legal identity and a signature on the wire instructions, including the amount, the recipient, and the source account. The consumer reviews and approves those details on their own device, and the bank verifies the signed instructions alongside its own existing requirements before executing the transfer. If any signed detail changes, the evidence fails verification.

Proof supports transaction signing for wire instructions, payment mandates, itemized purchases, and developer-defined transaction data, so the same infrastructure can protect financial transactions, contracts, account changes, and other high-consequence actions. Websites can request verified identity claims without a sales process or a negotiated agreement, and developers can deploy through a reference implementation for Cloudflare Workers, with guides for Node, Python, Go, and other environments.

x401 Meets x402: Identity, Authorization, and Payment

As AI agents increasingly transact across the internet, businesses need to establish three things: who is behind the agent, what that person authorized, and how the transaction gets paid. Proof designed x401 to work alongside x402, the HTTP-native payment protocol now stewarded by the Linux Foundation, which had more than 40 member organizations as of July 2026, including Visa, Mastercard, Stripe, Google, AWS, Circle, and Coinbase.

According to the announcement, x401 establishes who is behind a request and can carry cryptographically signed evidence of what that person approved, while x402 enables the payment. Together, the protocols give developers a way to combine verified legal identity, signed transaction authorization, and payment without requiring either protocol to replace the other. The launch is part of a broader wave of enterprise agent infrastructure investment, including Labelbox's $100M+ Series E for reinforcement learning and managed agents.

Proof is also using x402 to change the economics of identity verification itself. Historically, identity providers relied on enterprise agreements and billing relationships, because collecting payment for a single verification costing cents was impractical. With x402, a website can pay per claim, with no purchase order, invoice, or minimum commitment. Identity can now be metered like bandwidth or compute: one API request, one agent purchase, or one machine-signed document at a time.

Early adopters are already putting it into production. Superfluid, which operates infrastructure for continuous settlement of tokenized markets, announced the first live implementation of x401 as part of the Superfluid Wallet launch in September. According to ID Tech Wire's reporting on the integration, the wallet connects agent-initiated transactions to a verified individual or business while keeping the human owner in control, with agents proposing actions and people approving them under defined policies. Superfluid's founder and CEO, ZhiCheng Miao, said in the announcement that portable, verifiable identities give the services an agent interacts with a way to verify who that agent represents, and that agents acting for people while people stay verifiably in charge is the foundation agentic commerce needs.

A Trust Layer With Legal Footing

U.S. law has recognized transactions formed by electronic agents for more than 25 years. Under the federal ESIGN Act and the Uniform Electronic Transactions Act, electronic-agent transactions can have legal effect when the agent's actions are legally attributable to the person to be bound. As Proof uses the term, a verified legal identity is a person's identity established from government-issued identity evidence through NIST IAL2 identity proofing, bound to a certificate issued to that person. Each verified person holds an X.509 certificate issued by Proof's WebTrust-audited certificate authority following Kantara-certified NIST IAL2 identity proofing, bound to a hardware-protected key. The credential belongs to the person, not an institution, and can be reused across relationships. Selective disclosure allows consumers to share specific identity attributes without exposing their entire identity document.

Interoperability is part of the design. The protocol is built to work with AP2 and Verifiable Intent, the specifications developed by Google and Mastercard and now stewarded by the FIDO Alliance, for recording what a person authorized an agent to do. According to BitRss's coverage of the launch, Proof plans to submit x401 to the FIDO Alliance's agentic authentication standards workgroup for adoption.

The company first published x401 in June 2026 with technical contributors from payments, identity, and AI organizations, including Visa, Circle, and Okta, and it intends to place the protocol under neutral, independent governance. The specifications cover credential formats, issuance, custody, presentation, transaction signing, agent delegation, settlement, claims, offline verification, and implementation guides, providing what independent implementations, audits, and competing credential issuers need to build on it.

Proof's founder and chief executive, Pat Kinsel, said the agentic web needs a trust layer backed by evidence, and that businesses are being asked to accept instructions from software acting for a customer without being able to prove who that customer is or what was approved. Blocking agents, he said, is understandable but not sustainable, and the company is making verified legal identity and authorization available as open web infrastructure to anyone, without a sales call. As the launch announcement puts it, as AI agents take on increasingly consequential tasks, businesses will need more than a valid login or a successful payment. They will need verifiable evidence of the person behind the transaction, and of what that person authorized.

Proof will demonstrate the end-to-end experience at Money20/20 in Las Vegas from October 18 to 21, and will host developer sessions for organizations implementing the protocol. The protocol, identity scheme, implementation guides, and reference implementation are available to developers now, and ID Tech Wire's earlier reporting on the Superfluid integration shows production deployments are already underway.