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Circle announced support for Proof’s x401 open protocol on 2026-06-26, arguing…

2026-06-26 · 15:42 UTC ·@circle ·0 min read

Brief

Circle highlighted Proof’s June 26, 2026 launch of x401, an open protocol that verifies who authorized an AI agent’s actions, positioning it alongside x402 (which covers agent payment). Proof built x401 with payments, identity, and AI contributors and published live demos and a CLI so services can request authorization proof today.

Why it matters

Circle announced support for Proof’s x401 open protocol on 2026-06-26, arguing the agentic economy needs open standards for both payment and identity.

Key details

  • Proof’s x401 verifies who authorized an AI agent’s actions; it complements x402 (which addresses how an agent pays) and ships with live demos and a CLI available immediately.
  • The x401 specification was developed by Proof with contributors across payments, identity, and AI to let any online service request proof of authorization for agent actions.
Source evidence

The agentic economy needs open standards for both payment and identity.

Circle is proud to support @proof's launch of x401, an open protocol for verified identity in the agentic economy.

x402 answers how an agent pays. x401 answers who authorized the action.

proof.com/blog/identity-infr…

Link

Proof Launches x401, the Open Protocol for Verifying the Authority Behind AI Agents

Developed by Proof with contributors across payments, identity and AI, x401 lets any online service request proof of who authorized an agent’s actions. Live demos and a CLI are available today.
proof.com