Protocols

Revives the dormant HTTP 402 status code: a server answers a request with 402 and machine-readable payment requirements, the agent signs and pays in stablecoin, a facilitator verifies and settles on-chain, and the request is retried with a payment header. Governance transferred to the vendor-neutral x402 Foundation under the Linux Foundation in 2026, with 40 founding members including Visa, Mastercard, Stripe, Adyen, and AWS.

An open interoperability layer for agent-to-agent communication: it lets independent agents discover each other, exchange capabilities, and coordinate tasks. It is not a payment-execution protocol itself — payments ride on top via other protocols.

An authorization and governance framework for agent-initiated payments. It defines verifiable mandates that capture user intent and constraints, so an agent can transact on a user's behalf with an auditable chain of consent. Complements A2A and is rail-agnostic. Google donated AP2 to the FIDO Alliance in April 2026; v0.2 added Human-Not-Present autonomous transaction flows.

An open, internet-native protocol for machine and agent payments, co-authored by Stripe and Tempo. Spans both card (via Shared Payment Tokens) and stablecoin rails, settling through Stripe's existing infrastructure. The spec is open at mpp.dev; Stripe acceptance is in early access as of September 2026.

An account-abstraction standard that enables programmable smart-contract wallets on Ethereum without consensus-layer changes. It is a supporting custody primitive for agent payments — session keys, spending limits, gas abstraction — not a payment protocol in its own right.

India's first agentic payment protocol on UPI. Extends UPI's mandate framework so an AI agent can complete a payment after a single upfront user authorization, with no per-transaction human authentication. Combines UPI mandate rails, an HTTP 402 discovery layer, and the Grantex identity/audit layer.

A cryptographic trust framework for agentic commerce on the Visa network. Uses RFC 9421 HTTP Message Signatures so a Visa-approved AI agent can prove its identity, consumer authorization, and payment credentials to merchants — letting merchants distinguish legitimate buying agents from bots. Live in Europe with 30+ issuers since July 2026.

A Mastercard network service for high-frequency, low-latency machine-to-machine payments. Builds on the Agent Pay program (2025) with credentialing via Verifiable Intent, programmable permissioning, and multi-rail settlement. Launched June 2026 with 30+ partners including Stripe, Adyen, Coinbase, and Cloudflare.

A research-stage payment architecture (arXiv, Mar 2026) that binds crypto payments to verifiable service execution for machine-to-machine commerce. It is positioned explicitly as addressing x402's lack of end-to-end atomicity across execution, payment, and delivery.

An open-source payment protocol from Ant International for mobile interfaces — digital wallets, super apps, smart devices, and wearables — enabling AI agents to execute payments through existing mobile payment rails. Launched April 2026; global rollout across the Alipay+ ecosystem (10 wallets, 7 acquirers) announced September 2026. Ant International, Mastercard, and Visa are collaborating on a Know-Your-Agent (KYA) interoperability framework through BuildFin.ai (MAS).