Agentic Commerce Protocol (ACP)

The Agentic Commerce Protocol is an open standard, co-developed by OpenAI and Stripe and announced 2025-09-29, that lets an AI agent (initially ChatGPT) complete a purchase on a shopper's behalf — branded "Instant Checkout." It is the specific protocol underneath the broader Agentic Commerce movement, and competes with Google's Google Agent Payments Protocol (AP2) and the Shopify/Google Universal Commerce Protocol (UCP). As of mid-2026 the infrastructure is live but the commercial model is under visible stress — OpenAI pulled back native in-chat checkout in March 2026.

What it is and who controls it

ACP is described in its own repo as an interaction model and open standard connecting buyers, their AI agents, and businesses to complete purchases; it is currently in beta (ACP GitHub README). OpenAI's launch post cited 700M+ weekly ChatGPT users, with Etsy live first and "over a million Shopify merchants" planned (OpenAI, 2025-09-29).

Governance is Apache 2.0, "jointly governed by OpenAI and Stripe as Founding Maintainers, with a clear path toward broader community governance" and a stated "Future Path: Neutral foundation stewardship as ecosystem matures." Decisions are "consensus-based with escalation procedures"; contributors sign a CLA; major changes route through a "SEP" proposal process (ACP GitHub README).

How it works

The merchant remains the merchant of record; ChatGPT acts only as the user's agent, passing information between user and merchant, while the merchant accepts/declines the order, processes payment via its existing provider, and handles fulfillment, returns and support (OpenAI, 2025-09-29). This is the key design choice — the platform positions itself as a "digital personal shopper," not as the seller.

The spec exposes building blocks including an Agentic Checkout API, a Delegate Payment spec, and (from the 2026-04-17 snapshot) cart, product feed, orders, and delegated authentication, with OpenAPI and JSON Schema definitions (ACP GitHub README).

Spec timeline (as-of 2026-06-26)

Snapshot	Added
2025-09-29	Initial release
2025-12-12	Fulfillment
2026-01-16	Capability negotiation
2026-01-30	Extensions, discounts, payment handlers
2026-04-17	Cart, feed, orders, authentication, MCP

Payments: the Shared Payment Token

ACP's payment layer is delegated. A Stripe merchant can enable agentic payments "in as little as one line of code"; non-Stripe merchants participate via Stripe's Shared Payment Token (SPT) API or by adopting ACP's Delegated Payments Spec without changing their processor (OpenAI, 2025-09-29).

A Shared Payment Token (SPT) is a scoped grant: the agent gives a seller one-time use of the customer's payment method, with usage limits (currency, max amount, expiration). When the seller confirms a PaymentIntent with an SPT, Stripe clones a new PaymentMethod from the customer's original credential, so the seller never touches the underlying card data; the agent can revoke at any time; webhooks fire on use, revocation, or expiry (Stripe Docs).

SPTs currently support cards, Link, Apple Pay, Google Pay, Klarna, and (limited) Affirm, and are US-only for agents, customers and sellers (Stripe Docs, as-of 2026-06-26). Stripe notes the SPT layer can sit on top of card-network agent schemes — provisioning tokens via Mastercard Agent Pay and Visa Intelligent Commerce on the seller's behalf (Stripe Docs).

ACP vs the alternatives

[!unverified] Secondary explainers report AP2 launched ~2025-09-16 with 60+ partners (Mastercard, PayPal, Coinbase, Amex, Salesforce) across fiat + stablecoin rails, and that Visa integrated its network into ChatGPT ~2026-06-10 with user-set spending limits. Not confirmed against primary Google/Visa sources.

The March 2026 pivot

The most significant development for this protocol is a retreat. Per Forrester (2026-03-07), OpenAI scaled back native Instant Checkout in early March 2026, moving checkout into merchants' own apps-within-ChatGPT or back to merchant websites — repositioning the answer engine as a referral channel rather than the point of sale.

What practitioners / analysts report

• Only ~12–30 Shopify merchants were ever live, a tiny fraction of Shopify's millions; Shopify's ChatGPT-specific landing page now redirects to its homepage (Forrester, 2026-03-07).
• In-chatbot conversion ran ~3× lower than click-through to the merchant's own site (Walmart); Etsy said the feature hadn't delivered meaningful sales volume, working mainly as discovery (CNBC, 2026-03-24, via search summary).
• Forrester's Dec 2025 survey: 23% Gen X / 32% Millennial / 35% Gen Z US online adults used ChatGPT to search for products in the past month, but completing a purchase inside an answer engine was the least-adopted use case (Forrester, 2026-03-07).
• Forrester: inventory management was "disastrously absent" — feeds surfaced out-of-stock or unintended items — and advises merchants to retain the checkout moment (data + margin). (Note: analyst opinion, attributed.)

Key terms

Term	Meaning
Instant Checkout	OpenAI's ChatGPT buy-in-chat feature, powered by ACP
Merchant of record	The party legally selling — under ACP this stays the merchant, not OpenAI
Shared Payment Token (SPT)	Stripe's scoped, revocable grant of a payment method to a seller for one agentic purchase
Delegated Payments Spec	ACP's processor-agnostic path for non-Stripe merchants
SEP	ACP's structured proposal process for spec changes
Mandate	AP2's signed Verifiable Credential (Intent / Cart / Payment) — the competing model

Open questions / frontier

• Exact ACP merchant fee (OpenAI: "a small fee"; secondary "4%" unconfirmed).
• Whether ACP, Google Agent Payments Protocol (AP2), or Universal Commerce Protocol (UCP) consolidates the market, or they coexist.
• No primary ACP GMV / transaction-volume figures exist publicly yet.