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). By mid-2026, the protocol has pivoted from a consumer checkout product to backend infrastructure: OpenAI's Instant Checkout was quietly shut down in March 2026 after ~five months of near-zero sales, and the current model is discovery-in-AI, checkout-on-merchant-site (as-of 2026-08-31).

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, as-of 2026-09-03). 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).

Who authored ACP. Official repo: "maintained by OpenAI and Stripe." VS a search result claiming "Stripe, OpenAI, and Meta." Meta is not named in the repo — treated as unverified and excluded.

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 2026-09-03)

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
Post-2026-04-17	No new stable release; `unreleased/` directory active (51 open PRs, 85 open issues) (as-of 2026-09-03)

Merchant fee

ACP merchant fee. eMarketer (Jan 23, 2026) confirmed OpenAI charged Shopify merchants 4% per Instant Checkout sale in addition to Stripe's standard ~~2.9%+$0.30 (~~$7.20 combined on a $100 order); merchants had to opt in explicitly. eMarketer also noted "Neither Google nor Microsoft is currently charging Shopify merchants additional fees for purchases made through their chatbots" (as-of 2026-01-23). Digital Applied (June 2026) notes the fee's "present applicability [on ChatGPT Apps, post-Instant-Checkout shutdown] is unconfirmed." No primary OpenAI press release directly stating "4%" was found — the figure comes from eMarketer reporting, which is near-primary.

The 4% fee is widely cited in industry analysis as a primary factor in merchant rejection of Instant Checkout and in the platform's loss of early momentum to Universal Commerce Protocol (UCP) (Digital Applied, June 20, 2026; eMarketer, Jan 23, 2026).

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).

SPT payment methods (as-of 2026-03-03)

Cards, Link, Apple Pay, Google Pay, Klarna, Affirm; plus Mastercard Agent Pay and Visa Intelligent Commerce (agentic network tokens), added March 2026 (Stripe blog, 2026-03-03). Stripe described itself as "the first and only provider that supports both agentic network tokens and BNPL tokens in agentic commerce through a single primitive" (as-of 2026-03-03).

SPT July 2026 update (as-of 2026-07-29)

Stripe changelog entry 2026-07-29 (API version 2026-07-29.preview, breaking change): adds redirect_to_url as a new next_action.type on SharedPaymentIssuedToken, alongside existing use_stripe_sdk. SPTs now support 3DS authentication via redirect flows — merchants not using Stripe SDK can supply a return_url instead. This is the first functional post-June-2026 change to the SPT API (Stripe Changelog, 2026-07-29).

SPT geographic status (as-of 2026-09-03)

SPT/Instant Checkout was US-only for agents, customers, and sellers. Instant Checkout was shut down in March 2026; no geographic expansion of the ChatGPT checkout channel has been announced. SPT as an API primitive carries no explicit geographic restriction in Stripe docs; the US-only constraint applied to the ChatGPT consumer surface (Stripe changelog, accessed 2026-09-03).

SPT early retail adopters

Etsy and URBN (Anthropologie, Free People, Urban Outfitters) confirmed as early SPT adopters (Stripe blog, March 3, 2026).

The March 2026 pivot: Instant Checkout failure

The most significant development for this protocol is the failure and retreat of its flagship consumer product. OpenAI quietly shut down native Instant Checkout in early March 2026. The product ran approximately five months.

What went wrong

Digital Applied (June 20, 2026):

ACP's consumer surface "ran roughly five months with near-zero sales before being shut down"
Root causes: no sales-tax collection mechanism, no real-time inventory sync, only ~12 Shopify merchants ever integrated (from eligible millions), consumers reverted to familiar checkout at payment entry
Instant Checkout "had disastrously poor inventory management — feeds surfaced out-of-stock or unintended items" (Forrester, 2026-03-07, via existing vault)

What practitioners / analysts reported (existing + updated)

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)
4% fee was cited as making ACP less attractive than Google/Microsoft's fee-free integrations (eMarketer, Jan 23, 2026)

Post-shutdown pivot (as-of 2026-08-31)

OpenAI's current merchant page states it is "moving away from a standalone Instant Checkout experience." Current model: four explicitly separated layers — product feed, organic discovery, advertising (OAI-AdsBot), and checkout handoff to merchant (universalcommerceprotocol.blog, Aug 31, 2026).

[!unverified] Per press reports (Glossy, Quartz), OpenAI relaunched limited in-chat buying for Shopify merchants post-March, with brands Glossier, SKIMS, Spanx, Vuori, and Etsy sellers — discovery is now a gating requirement (secondary-sourced via universalcommerceprotocol.blog, Aug 31, 2026). Not confirmed against primary OpenAI sources.

Post-shutdown: ACP as infrastructure (2026)

Despite Instant Checkout's failure as a consumer product, ACP continues as B2B infrastructure powering ChatGPT Apps for product discovery. Confirmed ChatGPT App partners using ACP for discovery (not checkout): Target, DoorDash, Instacart (universalcommerceprotocol.blog, Aug 31, 2026).

At Shoptalk Spring 2026 (~March 2026), Meta demonstrated a Facebook checkout flow built on ACP, and OpenAI described expanding ACP from checkout into full discovery (YouTube — Shoptalk 2026 recap, ~March 2026).

Shopify agentic stack (July 2026): Shopify Hydrogen headless storefronts became first-class Agentic Storefronts by default via Storefront MCP in July 2026 — discoverable and transactable by ChatGPT, Perplexity, and Microsoft Copilot with no special integration required. Connectors confirmed: Claude, ChatGPT, Perplexity, Manus, Replit, Vercel (Digital Commerce 360, Aug 6, 2026).

ACP vs the alternatives

Protocol scope / philosophy. ACP (OpenAI+Stripe) keeps the merchant as merchant of record and leans on Stripe's SPT for payment. VS Google Agent Payments Protocol (AP2), positioned as vendor-neutral and payment-method agnostic, built on three signed "Mandates" (Intent, Cart, Payment) as W3C Verifiable Credentials, Apache-2.0, release v0.2.0 on 2026-04-28 (Google AP2 GitHub). The two are competing governance models for the same problem; sources do not declare a winner. (as-of 2026-06-26)

AP2 developments post-June 2026

AP2 v0.2.0 (April 2026): added "Human Not Present" autonomous payment mandates — agents can purchase items (e.g. limited-release tickets) the moment they go on sale without user confirmation (Google blog, April 2026)
Governance donated to FIDO Alliance (Google blog, confirmed): makes AP2 an industry-wide neutral standard. Practitioners rate AP2 governance longevity highest: AP2 (FIDO) > UCP (open coalition) > ACP (OpenAI/Stripe-controlled) (Digital Applied, June 20, 2026)

UCP developments post-June 2026

Universal Cart announced at Google I/O 2026 (May 19, 2026): persistent cross-surface cart spanning Search, Gemini, YouTube, Gmail; AI price-drop monitoring, back-in-stock alerts; built on Google Wallet infrastructure; integrates UCP
UCP launch partners at I/O: Nike, Sephora, Target, Ulta Beauty, Walmart, Wayfair, Shopify merchants (Fenty, Steve Madden) (as-of 2026-05-19)
UCP self-serve since June 17, 2026 via Shopify Spring '26 Edition — no approval gate required (as-of 2026-06-17)
Klarna formally adopted UCP (eMarketer, Feb 3, 2026)
UCP 20+ endorsers at NRF (Jan 11, 2026): Adyen, Amex, Mastercard, Stripe, Visa, Walmart, Target, Macy's, Best Buy, Zalando
eMarketer framing: "Protocols serve as the toll roads for agentic infrastructure. Payment providers who harness the most partnerships with key merchant and/or financing platforms serve to scoop the majority of early agentic volume windfalls." (eMarketer, Feb 3, 2026)

[!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.

Practitioner stack guidance (as-of 2026-06-20)

Digital Applied (June 20, 2026): standards are designed to stack, not compete — recommended layer architecture:

UCP for discovery and cart
AP2 for trust and payment authentication
ACP for execution in specific ChatGPT surfaces

Adyen Agentic (June 16, 2026): multi-standard adapter supporting UCP/ACP/AP2/Meta simultaneously — US enterprise only at launch (as-of 2026-06-16).

AI commerce context: what the metrics show (2026)

These platform-level figures provide context for ACP's opportunity and the trust ceiling it faces:

Shopify: AI-referred traffic up ~8× YoY Q1 2026; AI-referred orders up ~13× YoY Q1 2026; AI-referred conversion beats organic SEO in 23 of 25 merchant categories (+56% average); AI-referred AOV +14% (Shopify enterprise blog, May 2026; as-of 2026-Q1)
Adobe: AI-referred conversion swung from −38% vs non-AI (March 2025) to +42% vs non-AI (March 2026) — an 80-point shift (Adobe 2026 Q2 AI Traffic Report; as-of 2026-03)
eMarketer forecast: US AI-platform retail ecommerce ~$20.6 billion in 2026 (~1.5% of US ecommerce) (eMarketer, Dec 2025; as-of 2025-12)
Consumer trust ceiling (Checkout.com / YouGov, June 2026): 65% of US consumers trust AI to compare prices; only 14% trust AI to place an order autonomously; 24% say they will never delegate purchases to AI (as-of 2026-06, secondary-sourced)
Only ~3% of transactions currently involve an AI agent; ~89% of merchants say they are actively preparing (as-of 2026-06)
69% of merchants experienced AI-enabled fraud in the past year; only 3% felt well-prepared (PYMNTS survey, 2026, secondary-sourced)

Key terms

Term	Meaning
Instant Checkout	OpenAI's ChatGPT buy-in-chat feature, powered by ACP — shut down March 2026
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
ChatGPT Apps	ACP's post-Instant-Checkout consumer surface: discovery-only, checkout on merchant site
Storefront MCP	Shopify's Model Context Protocol connector making Hydrogen storefronts natively agentic (July 2026)
Human Not Present	AP2 v0.2.0 feature enabling fully autonomous agent purchases without user confirmation

Open questions / frontier

Whether ACP, Google Agent Payments Protocol (AP2), or Universal Commerce Protocol (UCP) consolidates the market, or they coexist as a stack — practitioner consensus leans toward stacking rather than winner-takes-all (as-of 2026-06-20)
ACP's current merchant fee applicability on ChatGPT Apps (post-Instant-Checkout era) — unconfirmed (Digital Applied, June 2026)
No primary ACP GMV / transaction-volume figures exist publicly (as-of 2026-09-03)
What the 51 open PRs in spec/unreleased/ contain — next spec iteration direction unknown
Whether SPT geographic expansion (beyond US) will follow as Instant Checkout was US-only; SPT API itself has no stated geographic restriction (as-of 2026-09-03)
Agentic Sizing — how agents handle fashion/apparel fit decisions remains an open problem not addressed by any protocol