From ChatGPT discovery to merchant checkout

The situation

A shopper asks ChatGPT for a pair of trail running shoes, finds a pair from a retailer, and buys them. The shopper is present throughout. The retailer is the merchant of record, and its name appears on the card statement.^{Source [1]}

What ChatGPT does in this journey changed in 2026. On 2026-03-24 OpenAI expanded ACP to product discovery and let merchants use their own checkout while it focused on discovery.^{Source [2]} Today two checkout paths exist for ChatGPT apps, and they differ in status. External checkout on the merchant’s site is the recommended path and is generally available.^{Source [3]} Checkout inside the ChatGPT payment sheet is a private beta for select marketplace partners.^{Source [3]} The ACP specification itself is labeled beta, and its core RFCs are Drafts.^{Source [4, 5, 6]}

Actors

• Shopper, who asks, picks and confirms.
• ChatGPT, the agent surface that shows products and, in the beta, the payment sheet.
• Merchant’s ChatGPT app, an MCP server with a widget, built on OpenAI’s Apps SDK rather than on ACP.^{Source [3, 7]}
• Merchant, which owns the catalog, the website checkout and, for Level 1 merchants, a card vault.
• Feed provider, optional: OpenAI names Salesforce and Stripe as providers that can deliver merchant feeds.^{Source [2]}
• Merchant PSP, which charges the payment.

Step by step

1. Push the feed (ACP). In ACP the Feed API is hosted by the agent and called by the merchant.^{Source [8, 9]} A Product needs id and variants, and each Variant needs id and title.^{Source [10]} OpenAI’s own API uses /product_feeds paths and adds promotions.^{Source [1]} OpenAI recommends a full daily file plus API updates during the day.^{Source [1]} Onboarding is limited to approved partners.^{Source [1]}
2. Ask (no protocol). The shopper describes the shoes.
3. Discover (ACP). ChatGPT shows products from merchant feeds. OpenAI named Target, Sephora, Nordstrom, Lowe’s, Best Buy, The Home Depot and Wayfair as integrated for discovery.^{Source [2]} Shopify data arrives through Shopify Catalog, and buyers complete purchases on the merchant’s store.^{Source [2]}
4. Open the app (Apps SDK). ChatGPT calls the merchant’s MCP server and the widget shows the offer.
5. Path A: link out. The app sends the shopper to the merchant’s checkout.^{Source [3]}
6. Path A: pay on the site (no protocol). The merchant’s normal web checkout runs.
7. Path A: authorize (card rails). The merchant’s PSP authorizes as for any web order. Path A ends here.
8. Path B: open the sheet (Apps SDK, beta). The widget calls requestCheckout.^{Source [3]}
9. Path B: confirm. The shopper picks a saved payment method and buys.
10. Path B, Level 1 merchants only: Delegate Payment (ACP). A merchant with a PCI DSS Level 1 certificate can receive raw card data by implementing the ACP Delegate Payment endpoint, including allowance constraints.^{Source [3]} The request requires payment_method, allowance, risk_signals and metadata.^{Source [11]} The allowance requires reason, max_amount, currency, checkout_session_id, merchant_id and expires_at, and the only reason is one_time.^{Source [11]}
11. Path B, Level 1: vault token (ACP). The response is HTTP 201 with an id starting vt_.^{Source [11, 12]}
12. Path B: tool call (Apps SDK). ChatGPT sends a token for the selected payment method to the merchant’s MCP server in a complete_checkout tool call.^{Source [3]} No source read says this token is an allowance-scoped delegated token in the general case.^{Source [3]? unverified}
13. Path B: charge. OpenAI lists Adyen, Checkout.com, Fiserv, PayPal, Stripe and Worldpay as supporting payment sheet processing.^{Source [3]}

Which protocol does what

The latest released ACP version is 2026-04-17.^{Source [8, 13]} The Apps SDK complete_checkout tool is not the ACP MCP binding’s complete_checkout_session.^{Source [3, 7]}

Where controls apply

• Before authorization. OpenAI excludes categories such as alcohol, weapons and prescription-only medications from ChatGPT shopping.^{Source [1]} ACP carries no signed proof of user intent beyond scoped tokens and the agent’s own confirmation UI.^{Source [6, 14]} In path A the merchant’s own checkout holds consent, fraud screening and 3DS.
• At signing. On the Delegate Payment path the allowance caps the amount and binds the token to one merchant and one checkout session.^{Source [11]} OpenAI may require a PCI attestation of compliance before enabling production Delegate Payment.^{Source [1]}
• At the edge. ACP pairs authenticate with bilateral bearer tokens, and the specification has no agent registry or public key directory.^{Source [5, 15]} OpenAI asks merchants to allowlist its published egress IP ranges.^{Source [1]}
• At settlement. The merchant’s PSP charges the payment and enforces the allowance when there is one. ACP defines no token status field and no error code for a token used outside its allowance.^{Source [11, 12]}
• After the fact. The merchant handles refunds and chargebacks as merchant of record.^{Source [1]} ACP has no revocation endpoint.^{Source [6, 16]}

What is observable from outside

Very little. A seller’s discovery document at /.well-known/acp.json needs no authentication.^{Source [17]} There is no public explorer, indexer or registry of ACP merchants.^{Source [18]} Feeds, tool calls, tokens and allowances all travel point to point.^{Source [3]} No official ACP transaction volume, GMV or merchant count has been published.^{Source [2, 4, 14]? unverified} Outsiders learn about adoption from announcements, such as OpenAI’s list of discovery retailers.^{Source [2]}

What can go wrong

• Stale or partial feed. ACP file ingestion replaces the whole product set, so a partial file drops products.^{Source [8]} The shopper sees a wrong price or a missing item until the next feed.
• Card data in the wrong place. OpenAI’s docs say the feed and checkout specs carry no cardholder data, while direct Delegate Payment handles it and is likely in PCI scope.^{Source [1]} Implementations must not log full card numbers or CVC values.^{Source [5, 12]}
• Delegate Payment errors. The endpoint returns codes such as invalid_card, duplicate_request and idempotency_conflict.^{Source [11]}
• Who bears the loss. The merchant is merchant of record and carries refunds and chargebacks.^{Source [1]}
• Costs. ACP charges no protocol fee; merchants pay their own PSP.^{Source [1, 19]} OpenAI has not published a fee rate for ChatGPT checkout.^{Source [2, 14]? unverified} A report said Shopify merchants would pay OpenAI 4% on ChatGPT checkout sales (reported).^{Source [20]}

Variants

• History: Instant Checkout in its 2025 form. OpenAI announced Instant Checkout with ACP on 2025-09-29.^{Source [14]} At launch it supported single-item purchases from US Etsy sellers.^{Source [14]} Stripe introduced the Shared Payment Token the same day, the first Delegated Payment Spec-compatible implementation.^{Source [1, 21]} That flagship form was scaled back in March 2026.^{Source [2, 22]} Trade press reported an OpenAI spokesperson saying Instant Checkout was moving to apps (reported).^{Source [22]} Do not read it as today’s default path.
• A full ACP checkout session. An agent can also run ACP’s own checkout: POST /checkout_sessions creates a session and complete must return completed with an order.^{Source [5, 23]} That is the protocol as specified; this scenario follows what ChatGPT documents today.

# Illustrative example, ACP spec version 2026-04-17. OpenAI's production API uses /product_feeds paths.
PATCH /feeds/feed_us/products HTTP/1.1
Content-Type: application/json

{
  "products": [
    {
      "id": "prod_1",
      "title": "Trail running shoe",
      "variants": [ { "id": "prod_1_m10", "title": "Men's 10" } ]
    }
  ]
}