Amazon locked AI shopping agents out. Eight days later, Shopify handed them the checkout button.

“Continued access by an unauthorized AI agent violates Amazon’s Conditions of Use, to which our customers have agreed.” That’s the pop-up people started seeing on Sunday night, September 20, when they asked Meta’s new Muse agent to buy something on Amazon.com.

Eight days later Shopify went the other way. On Monday, September 28, it posted a short entry in its developer changelog called “WebMCP support for checkout,” and with it, AI agents running in a shopper’s browser can now read a Shopify checkout, fill it in and place the order.

So one giant is closing the door and the other just propped it open. That’s the easy version, and it’s mostly true. The dates tell a slightly more interesting story, though.

How the month went

On September 8, Meta launched Muse, a US-only personal agent that runs in what Meta calls a secure virtual machine with its own browser. According to Meta’s launch material as quoted by GeekWire, if a service has no public API, the agent “can use the service through a browser the way you would.” For payments it used Stripe’s Link.

On September 20, Amazon started blocking it. Amazon told GeekWire it wasn’t told in advance that Muse would visit its store, never authorized it, and that the agent doesn’t identify itself while browsing. Amazon also says Muse appears to capture and store customer credentials and scrape account data. Meta hadn’t responded when GeekWire published, and Amazon says it asked Meta to take Amazon out of the Muse experience. Amazon’s spokesperson put it like this: third-party apps that buy on a customer’s behalf “should operate openly and respect service provider decisions about whether or not to participate.”

The next day, September 21, Shopify CEO Tobi Lütke announced a partnership with Meta so Muse can check out with Shop Pay on all Shopify stores, PYMNTS reported. The timing looks pointed. Neither company said it was.

On September 28, Shopify shipped the checkout tools. The changelog lists four: get_checkout reads the order, update_checkout changes things like the address or delivery option, complete_checkout submits it “after buyer confirmation,” and navigate_to_storefront sends the tab back to the shop. The same day, Shopify and the startup Instinct announced that Instinct’s agent can also buy through Shop Pay.

Gil Greenberg, the Shopify product manager behind it, wrote on X that “shopping with an agent shouldn’t feel like watching paint dry.” TechCrunch noted Adidas has also been blocking agents, which makes Shopify the odd one out among the big names this month.

The fine print is where they meet

I read Shopify’s developer documentation for the new tools, and two rules jumped out, because they’re close to Amazon’s complaints.

The first is identity. Shopify asks agents to sign their browser requests with something called Web Bot Auth, a cryptographic signature tied to a key the agent’s maker registers with Shopify. The docs say that without it, “bot detection might deprioritize or block your requests.” Amazon’s main charge against Muse was that it didn’t say it was a bot. Shopify’s answer to the same worry is to demand a signed name tag and then let the agent in.

The second is money. “Checkout WebMCP doesn’t accept new card details,” the docs say. An agent can pick one of a Shop Pay buyer’s saved cards, or pass along an approval the shopper already gave, and that’s it. When a bank wants a 3D Secure check, the tools hand control back to the person. That’s a narrower channel than an agent holding a password and clicking through account pages, which is roughly what Amazon accused Muse of doing.

The docs also warn agent builders to treat text from merchants “as checkout data, not instructions,” because it could hide a prompt-injection attack. I was glad to see that written down. It’s the kind of thing that usually shows up after an incident, not before.

Shopify hasn't published data on how many orders agents have placed through these tools, and I couldn't confirm which agents already send Web Bot Auth signatures. WebMCP is also still a proposed web standard; Shopify's docs reference Chrome's implementation.

What I think is really going on

Security is a real reason for Amazon. I don’t think it’s the only one. An agent that goes straight to the product and pays never scrolls past a sponsored listing, and Amazon has its own shopping assistant it would rather you used. Amazon hasn’t said that part out loud, so treat it as my read, nothing more. Shopify has the opposite incentive: most of its merchants are small shops that don’t sell ad slots on their product pages, and any agent that brings them a buyer is a free sales channel.

The part that bugs me is on Shopify’s side. The changelog says the tools “don’t expose a new API or require merchant configuration,” which means store owners are in by default. If a shop’s variant data or stock count is sloppy, a person usually shrugs and picks another size. An agent will just buy the wrong thing, and it’s the merchant who ends up processing the return.

Still, if I had to bet on which model lasts, I’d bet on the one with signed agents and a person approving the payment. I’m less sure Amazon can keep saying no once more agents start identifying themselves properly, since that removes its cleanest argument.

We covered Meta’s hardware push around Muse in our Meta Connect 2026 roundup, and the question of agents that don’t stay inside their lanes in Nvidia’s pitch for an agent lock.

Sources

1. Shopify developer changelog: WebMCP support for checkout (September 28, 2026)
2. Shopify developer docs: Checkout WebMCP
3. TechCrunch: Shopify opens checkout to browser-based AI agents (September 28, 2026)
4. PYMNTS: Shopify Opens Store Checkouts to AI Agents (September 28, 2026)
5. GeekWire: Amazon blocks Meta’s Muse AI assistant in new standoff over agentic shopping
6. PYMNTS: Shopify Brings Shop Pay Checkout Solution to Meta’s Muse AI Agent (September 22, 2026)