Researcher Dhruv Walia sent Claude, GPT and Gemini agents to buy one item from 500 well-known US online stores, stopping at the card form. He says 37% of stores stopped the agent (175 of 469 scored for Claude), rising to 73% of sites in the top 10,000 by traffic (55 of 75). Agents that were let in reached payment 93% of the time (272 of 294).
Shopify stores rarely stopped agents compared with other platforms of similar popularity, for example 0 of 17 against 63 of 88 in the top 50,000. The author says that is a pattern, not proof of cause. He also found 97 of 124 Shopify stores registered in-browser agent tools that roughly halved the actions needed to reach payment.
The detail to act on: when a paid add-on was on the page at payment, it ended up in the cart 29% of the time (47 of 162 runs), and 43 of those were because the store had pre-ticked it.
Keep the caveats in mind. It is one person's study, US stores only, from one home connection over one month, and popularity is web traffic, not revenue.