There is no single agentic checkout to tag. In-chat completion has no merchant page for gtag to fire. A Shopify ChatGPT path still hits your store checkout in an in-app browser. The GA4 job follows that split, and any source you write is a merchant convention.
Open rate and a Postmaster reputation badge no longer tell you whether a Shopify Klaviyo account is leaking. Read the signals that survived privacy changes, then fix integration, cart timing, segmentation and hygiene in that evidence order.
Once an AI recommendation layer is live, relevance-guessing rules can go. Constraints that protect cash should stay. Promote and kill SKUs on CM2, built as a reporting view from Shopify costs, not on conversion rate.