Shopify customer merge fails: what the customerMerge docs say about blockers and gaps

A developer guide explains how to diagnose failed Shopify customer merges by checking userErrors, Customer.mergeable, and the customers/merge webhook. It notes that Shopify's documentation lists hard blockers such as subscriptions, store credit, and company contacts, but does not map every error code to a blocker. The customerMerge mutation rules determining which customer survives are summarized, along with its asynchronous job behavior and required access scope. The Help Center's nine profile-level merge blockers and the CustomerMergeErrorFieldType enum's 11 values are compared, with the author flagging mismatches and noting that merges are irreversible.