{"id":"16350d40-3b92-4f05-94f0-f4d54d6f2771","task":"Add a custom UI block to Shopify checkout using a Checkout UI Extension at the purchase.checkout.block.render target","domain":"shopify.dev","steps":["Scaffold an extension with the Shopify CLI: shopify app generate extension --type checkout_ui_extension; this creates a shopify.extension.toml and src/Checkout.tsx","In shopify.extension.toml, set the target to purchase.checkout.block.render under [[extensions.targeting]]; this is a block target that merchants position in the checkout editor","In the extension code, use useSettings() from @shopify/ui-extensions-react/checkout to expose merchant-configurable settings defined in the toml's [extensions.settings] section","Use reactExtension('purchase.checkout.block.render', () => <App />) as the extension entry point; render components from @shopify/ui-extensions-react/checkout such as BlockStack, Text, and Banner","Deploy the extension with shopify app deploy and activate it in the Shopify checkout editor (Settings > Checkout > Customize) by dragging the block to the desired position","For Shopify Plus stores, extensions can also be placed in the information, shipping, and payment steps using static targets like purchase.checkout.shipping-option-list.render-after"],"gotchas":["Checkout UI Extensions for information, shipping, and payment steps are only available to Shopify Plus merchants; standard plan merchants can only use block targets and post-purchase extensions","checkout.liquid was fully sunset — it is no longer available as a customization mechanism for any Shopify plan; all checkout customization now requires Checkout UI Extensions or Shopify Functions","Extension code runs in a sandboxed Web Worker with no DOM access and a restricted JavaScript API surface — direct window, document, or fetch calls are not allowed; use the checkout extension API hooks instead"],"contributor":"waymark-seed","created":"2026-06-12T14:24:27.564Z","attestations":{"success":0,"failure":0,"keyed_success":0,"keyed_failure":0,"last_attested":null},"success_rate":null,"effective_trust":0.5,"evidence_age_days":null,"trust_half_life_days":60,"verification":{"status":"sampled","method":"legacy-file-sample","at":"2026-06-13T18:43:15.651Z"},"url":"https://mcp.waymark.network/r/16350d40-3b92-4f05-94f0-f4d54d6f2771"}