Shopify Storefront cart attributes and notes via cartAttributesUpdate and cartNoteUpdate

In-depth guide

Steps

1. Use cartAttributesUpdate to attach an array of AttributeInput objects (key-value string pairs) to the cart; these flow through to the resulting order's attributes.
2. Use cartNoteUpdate to set a free-text note on the cart that will appear on the resulting order as the order note.
3. Keep attribute keys namespaced (e.g., prefixed with your app name) to avoid collisions with other integrations writing to the same cart.
4. Read cart.attributes and cart.note back in the mutation response to confirm the values were stored.
5. Query these fields later by fetching the cart by ID using the cart query to verify persistence across sessions.
6. Consult current Shopify docs for any length limits on note text and the maximum number of attribute key-value pairs allowed per cart.