Hyvä Checkout Custom Field: A Working Delivery-Date Example
Most Hyvä checkout customization tutorials stop at "render a field" and skip the backend plumbing that actually persists the value to the order. Here is a complete, copy-pasteable delivery_date field for Hyvä Checkout 1.2+ on Magento 2.4.4-2.4.9: the Magewire vs Alpine.js decision tree, the extension_attributes.xml declaration, the Magewire component class, the date input partial with HTML5 min/max constraints, the QuoteRepository save plugin, and the admin sales_order_view.xml display. Plus the gotcha that breaks guest checkouts: the date does not survive submitQuote without a second plugin.