fluentcart-cart-checkout

FluentCart cart and checkout

Keep the browser declarative: it may request an item, quantity, coupon, address, and method, but the server must resolve every price and eligibility decision.

Read checkout-contract.md before adding a custom item, fee, checkout field, or nonstandard client.

Use the actual transport

In Free 1.6.0 normal cart mutations use authenticated-by-nonce admin AJAX:

• action=fluent_cart_checkout_routes plus fc_checkout_action
• action=fluent_cart_place_order for order placement

The X-WP-Nonce header is accepted for action fluentcart or wp_rest. It provides CSRF intent, not user identity or object ownership. Anonymous checkout remains public.

The registered REST namespace contains checkout and public product routes, but no active core /cart/add, /cart/update, or /cart/remove route. Do not implement a headless client from generic documentation alone.

Extend cart items safely

Prefer normal ProductVariation items. For a custom/ghost item:

1. Resolve a server-owned offer from the requested opaque item ID.
2. Validate availability, currency, quantity, customer eligibility, and mode.
3. Return a complete normalized item/variation from the documented custom-item filters.
4. Recompute the item on every quantity/revalidation path.
5. Never accept item_price, subtotal, discount, recurring amount, tax class, downloadable entitlement, or product title as authoritative client values.
6. Add a stable discriminator to prevent unrelated custom items from merging.

Relevant surfaces include fluent_cart/cart/validate_custom_item, fluent_cart/cart_item_product_variation, and the custom-item quantity/change hooks in Cart/CartResource. Verify the exact callback arguments at 1.6.0 before registering.

Add fees through Cart

Use Cart::addFee() with a stable key and addon-owned source. Keep calculation pure and deterministic for the current cart context. Use removeFee() or removeFeesBySource() when the condition no longer applies. Amounts are integer minor units.