OptionalappliedLightweight captured email (no full customer record), or null.
OptionalexternalgetById/create/etc. (the carts resource) return this shape. See
CartSessionCart for the browser-facing CartSessionClient shape,
which omits workspaceId and adds cartId.
OptionallineOptionalselectedOptionaltaxSum of the line-item quantities — 1 stand + 2 notebooks + 1 keyboard is
4, not 3. Present only on this surface; the merchant carts resource
does not return it. Named for what it counts because itemCount in the
cart.abandoned webhook payload means the number of distinct lines.
The cart as the session (browser, opaque-token) surface returns it —
CartSessionClient's methods. There is noworkspaceIdon this surface (the browser never needs, and shouldn't see, the internal workspace id);cartId— the same value asid— is always present, kept for backward compatibility with@usethrottle/cart's original (order-snapshot-shaped) cart-session response.