Set a draft order line's quantity
Authorizations
A secret API key. Publishable keys cannot reach this API. A key may carry an expiry, and an expired key is refused exactly like an unknown one, with a 401 that names no reason; check the key's expires_at in the dashboard rather than inferring it from a response. When a merchant rolls a key's secret they choose a grace window of up to 3 days, and for its duration BOTH the new secret and the one it replaced authenticate, so an integration moves over on its own deploy schedule instead of at the instant the button is pressed. Move before the window closes: after it, the old secret is refused. Nothing else about this contract moves with a roll. The key keeps its id and its scopes, so the only thing an integration updates is the credential itself.
Headers
A unique key per logical write. Replaying a request with the same key returns the first response byte for byte instead of applying the write twice.
Body
Sets an ABSOLUTE quantity, which is the difference from the add above: a reconciler that knows the buyer wants four sends four rather than a delta it would get wrong after a partial failure. Quantity is the only thing a line edit moves. variant_id is refused by name: the variant, the titles and the price were snapshotted when the line was added so an outstanding quote does not shift when the catalogue does. Remove the line and add the other variant instead.
The line's new quantity, replacing what was there.
x >= 1Response
Success
