embeddedEmbedded checkout (ECP 2026-08-25): the profile adds the embedded transport and every checkout carries an embedded binding, so a host can load its continue_url in an iframe with ec_version and take over payment credentials, address changes, payment instrument changes and links. White Orchid is redirect-only. REST and MCP stay. on flowers-embedded.ucpsandbox.com. The baseline store is flowers.ucpsandbox.com.