A point of sale client integration platform is provided. The point of sale client integration platform includes a point of sale client application and a commerce client module that, in combination, provide a device agnostic payment transaction operation. The commerce client module includes communication interfaces, each of which corresponds to a particular communication protocol. The commerce client module receives a payment request from the point of sale client application and directly communicates, via one of the communication protocols, an authorization and capture request with respect to the payment request to a payment gateway. Through the same communication protocol, the commerce client module receives an authorization and capture response from the payment gateway. The commerce client module also drives a POS device to execute the device agnostic payment transaction operation in accordance with the payment request and the authorization and capture response.