Try adding seller_message to failed order notes

includes/class-wc-payment-gateway-wcpay.php

@@ -1294,6 +1294,7 @@ public function process_payment( $order_id ) {
 				);
 
 				$error_details = esc_html( rtrim( $e->getMessage(), '.' ) );
+				$error_details = $error_details . '. ' . esc_html( rtrim( $e->get_merchant_message(), '.' ) );
 
 				if ( $e instanceof API_Exception && 'card_error' === $e->get_error_type() ) {
 					// If the payment failed with a 'card_error' API exception, initialize the fraud meta box

includes/compat/subscriptions/trait-wc-payment-gateway-wcpay-subscriptions.php

@@ -342,12 +342,15 @@ public function scheduled_subscription_payment( $amount, $renewal_order ) {
 			$renewal_order->update_status( 'failed' );
 
 			if ( ! empty( $payment_information ) ) {
+				$error_details = esc_html( rtrim( $e->getMessage(), '.' ) );
+				$error_details = $error_details . '. ' . esc_html( rtrim( $e->get_merchant_message(), '.' ) );
+
 				$note = sprintf(
 					WC_Payments_Utils::esc_interpolated_html(
 					/* translators: %1: the failed payment amount, %2: error message  */
 						__(
 							'A payment of %1$s <strong>failed</strong> to complete with the following message: <code>%2$s</code>.',
-							'woocommerce-payments'
+							'woocommerce-payments' // @todo
 						),
 						[
 							'strong' => '<strong>',
@@ -358,7 +361,7 @@ public function scheduled_subscription_payment( $amount, $renewal_order ) {
 						wc_price( $amount, [ 'currency' => WC_Payments_Utils::get_order_intent_currency( $renewal_order ) ] ),
 						$renewal_order
 					),
-					esc_html( rtrim( $e->getMessage(), '.' ) )
+					$error_details
 				);
 				$renewal_order->add_order_note( $note );
 			}

includes/exceptions/class-api-exception.php

@@ -23,17 +23,24 @@ class API_Exception extends Base_Exception {
 	/**
 	 * Error type attribute from the server.
 	 *
-	 * @var string
+	 * @var string|null
 	 */
 	private $error_type = null;
 
 	/**
 	 * Decline code if it is a card error.
 	 *
-	 * @var string
+	 * @var string|null
 	 */
 	private $decline_code = null;
 
+	/**
+	 * Merchant message. This message should not be shown to shoppers.
+	 *
+	 * @var string|null
+	 */
+	private $merchant_message = null;
+
 	/**
 	 * Constructor
 	 *
@@ -42,13 +49,15 @@ class API_Exception extends Base_Exception {
 	 * @param int        $http_code  HTTP response code.
 	 * @param string     $error_type Error type attribute.
 	 * @param string     $decline_code The decline code if it is a card error.
+	 * @param string     $merchant_message The merchant message. This message should not be shown to shoppers.
 	 * @param int        $code       The Exception code.
 	 * @param \Throwable $previous   The previous exception used for the exception chaining.
 	 */
-	public function __construct( $message, $error_code, $http_code, $error_type = null, $decline_code = null, $code = 0, $previous = null ) {
-		$this->http_code    = $http_code;
-		$this->error_type   = $error_type;
-		$this->decline_code = $decline_code;
+	public function __construct( $message, $error_code, $http_code, $error_type = null, $decline_code = null, $merchant_message = null, $code = 0, $previous = null ) {
+		$this->http_code        = $http_code;
+		$this->error_type       = $error_type;
+		$this->decline_code     = $decline_code;
+		$this->merchant_message = $merchant_message;
 
 		parent::__construct( $message, $error_code, $code, $previous );
 	}
@@ -79,4 +88,13 @@ public function get_error_type() {
 	public function get_decline_code() {
 		return $this->decline_code;
 	}
+
+	/**
+	 * Returns the merchant message.
+	 *
+	 * @return string|null Merchant message.
+	 */
+	public function get_merchant_message(): ?string {
+		return $this->merchant_message;
+	}
 }

includes/wc-payment-api/class-wc-payments-api-client.php

@@ -2358,8 +2358,13 @@ protected function check_response_for_errors( $response ) {
 				$error_message
 			);
 
+			$merchant_message = null;
+			if ( 'card_declined' === $error_code && isset( $response_body['error']['payment_intent']['charges']['data'][0]['outcome']['seller_message'] ) ) {
+				$merchant_message = $response_body['error']['payment_intent']['charges']['data'][0]['outcome']['seller_message'];
+			}
+
 			Logger::error( "$error_message ($error_code)" );
-			throw new API_Exception( $message, $error_code, $response_code, $error_type, $decline_code );
+			throw new API_Exception( $message, $error_code, $response_code, $error_type, $decline_code, $merchant_message );
 		}
 	}