Custom Restriction: Category-Specific Subtotal

add_filter( 'woocommerce_coupon_is_valid', 'custom_category_subtotal_coupon_gate', 20, 2 );

  function custom_category_subtotal_coupon_gate( $valid, $coupon ) {

      $target_coupon = 'your-coupon-code'; // lowercase coupon code

      $threshold     = 5000.00;

      $category_ids  = array( 12, 34 ); // replace with actual product category IDs

      if ( strtolower( $coupon->get_code() ) !== $target_coupon ) {

          return $valid;

      }

      if ( ! WC()->cart ) {

          return false;

      }

      $category_subtotal = 0.0;

      foreach ( WC()->cart->get_cart() as $item ) {

          foreach ( $category_ids as $cat_id ) {

              if ( has_term( $cat_id, 'product_cat', $item['product_id'] ) ) {

                  $category_subtotal += wc_get_price_excluding_tax(

                      $item['data'],

                      array( 'qty' => $item['quantity'] )

                  );

                  break;

              }

          }

      }

      if ( $category_subtotal < $threshold ) {

          throw new \Exception(

              sprintf(

                  'You have not met the %s%s minimum spend on qualifying categories.',

                  get_woocommerce_currency_symbol(),

                  number_format( $threshold, 2 )

              )

          );

      }

      return $valid;

  }