public void onError(final String phase, final String errorCode) {
                    try {
                        sendSseEvent(writer, "error", Map.of("phase", phase, "message", errorCode, "errorCode", errorCode));
                        if (logger.isDebugEnabled()) {
                            logger.debug("SSE error event sent. phase={}, error={}", phase, errorCode);
                        }

        } else {
            final String errorCode = UUID.randomUUID().toString();
            message = escapeJsonKeyValue("error_code:", errorCode);
            if (logger.isDebugEnabled()) {
                logger.debug("[{}] {}", errorCode, stacktraceString.get().replace("\n", "\\n"));
            } else if (status >= 500) {
                logger.warn("[{}] {}", errorCode, t.getMessage());
            }
        }

                    logger.warn("Failed to access Web API.", e);
                }
                message = e.getMessage();
            } else {
                final String errorCode = UUID.randomUUID().toString();
                message = "[" + errorCode + "] Failed to access to Web API.";
                if (statusCode >= 400 && statusCode < 500) {
                    if (logger.isDebugEnabled()) {