Vegan is on the menu, but the same kitchen also prepares what you avoid, so cross-contamination is possible. Tell staff what you react to, and ask how your dish is prepared before you order.
Xu's Cooking in Vienna's seventh district describes itself as a vegetarian Asian restaurant, where chef Xu cooks classic vegetarian dishes and plant based mock meat made mostly from soy, beans and tofu. The site says vegans can eat almost every dish and that the exceptions with egg or cheese are clearly marked on the menu. Tell the staff about your allergies, the kitchen has the final word.