There are many synonyms for the phrase "are wise to someone", which means that someone is knowledgeable about another person's intentions or actions and is therefore cautious or careful around them. Some similar phrases include "have their number", "know someone's game", "keep their guard up", "are onto someone", "seeing through someone", "have insight into someone", and "are mindful of someone's motives". Each of these phrases implies a sense of suspicion or skepticism about the other person's intentions, as well as a sense of caution and awareness on the part of the speaker. Together, they suggest a sense of shrewdness and perceptiveness when it comes to understanding other people's behavior.