You remember, and maybe this is the beginning of the problem:
You’d made plans that night. He’d bailed, for a reason. You’d semi-bailed, for a less good reason. You’d tried to meet up with each other, and finally you definitively bailed so that he would not have to leave his friends. Something external changes, you change your mind. You ask to come over. He tells you he is going to sleep. He tells you he is tired. He apologizes. It’s quite fine. You bid him goodnight, see you tomorrow.
Later, much later, you walk back to your room, run into his best friend, who mentions that he — your he — had left to meet up with a friend. That they are all going back to hang out with him. You are confused. You bid him goodnight. You walk and think, process: he lied to you. He gave details, false details, in order to spend time with someone other than you, in order to avoid you.
It is the details that cut you most. Such a simulacra of the real: an earnest him going to sleep, early. You would never have known, never would have had any inkling to suspect, were it not for sheer chance. It’s not that he lied; it’s that you couldn’t tell.
You confront him; he apologizes, admits, discusses. You accept. You accepted. But here you are in the now: months later, you are scrolling back to relive, remember, reprocess. That was how trust crumbles. This is how fissures form.