Every partner is different. I'm by no means an expert here. I can only speak to my own experience. I don't think anyone has a magic detector, and I don't think any of the below is necessarily determinant.

In my experience, my partner: - had long expressed some concerns over his sexuality that he claimed they had resolved.
- waffled over time about whether or not he was bisexual. - expressed fears about being attracted to men and how his family wouldn't accept him if that was the case. - did not embrace typical gender norms. He was very liberal and attended pride events as an ally, including hanging out at a gay club. - had a difficult, infrequent sex life during our marriage that was filled with anxiety. - admitted to masturbating to gay porn at least a few times. - predominantly had female friends and referred to himself as one of the girls. - asked for an open relationship so that he could explore his same-sex attraction.

But honestly, despite the above, I didn't see it coming. I myself am bisexual, and I don't think that a partner expressing bisexuality means they're halfway to telling you they're gay. And I don't know that you can truly know until they sit you down and tell you that's the case. We all have a duty of honesty in our relationships. One of the reasons I created this sub was so that others know that if you don't see it coming, it's not your fault.