Questioning my sexual orientation after a long-term friendship turned flirty

I've been best friends with someone for over six years. We always joked around and had a lot of inside jokes, but recently, the tone shifted - there’s been more teasing and flirty comments. It caught me off guard because I’ve never really thought of them in a romantic or sexual way before. I’m generally pretty sure I’m straight, and I’ve only dated people of the opposite gender. This new dynamic makes me question if my orientation might be more fluid than I assumed, or if it’s just a fleeting feeling because of the closeness we share. I’m trying not to rush into labeling myself differently without fully understanding it. But it’s confusing because I don’t want to hurt our friendship if I misinterpret things. Has anyone else experienced a shift in feelings toward a long-time friend that made them question their orientation? How did you navigate those emotions without risking the friendship? Also, how do you differentiate between genuine romantic interest and the comfort of deep friendship that feels like more?