At what point to I mention I have a Boyfriend?

I like making friends so when I get a message from someone new I always chitchat with them. It usually happens to be guys- but I can never tell how soon I should be saying I’m in a relationship, or even how to say it 🙃 it stresses me out cause I don’t wanna jump to conclusions, but I also don’t want any miscommunication. Help? Lol
At what point to I mention I have a Boyfriend?
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