Context: I am visiting a high school friend. Another friend who we both knew in high school has posted some interesting things recently. This friend has changed their name, but the friend I am visiting is not following them and is not aware of their transition.
How do I bring up this friend without dead naming them?
Maybe best to ask the friend who has changed their name what they'd prefer you to do?
To be clear, their transition has been quite public and there is no question of acceptance by this friend. It is simply a circumstance of lives going in different directions that these two people are not actively friends and there is not a safety question.
Edit: I see your edit and obviously this is an easy solution given infinite time, but tends to break the flow of conversation…
I know not all transitions are the same but is there a general rule for this sort of situation.
just use their old name once when introducing the new name
Yeah this is the answer. It's okay to dead name when you're telling someone of a name change. After that, correct them every time if they don't use their new name.