My ex texted 'how are you'. What does he want?

“How are you?” asks about your present life. It does not explicitly ask to reunite or explain why your ex wrote now. Reading either intention into the greeting adds something the words have not yet said.

If you want to answer, you can keep the response as limited as the question and ask what prompted the contact. A polite exchange does not require you to decide the future of the relationship in the same message.