One of my co-workers, who is sitting next to me, is also working with me on the same project that I'm working on. The leadership people from the client's team are chatting with me about the project and the team's performance.
When ever I'm chatting with the clients, most of the time my co-worker moves his chair to my desk and looks at my chat history. Mostly it relates to sprint estimation and planning, so I don't mind it. But sometimes I need to share about the team mate's performance.
I don't want him to see my chat details, so now some days when I'm chatting with the clients, if he moves to my desk I will minimize my chat window, though he will understand that situation and won't do it again. But he keeps repeating the same again.
Sometimes it's very frustrating and I don't want to show my anger to him. Is there a polite way to inform him that he should not look at my chat details?