Are you sure about the one char thing? I’d expect a huge flash if that was the case.

No, I'm not sure about the precise mechanics of it, but I noticed it because of the huge flash when using it over a somewhat laggy SSH connection. It doesn't happy in all contexts. I've definitely seen it when typing into the new-ish Claude "ask questions about the plan" flow, and I've also noticed that it redraws the entire conversation history when each new line of output is presented in a long-running tool call.