Try changing the system prompt or switch to opencode [0] - they allegedly reverse engineered Claude Code, and so the performance you get with Claude models should be very similar to Claude Code.
I've changed the settings and added the instruction to the prompt, hence my frustration :)
there's an option for claude to disable co-authoring, see: https://code.claude.com/docs/en/settings
{ "includeCoAuthoredBy": false }