Hey, thanks for the report.
This isn’t a bug. Cloud agents add Co-authored-by: Cursor by design, and there isn’t a separate setting to turn it off yet.
The setting Cursor Settings > Agents > Attribution that you found in the desktop app only controls the Made-with: Cursor trailer for commits made via the IDE and CLI agents. Cloud agents browser-based run through separate server-side code and aren’t connected to that setting, so these are two independent mechanisms.
There’s already a feature request for this here: Allow Disabling Cursor as Co-Author In Cloud Agents
If you want this added, it’s best to leave a +1 and your use case there to increase visibility for the team. For now, there’s no way to disable the co-author for cloud agents.