You'll notice
Teammate names "user" and "system" are now reserved alongside "main" and "team-lead"
What
When setting up a team of Claude Code teammates, certain names are reserved because they'd collide with special recipients. The error shown when a teammate's name conflicts with a reserved name now lists "user" and "system" as reserved, in addition to the existing "main" and "team-lead" (in any capitalization).
Why
This stops a teammate from being named something that would be ambiguous with the built-in "user" or "system" recipients.
Names in the bundleusersystem