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.
The entry above is what we published on the day. These lines were added later, as Anthropic's own pages caught up, and they sit beside the original rather than replacing it.
Added since
A small documentation edit on Delivering work touched a line naming system after this was published.
Claude Fable 5.1's writing has few stock phrases and little unexplained jargon. In some cases, though, its prose is denser than Claude Fable 5's: sentences run longer and there are fewer paragraph breaks. An instruction that defines the an…build-with-claude/prompt-engineering/prompting-claude-fable-5-1 see the edit
Added since
A small documentation edit on Delivering work touched a line naming user after this was published.
Claude Fable 5.1's writing has few stock phrases and little unexplained jargon. In some cases, though, its prose is denser than Claude Fable 5's: sentences run longer and there are fewer paragraph breaks. An instruction that defines the an…build-with-claude/prompt-engineering/prompting-claude-fable-5-1 see the edit
Confirmed since
Anthropic's documentation has since written up user, on Admin controls.
* **Another company's product**: the company that makes the product usually builds and runs its connector, not Anthropic. Check the [Connectors Directory](/docs/connectors/directory) first. If the company offers a connector that isn't list…claude-science/admin-controls see the edit
Confirmed since
Anthropic's documentation has since written up system, on Admin controls.
* **Your own systems and data**, such as an internal database or lab system: have your developers build a connector for it, then add its web address for everyone under **Organization settings > Connectors > Add > Custom** (see [Third party…claude-science/admin-controls see the edit
One source agreesOne thing we can check says the same as this entry.
Anthropic's documentation agrees
Anthropic's documentation has since written up system, on Admin controls.