[BUG] Claude Code Desktop Doesn't Have /plugin Command and cannot add plugin marketplaces, Claude hallucinates about this a lot

Preflight Checklist

• [x] I have searched existing issues and this hasn't been reported yet
• [x] This is a single bug report (please file separate reports for different bugs)
• [x] I am using the latest version of Claude Code

What's Wrong?

Lots of documentation explains that "Claude" can use /plugin to add plugins or marketplaces, but /plugin is not a registered command on the Claude Code Desktop windows app. As best I can tell this command only works in the CLI client. This is poorly documented on the web and in the training data, but Claude can see that the /plugin command is not registered, and gives the user extensive hallucinated instructions and says official documentation is hallucinated.

Similar results happen if you're using the mobile app or website with a cloud environment.

What Should Happen?

Claude Code Desktop should provide functionality for installing marketplaces and custom skills from github, and that functionality should be documented.

Cloud environments should provide similar functionality and be documented.

Error Messages/Logs

Steps to Reproduce

Try to run any variant of /plugin in the Windows Claude Code Desktop app.
Ask Claude how to install plugins or plugin marketplaces.
Ask Claude to do a web search to find out how to install plugins.
Ask Claude specifically about Claude Code DESKTOP app.
No, Claude, not Claude CLI, Claude DESKTOP.

Claude Model

Opus

Is this a regression?

I don't know

Last Working Version

_No response_

Claude Code Version

latest desktop app

Platform

Anthropic API

Operating System

Windows

Terminal/Shell

Other

Additional Information

_No response_