[BUG] /plugin command not recognized in CLI version 2.1.1 on Windows

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?

Bug Description

The /plugin command returns "Unknown slash command: plugin" in Claude Code CLI version 2.1.1, despite this command being documented as available since version 1.0.33.

Steps to Reproduce

1. Launch Claude Code CLI version 2.1.1 on Windows
2. Type /plugin or /plugin marketplace add anthropics/claude-code
3. Receive error: "Unknown slash command: plugin"

Expected Behavior

The /plugin command should open the plugin manager interface or execute the plugin marketplace command as documented.

Actual Behavior

Error message: "Unknown slash command: plugin"

Environment

• Claude Code Version: 2.1.1
• Platform: Windows (win32)
• Working Directory: C:\Users\byfro\OneDrive\Desktop\Test
• Shell: /usr/bin/bash
• Git Repo: No

Additional Context

• The /plugin command works correctly in Antigravity (web version)
• User confirmed they are running the latest version (2.1.1)
• Attempted commands:
• /plugin marketplace add anthropics/claude-code
• /plugin install frontend-design@claude-code-plugins
• All attempts result in "Unknown slash command: plugin"

Workaround

Currently using Antigravity (web version) where the plugin functionality works as expected.

What Should Happen?

Looking to install the below from Thariq (@trq2121)

To get started add our marketplace in Claude Code:

/plugin marketplace add anthropics/claude-code

and then install the plugin:

/plugin install frontend-design@claude-code-plugins

Error Messages/Logs

Nothing happens when I enter the commands above. It thinks, then it does nothing, no error code.

Steps to Reproduce

Steps to Reproduce

1. Launch Claude Code CLI version 2.1.1 on Windows
2. Type /plugin or /plugin marketplace add anthropics/claude-code
3. Receive error: "Unknown slash command: plugin"

Claude Model

Not sure / Multiple models

Is this a regression?

Yes, this worked in a previous version

Last Working Version

2.1.0

Claude Code Version

2.1.1

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

PowerShell

Additional Information

_No response_