[BUG] $CLAUDE_PLUGIN_ROOT not substituted in user-invocable (slash command) skills

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?

Plugin skills using disable-model-invocation: true (user-invocable/slash command skills) do not get ${CLAUDE_PLUGIN_ROOT} replaced with the actual cache path. Agent-invocable skills in the same plugin work correctly.

What Should Happen?

Both skill types should substitute ${CLAUDE_PLUGIN_ROOT} in the skill content with the cached plugin path.

Error Messages/Logs

Steps to Reproduce

• Install a plugin from a local directory marketplace (e.g. "source": "directory")
• Have two skills in the same plugin, both using ${CLAUDE_PLUGIN_ROOT} in their SKILL.md, one with disable-model-invocation: true, one without
• The agent-invocable skill resolves paths to ~/.claude/plugins/cache/... (correct)
• The user-invocable skill resolves paths to the source directory (incorrect), and its "Base directory" header also shows the source path

Claude Model

Opus

Is this a regression?

I don't know

Last Working Version

_No response_

Claude Code Version

2.1.85

Platform

Anthropic API

Operating System

Ubuntu/Debian Linux

Terminal/Shell

Windows Terminal

Additional Information

This seems to be related to a number of reported issues re: CLAUDE_PLUGIN_ROOT:
#38699
#42564