Marketplace plugin skill gets silently mapped to official plugin skill instead of registering separately

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?

When installing a third-party marketplace plugin (Dammyjay93/interface-design) alongside the official frontend-design plugin, the marketplace plugin's skill is mapped to frontend-design:frontend-design instead of registering as its own skill entry (interface-design:interface-design).

The CLI confirms this on /reload-plugins:

"The interface-design plugin you enabled maps to the frontend-design:frontend-design skill in the available skills list."

What Should Happen?

Both skills should appear as separate entries in the skills list since they have:

• Different plugin names ("interface-design" vs "frontend-design" in plugin.json)
• Different skill directory names (skills/interface-design/ vs skills/frontend-design/)
• Different scopes (dashboards/admin panels vs marketing sites/landing pages)
• Different content and commands

Error Messages/Logs

The marketplace plugin's skill is merged into the official plugin. The interface-design SKILL.md content, its reference files, and its commands (`/interface-design:audit`, `/interface-design:critique`, `/interface-design:extract`) are not accessible.

Steps to Reproduce

Reproduction steps

1. Have frontend-design@claude-plugins-official enabled
2. Add marketplace: /plugin marketplace add Dammyjay93/interface-design
3. Enable it
4. Run /reload-plugins
5. Observe the mapping message and check /skills — only frontend-design:frontend-design appears

Claude Model

None

Is this a regression?

I don't know

Last Working Version

_No response_

Claude Code Version

2.1.91

Platform

Anthropic API

Operating System

Windows

Terminal/Shell

Other

Additional Information

Official (frontend-design):
.claude-plugin/plugin.json → { "name": "frontend-design" }
skills/frontend-design/SKILL.md

Marketplace (interface-design):

.claude-plugin/plugin.json → { "name": "interface-design" }
.claude/skills/interface-design/SKILL.md
.claude/commands/{audit,critique,extract,init,status}.md
references/{critique,example,principles,validation}.md

Additional context

The two plugins are designed to complement each other (the interface-design SKILL.md explicitly says "Not for: Landing pages, marketing sites, campaigns. Redirect those to /frontend-design"). The skill collision prevents using both as intended by the marketplace plugin creator.