Desktop app: "Could not load skill files" for custom marketplace plugins

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?

Description

Skills from custom marketplace plugins (registered via extraKnownMarketplaces) have two
issues in the Desktop app:

1. Skills panel: Skill names appear in Customize > Skills, but clicking any skill

shows:
Could not load skill files
Plugin not found: my-plugin@my-marketplace

1. Slash command menu: Skills do not appear in the autocomplete menu when typing /

in the prompt input. They are not discoverable through the UI at all.

Despite both issues, skills work correctly when the full command is typed manually in
the prompt box (e.g., /my-plugin:my-skill). They also work in the CLI.

What Should Happen?

Expected Behavior

• Skills should appear in the / autocomplete menu.
• Clicking a skill in the Skills panel of the "Customize" tab should show its SKILL.md content.

Actual Behavior

• Skills are absent from the / autocomplete menu.
• Skills panel in "Customize" tab shows "Plugin not found" when clicked.
• Skills execute correctly when the full command is typed manually.

Error Messages/Logs

Steps to Reproduce

1. Create a custom marketplace hosted in a git repository with one or more plugins

containing skills.

1. Register it in a project's .claude/settings.json:

{
  "extraKnownMarketplaces": {
    "my-marketplace": {
      "source": { "source": "git", "url": "https://example.com/my-org/my-marketplace.git"
}
    }
  },
  "enabledPlugins": {
    "my-plugin@my-marketplace": true
  }
}

1. Open the project in the Claude Code desktop app (Windows).
2. Type / in the prompt box - plugin skills do not appear in the autocomplete menu.
3. Open Customize > Skills panel - skill names are listed.
4. Click any skill.
5. Error: Could not load skill files - Plugin not found: my-plugin@my-marketplace
6. Type the full command manually (e.g., /my-plugin:my-skill) - it works.

Claude Model

Not sure / Multiple models

Is this a regression?

I don't know

Last Working Version

_No response_

Claude Code Version

2.1.85 (Claude Code)

Platform

Anthropic API

Operating System

Windows

Terminal/Shell

Other

Additional Information

Environment

• Platform: Windows 11 Enterprise
• Claude Code desktop app (native)
• Plugin is correctly registered in ~/.claude/plugins/installed_plugins.json with key

my-plugin@my-marketplace

Notes

• Likely related to #20593 - the skill content loader appears to use a different

resolution path than the skill executor.

• Also related to #18949 - skills from marketplace plugins missing from slash command

autocomplete.

• The plugin works perfectly in the CLI and when the full command is typed in the desktop

app's prompt box.

• Clearing the plugin cache (~/.claude/plugins/cache/) does not resolve the issue.
• Stripping unrecognized fields (repository, keywords) from plugin.json does not resolve

the issue.