Skills from third-party marketplace plugins not loaded into context

Description

Skills defined by third-party marketplace plugins are not loaded into the session context, even when the plugin is enabled in settings.json. Official marketplace plugin skills load correctly.

Expected behavior

A skill from an enabled third-party marketplace plugin should appear in /context under "Skills > Plugin" and be available for invocation, the same as skills from official plugins.

Actual behavior

• Official plugin skills (commit-commands:commit, feature-dev:feature-dev, code-review:code-review, etc.) appear under Skills > Plugin in /context ✓
• Third-party plugin skill (andrej-karpathy-skills:karpathy-guidelines) does not appear in /context at all ✗
• The skill is not listed in the system-reminder skills block sent to the model ✗
• The skill cannot be invoked because the model has no awareness of it

Steps to reproduce

1. Install a plugin from a third-party marketplace that provides skills (e.g., andrej-karpathy-skills from karpathy-skills marketplace)
2. Confirm it is enabled in ~/.claude/settings.json:

``json
"enabledPlugins": {
"andrej-karpathy-skills@karpathy-skills": true
}
``

1. Confirm the plugin files exist with correct structure:

``
~/.claude/plugins/marketplaces/karpathy-skills/
├── .claude-plugin/
│ ├── marketplace.json
│ └── plugin.json # declares skills: ["./skills/karpathy-guidelines"]
├── skills/
│ └── karpathy-guidelines/
│ └── SKILL.md # has name/description frontmatter
└── ...
``

1. Start a new Claude Code session
2. Run /context — the skill does not appear under Skills > Plugin

Environment

• Linux (6.19.0)
• Claude Code with alwaysThinkingEnabled: true
• Plugin installed via third-party marketplace (not claude-plugins-official)
• Plugin cache exists at ~/.claude/plugins/cache/karpathy-skills/andrej-karpathy-skills/1.0.0/

Notes

This is distinct from #22112 (autocomplete-only). Here the skill is not loaded into context at all, not just missing from autocomplete. The distinguishing factor appears to be official vs third-party marketplace origin.