[BUG] Plugin `mcpServers` defined in `plugin.json` is never loaded at runtime

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?

MCP servers defined inline in a plugin's plugin.json manifest are silently ignored.
The .claude-plugin/ directory is not included in the plugin's runtime cache, so any
mcpServers configuration there is never read.

Actual Behavior

The MCP server is not loaded. Inspecting the plugin runtime cache
(~/.claude/plugins/cache/<marketplace>/<plugin>/<version>/) reveals that
.claude-plugin/ contents are absent — only commands/, skills/, hooks/,
and root-level files are present.

What Should Happen?

The MCP server defined in plugin.json should be loaded and appear as connected.

Error Messages/Logs

None

Steps to Reproduce

1. Create a plugin with mcpServers defined inline in .claude-plugin/plugin.json:

``json
{
"name": "my-plugin",
"mcpServers": {
"my-server": {
"type": "sse",
"url": "https://example.com/sse"
}
}
}
``

1. Install the plugin and restart Claude Code
2. Check /plugin → the MCP server does not appear as connected

Claude Model

Sonnet (default)

Is this a regression?

Yes, this worked in a previous version

Last Working Version

unsure

Claude Code Version

2.1.45

Platform

Anthropic API

Operating System

Other Linux

Terminal/Shell

VS Code integrated terminal

Additional Information

Workaround

Move mcpServers out of plugin.json and into a .mcp.json file at the plugin
root (alongside .claude-plugin/, not inside it):

my-plugin/
├── .claude-plugin/
│   └── plugin.json    ← name and description only
├── .mcp.json          ← MCP server definitions here
├── commands/
└── skills/

Environment

• Marketplace type: directory (local), also likely affects github-sourced marketplaces