[BUG] Desktop (Windows/MS Store): local stdio MCP server from an uploaded plugin stuck "Not connected" — Install button just opens the public Connector Directory

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?

I uploaded a local plugin (zip) via Settings → Plugins → "Upload plugin" in the Claude Desktop app for Windows (Microsoft Store install, MSIX package id Claude_pzs8sxrjxfjjc). The plugin declares a local stdio MCP server in .claude-plugin/plugin.json via mcpServers using ${CLAUDE_PLUGIN_ROOT} (command: python, args: server/server.py).

The plugin installs and shows as enabled, but on the plugin page → Connectors tab, the t2m-desktop-control connector is listed as not connected, with an "Install" button and the text "Connect each one so Claude can use them".

Clicking Install just opens the public Connector Directory. An uploaded/local plugin is naturally not listed there, so this is a dead end: there is no path in the UI to connect the plugin's own local server.

Result in sessions: the plugin's skill appears (skills don't depend on the server), but none of the plugin's MCP tools are available — the server never starts.

Steps to reproduce

1. Upload a plugin zip that declares a local stdio server in mcpServers (plugin used: https://github.com/LJCGJ/desktop-control, v0.8.2)
2. Open the plugin page → Connectors tab → the connector shows "not connected"
3. Click "Install" → the public Connector Directory opens (dead end)

Ruled out (it's not the plugin)

• Zip layout and .claude-plugin/plugin.json verified OK (mcpServers declared correctly)
• server.py compiles and starts cleanly outside the app (its audit log shows server_start version 0.8.2)
• Tried: toggling the plugin off/on, quitting the app from the tray and reopening, starting brand-new conversations — the connector stays "not connected"

Possible regression: earlier the same day (morning of Aug 10), with an earlier build of the same plugin on the same machine, the plugin's MCP tools DID work in sessions (they were even proxied to a cloud session by the device bridge). By the afternoon, after uninstall → upload of the new zip → restart, the connector was stuck "not connected". So either the connector had been auto-connected by another path before, or behavior changed.

Workaround: registering the server directly in claude_desktop_config.json works — noting that for the MS Store install the real file is at %LOCALAPPDATA%\Packages\Claude_pzs8sxrjxfjjc\LocalCache\Roaming\Claude\claude_desktop_config.json (not the classic %APPDATA%\Claude). Possibly related: #25600, #47819, anthropics/claude-ai-mcp#185.

Environment: Claude Desktop 1.26832.0.0 (Microsoft Store), Windows 11 Pro 25H2 (build 26200.8655), x64 — Dell Vostro 3400. Screenshots of the Connectors tab available on request.

What Should Happen?

Installing/enabling a plugin that declares a local stdio MCP server should start and connect that server automatically (or the Connectors tab should offer a working connect flow for it). The "Install" button should not redirect to the public Connector Directory for a locally uploaded plugin.

Error Messages/Logs

No error message is shown in the UI — the connector silently stays "Not connected" and the plugin's MCP tools never appear in sessions (while the plugin's skill does appear).

Steps to Reproduce

1. On Claude Desktop for Windows (Microsoft Store install), go to Settings → Plugins → "Upload plugin" and upload a plugin zip whose .claude-plugin/plugin.json declares a local stdio MCP server in mcpServers (e.g. https://github.com/LJCGJ/desktop-control, command python, args ${CLAUDE_PLUGIN_ROOT}/server/server.py)
2. Confirm the plugin appears in Settings → Plugins as installed and enabled
3. Open the plugin's page → "Connectors" tab
4. Observe the plugin's connector listed as "Not connected", with an "Install" button ("Connect each one so Claude can use them")
5. Click "Install" → the public Connector Directory opens instead of any connect flow for the plugin's local server (dead end)
6. Start a new conversation → the plugin's skill is listed, but none of its MCP tools are available
7. Toggling the plugin off/on, quitting via tray + reopening, and new conversations do not change anything

Claude Model

None

Is this a regression?

Yes, this worked in a previous version

Last Working Version

Unknown — plugin MCP tools worked on the morning of Aug 10 on the same machine; stuck "Not connected" since that afternoon (Desktop app)

Claude Code Version

N/A (Claude Desktop app 1.26832.0.0, Microsoft Store — not the CLI)

Platform

Other

Operating System

Windows

Terminal/Shell

Other

Additional Information

• This is about the Claude Desktop app (Cowork), not the CLI — the template's version/terminal fields don't quite apply (Desktop 1.26832.0.0, Microsoft Store install).
• Plugin repo (public): https://github.com/LJCGJ/desktop-control — plugin zip layout: .claude-plugin/plugin.json (+ server/, skills/), mcpServers declared with ${CLAUDE_PLUGIN_ROOT}.
• Screenshots of the Connectors tab ("Not connected" + Install button landing on the public Connector Directory) can be re-captured and attached on request.
• Possibly related: #25600 (local MCP servers ignored on MS Store installs), #47819 (plugin remote MCP connector fails to connect), anthropics/claude-ai-mcp#185 (plugin connector "Add" disabled).