Claude Desktop .mcpb extension disconnects because the packaged bundle is incomplete and uvx path handling is fragile

[abanoub-ashraf]

Hi, thanks for building this project.

I ran into a Claude Desktop installation issue with the provided .mcpb extension and wanted to report the root causes
clearly.

Problem

After installing the .mcpb in Claude Desktop, the server failed with:

MCP NotebookLM MCP Server: Server disconnected

What I found

There seem to be 2 separate issues in the current Claude Desktop extension packaging:

1. The generated .mcpb bundle was incomplete
   The built .mcpb only contained manifest.json and did not include a real bundled entrypoint/server file for Claude
   Desktop to execute.

Because of that, Claude Desktop disconnected immediately.

2. The extension assumes uvx is available on Claude Desktop’s PATH
   After fixing the bundle locally and adding a launcher, Claude Desktop still failed because it could not find uvx.

The log showed that Claude Desktop was launching the extension, but then stderr reported that uvx was required and not
available on PATH.

On macOS, Claude Desktop appears to run with a reduced PATH, so even if uvx is installed in a normal user location
like ~/.local/bin/uvx, the extension may still fail.

Why this matters

So the issue is not just user setup. The extension packaging/workflow is fragile in two ways:

• the .mcpb is not self-contained enough to run correctly
• the launcher depends on uvx being discoverable from Claude Desktop’s environment

Suggested fix

I think the Claude Desktop extension should:

• package a real entrypoint inside the .mcpb
• point manifest.json to that bundled entrypoint
• avoid assuming uvx is on PATH
• either detect common uvx install locations or provide a more self-contained launch strategy

Reproduction

1. Build/install the provided .mcpb
2. Install it in Claude Desktop
3. Start Claude Desktop / enable the extension
4. Observe Server disconnected

Extra context

In my case, once I rebuilt the extension with a bundled launcher and made the launcher resolve uvx more defensively,
the extension started working.

If helpful, I can also share the exact local patch I used to get it working.

Thanks again.

[jacob-bd]

Thanks for the incredibly detailed bug report @abanoub-ashraf!

You were spot-on with both diagnoses. We've implemented a fix for this that will go out in v0.4.1 (releasing shortly):

1. Self-contained bundle: The build_mcpb.py script now bundles a cross-platform Python launcher (run_server.py) inside the .mcpb zip archive alongside manifest.json.
2. Robust PATH resolution: The run_server.py launcher uses shutil.which and falls back to checking common installation paths (~/.local/bin, ~/.cargo/bin, /opt/homebrew/bin, etc.) across macOS, Linux, and Windows.
3. Official syntax: The manifest.json now uses "command": "python3" and "args": ["${__dirname}/run_server.py"] so Claude Desktop correctly references the unpacked installation directory.

Thanks again for helping make the extension more robust!