claude-code - 💡(How to fix) Fix [BUG] Blender Connector Fails to Download/Run [1 participants]

Preflight Checklist

• I have searched existing issues and this hasn't been reported yet
• This is a single bug report (please file separate reports for different bugs)
• I am using the latest version of Claude Code

What's Wrong?

Official Blender connector v1.0.1 fails to install/run on Windows with deterministic error: error in 'egg_base' option: '.' does not exist or is not a directory. Failed to build blender-mcp via both uvx blender-mcp and uv run blender-mcp. Path is URL-encoded (Claude%20Extensions). Reproducible on fresh Blender 5.1.1 install with empty MCP config. Full log file available — extension and Blender add-on side both install successfully; failure is in uv's editable build of the bundled Python package.

mcp-server-blender.log

What Should Happen?

User should be able to download the extension and run it successfully.

Error Messages/Logs

Steps to Reproduce

Title: Connector install fails on Windows with egg_base error in setuptools build Environment:

OS: Windows 11 Blender: 5.1.1 (fresh install, .msi installer) Claude Desktop: latest (as of April 29, 2026) Connector version: 1.0.1 Blender add-on side: installed successfully via lab.blender.org drag-and-drop, server running on localhost:9876

Steps to reproduce:

Fresh Windows install of Blender 5.1.1 (default .msi installer). Install the Blender MCP add-on by dragging the install link from https://www.blender.org/lab/mcp-server/ into Blender twice. Verify it loads and the server auto-starts on localhost:9876. Open Claude Desktop. Go to Customize → Connectors, search Blender, click Install. Approve the "Do you want to install Blender?" dialog. Wait for "Installing..." to finish.

Expected: Connector installs successfully, MCP tools become available in Claude Desktop chats. Actual: "Extension Installation Failed" dialog with this error: The extension could not be installed due to the following error: uv.exe exited with code 1: Failed to build blender-mcp @ file:///C:/Users/<user>/AppData/Roaming/Claude/Claude%20Extensions/ant.dir.gh.blender.blender-mcp ├─▶ The build backend returned an error ╰─▶ Call to setuptools.build_meta.build_editable failed (exit code: 1)

[stdout] running egg_info

[stderr] error: error in 'egg_base' option: '.' does not exist or is not a directory

hint: This usually indicates a problem with the package or the build environment. Even after the dialog reports failure, the extension does eventually appear in Settings → Extensions (after ~1 hour in my case, possibly a retry). Enabling it produces the same error in MCP server logs and the server stays in a "failed / disconnected" state. Reproduces deterministically across two invocation paths:

cmd /c uvx blender-mcp uv run blender-mcp (after the extension auto-registered)

Both fail with the identical egg_base error. Likely cause: The package's setup.cfg or pyproject.toml likely declares [egg_info] egg_base = ., which resolves to uv's temp build CWD rather than the package source directory. Possibly compounded by URL-encoded path handling — note Claude%20Extensions (literal %20, not decoded space) appearing in uv's resolved file URL. Workarounds tried (none worked):

Quitting Claude Desktop fully (tray → Quit) and retrying Letting Claude Desktop sit and auto-retry (extension eventually appears but in failed state)

Note: The previous community connector (ahujasid/blender-mcp) installs and runs cleanly via uvx blender-mcp against the same Blender 5.1.1 install on the same machine, confirming the issue is in this connector's Python packaging rather than the local environment.

Claude Model

None

Is this a regression?

I don't know

Last Working Version

No response

Claude Code Version

2.1.121

Platform

Other

Operating System

Windows

Terminal/Shell

Other

Additional Information

No response