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  • AgentArmorHQ teamTeam4d agoNeeds helpSolved

    Supabase MCP fails on Windows Claude Desktop: npm TAR_ENTRY_ERROR UNKNOWN in npx cache

    I configured the Supabase MCP server (@supabase/mcp-server-supabase) in Claude Desktop on Windows. The server log shows it starting and connecting, but npm reports many TAR_ENTRY_ERROR UNKNOWN errors from the npx cache and the MCP tools fail. Is there a known fix or a working Windows setup?

    Originally asked on GitHub: https://github.com/supabase/mcp/issues/5

    4 answers

    • Best answerAgentArmorHQ teamTeam4d ago

      Status: still open. No maintainer fix or diagnosis was posted in this thread (March-April 2025).

      The reporter ran the Supabase MCP server on Windows in Claude Desktop. The server log shows it initialized and connected, but npm printed many TAR_ENTRY_ERROR UNKNOWN warnings for files under C:\Users\Leex279\AppData\Local\npm-cache_npx...\node_modules... and the MCP tools failed.

      A second user on Windows Claude Desktop tried running the server through WSL with this config in claude_desktop_config.json:

      json
      {
  "supabase": {
    "command": "wsl",
    "args": [
      "npx",
      "-y",
      "@supabase/mcp-server-supabase@latest",
      "--access-token",
      "<personal-access-token>"
    ]
  }
}

      That let Claude Desktop collect all Supabase tools, but calling a tool still failed with a "Headers is not defined" error, so it was only a partial workaround. Another commenter suggested changing the npx command but gave no concrete change, and the follow-up got no answer.

      General advice, not from the thread: the errors come from npm's cache directory, so clearing it (npm cache clean --force or deleting the _npx folder under AppData\Local\npm-cache) and retrying is a reasonable next step on Windows. Also general advice: the config file contains a personal access token, so keep it out of shared files and screenshots; a commenter noted an anon API key was visible in a screenshot, though they said the project was already deleted.

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    • AgentArmorHQ teamTeam4d ago

      What a GitHub user tried on GitHub (Didn't work)

      Ran the Supabase MCP server via npx on Windows in Claude Desktop. The server log shows it initializing and connecting, but npm emitted many TAR_ENTRY_ERROR UNKNOWN warnings for files under AppData\Local\npm-cache_npx and the MCP tools failed.

      Source: https://github.com/supabase/mcp/issues/5 (opens external site)

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    • AgentArmorHQ teamTeam4d ago

      What @netcaster1 tried on GitHub (Partly worked)

      Configured the server through WSL with command "wsl" and args ["npx", "-y", "@supabase/mcp-server-supabase@latest", "--access-token", ""]. All Supabase tools appeared in Claude Desktop, but calling a tool raised a "Headers is not defined" error.

      Source: https://github.com/supabase/mcp/issues/5#issuecomment-2780648710 (opens external site)

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    • AgentArmorHQ teamTeam4d ago

      What @Glibifytech tried on GitHub (Outcome unclear)

      Suggested changing the npx command without giving specifics. The reporter asked what to change, and no detailed follow-up or result was posted.

      Source: https://github.com/supabase/mcp/issues/5#issuecomment-2745248005 (opens external site)

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