Supabase MCP in VS Code: "Failed to create authentication token" error?

Question

On Windows 10 with VS Code, Chrome, Node v20.17.0, and supabase-js 2.75.0, the Supabase MCP server logs Error getting token from server metadata: Error: Failed to create authentication token and repeatedly shows [info] Waiting for server to respond to 'initialize' request.... Going through "Authorize API access for Visual Studio Code" and then the URL-handler fallback both end with the same error. How can I get the Supabase MCP tools to authenticate and connect in VS Code?

Originally asked on GitHub: https://github.com/supabase/mcp/issues/159

AgentArmorHQ team · Accepted Answer

Status: still open. No official fix was released in this thread; a Supabase team member reproduced a successful connection and asked for the reporter's VS Code version, while several other users confirmed the same failure.

Workarounds that worked for commenters:

1. **Use the HTTP server with an account token** (comment 6). Replace the `supabase` entry in `mcp.json` with:

```json
"supabase": {
  "type": "http",
  "url": "https://mcp.supabase.com/mcp?project_ref=[YOUR_PROJECT_ID]",
  "headers": {
    "Authorization": "Bearer [YOUR_TOKEN_FROM_ACCOUNT]"
  }
}
```

The commenter reports "it works for me" and warns that if this lives in a local `mcp.json`, don't forget to gitignore it.

2. **Use npx with a Personal Access Token instead of the OAuth flow** (comment 8). Generate a PAT at `https://supabase.com/dashboard/account/tokens`, then configure:

```json
{
  "mcp": {
    "servers": {
      "supabase": {
        "command": "npx",
        "args": [
          "-y",
          "@supabase/mcp-server-supabase@latest",
          "--access-token",
          "YOUR_PAT_HERE"
        ]
      }
    }
  }
}
```

Optionally add `"--project-ref", "YOUR_PROJECT_REF"` to scope it to one project. The commenter says this connected immediately.

3. **Check for a hidden dialog button** (comment 7). After choosing the "different way" option, the popup on Ubuntu only showed copy/cancel buttons; dragging the dialog to the left revealed the "Open" button that completes the redirect back to VS Code.

General advice: both token-based configs store credentials in plain text in your editor config, so treat them as secrets and keep them out of version control.

AgentArmorHQ team · Answer

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

Followed the reproduction steps: start the server, click "Authorize API access for Visual Studio Code", click "Authorize...", then try the URL-handler fallback. The server still logged "Failed to create authentication token" and kept waiting on the `initialize` request.

Source: https://github.com/supabase/mcp/issues/159

AgentArmorHQ team · Answer

**What @gregnr tried on GitHub** (Worked)

A Supabase team member ran a fresh Supabase MCP connection from VS Code, completed the browser consent, and was redirected back to VS Code with tools listed successfully.

Source: https://github.com/supabase/mcp/issues/159#issuecomment-3392905730

AgentArmorHQ team · Answer

**What @ubeydtalha tried on GitHub** (Worked)

Switched the MCP config to the HTTP URL with an `Authorization: Bearer` header using a token from the Supabase account; reported as working.

Source: https://github.com/supabase/mcp/issues/159#issuecomment-3613052965

AgentArmorHQ team · Answer

**What @lance2k tried on GitHub** (Worked)

On Ubuntu, dragged the popup that only showed copy/cancel buttons to the left to reveal the hidden "Open" button, then completed the authorization.

Source: https://github.com/supabase/mcp/issues/159#issuecomment-3903767129

AgentArmorHQ team · Answer

**What @hasanfaesal tried on GitHub** (Worked)

Bypassed the OAuth flow by running `@supabase/mcp-server-supabase@latest` through npx with `--access-token <PAT>` in the VS Code MCP config; connected immediately.

Source: https://github.com/supabase/mcp/issues/159#issuecomment-3912964261

Supabase MCP in VS Code: "Failed to create authentication token" error?

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