Gemini CLI MCP config: malformed JSON vs missing enablement file

Gemini CLI 0.63.0-preview.0, released September 29, 2026, distinguishes a missing MCP enablement config from malformed JSON. If your Sume server will not load, the first job is to tell which of the two you have: a settings file that fails to parse is a typo to fix, and a missing enablement config is a separate case.

The Gemini CLI line is from its GitHub releases page, read 2026-10-01. It is a preview release, so check your installed version before expecting it. The Sume entry shape is from the MCP quickstart and the existing Gemini CLI guide.

What does the preview release change?

Under MCP configuration the notes say it distinguished between missing enablement config and malformed JSON. The same release resolved infinite auth loops from file contention and keyring issues, and bounded tool output size. Only the first item concerns a config file that will not load.

What does a valid Sume entry look like?

In ~/.gemini/settings.json, Sume goes under mcpServers with httpUrl for streamable HTTP. Use the key from your environment, not pasted into the file.

{
  "mcpServers": {
    "sume": {
      "httpUrl": "https://mcp.sume.com/mcp",
      "headers": {
        "Authorization": "Bearer $SUME_API_KEY"
      }
    }
  }
}

How do I tell the two problems apart?

A parse error is a bug in your file; a missing enablement config is the other case the release now reports separately. Validate the JSON with any JSON checker, then confirm the server shows in gemini mcp list or /mcp.

Does OAuth work instead of a header?

Yes. OAuth and API keys says Sume accepts OAuth, with mcp:read required and mcp:write opt-in, or an API key as a bearer or x-api-key header. For an OAuth entry drop the headers block. An API-key session sees the full hosted tool set, so keep the key out of project files that get committed.