Claude Code reserved MCP server name: widgets, and Sume's name

Claude Code 2.1.285 (September 29, 2026) reserves the MCP server name widgets in cloud sessions and on self-hosted runners. If you registered a server of your own under that name, or a close spelling such as widgets_, it no longer loads and the changelog says to rename it. Sume's documented command registers the server as sume, which is not that name.

The reserved-name change is from the Claude Code changelog; the Sume name is from the MCP quickstart, read 2026-09-30.

What exactly did Claude Code change?

The changelog entry reads: the MCP server name widgets is reserved in cloud sessions and on self-hosted runners; your own server under it, or a close spelling such as widgets_, no longer loads. It does not list other reserved names, so do not assume a list beyond that one.

What name should I give the Sume server?

The quickstart adds it as sume and then signs in with claude mcp login sume:

claude mcp add --transport http sume https://mcp.sume.com/mcp
claude mcp login sume

Does the server name change the tool names?

Yes, on the client side. Sume's tool ids are underscore names such as tools_list. Sume's own server notes say some clients namespace tools as <server>-<tool> and that this form never reaches the server. Claude Code allow rules in the mcp__sume__tools_list form therefore depend on the name you chose, so renaming a server means updating its rules. See allowing MCP tools in Claude Code.

What if my own server was called widgets?

Pick a different name and re-add it, then update any allow or deny rules that mention the old prefix. Sign in again under the new name for a server that uses OAuth.