error: unknown option '-s' from `claude mcp add <name> -s user -- docker run ... -p 127.0.0.1:8085:8085 ...`

Context

Source(s): https://github.com/anthropics/claude-code/issues/79638 Status: source reports fixed; not reproduced by us.

Problem

Adding a Docker-based MCP server whose command publishes a port with docker's short -p flag fails with unknown option '-s', even though the docker args come after --. This blocks the documented Docker local setup for some MCP servers (e.g. GitHub's MCP server).

Error (redacted / normalized)

error: unknown option '-s'

Applies when

Claude Code CLI before v2.1.239 (reproduced on 2.1.233), adding a Docker-based stdio MCP server.

Confirm it is this problem

(our note) claude --version is below 2.1.239 and the docker args after -- contain -p.

Not this when / boundary

The flag named in the error really is placed before --.

Root cause

The CLI's early scan for its own -p/--print flag didn't stop at the -- separator, so docker's -p was read as a Claude Code flag. A collaborator reproduced it on 2.1.233.

Fix

1. Upgrade Claude Code to v2.1.239 or later, where the scan stops at --. → expect: the add command succeeds ("Added stdio MCP server ...").
2. On versions before 2.1.239, use docker's long form --publish instead of -p (tested by the reporter and reproduced by a collaborator).

How to verify

claude mcp add testA -s user -- docker run -i --rm -p 127.0.0.1:8085:8085 alpine adds the server instead of erroring (a collaborator verified this on the fixed build).

What did not work

Not listed in the source.

Verified scope

Claude Code < 2.1.239 affected; fixed in 2.1.239 (Oct 2026)