[BUG] [Cowork] Two plugins with the same name: the slash menu shows two unlabeled entries, and in a local session both load the marketplace copy

Preflight Checklist

• [x] I have searched existing issues and this hasn't been reported yet (related: #94309, #95107)
• [x] This is a single bug report
• [x] I am using the latest version of Claude Code (Claude Desktop 2.19675.0 for macOS; agent 2.1.286 in the local session)

What's Wrong?

In a Team org, I had a plugin my-plugin installed from a marketplace (version 0.1.0), and I uploaded a private zip of a plugin with the same name (version 0.2.0). Customize → Plugins listed both, both enabled.

1. Two identical, unlabeled menu entries. Typing / and part of the skill name shows the skill twice. Nothing tells the user which copy each entry is.
2. Local session: the private copy can't be reached. In a local Cowork session, I picked each entry in turn (two new tasks). Both loaded the marketplace copy (0.1.0). The private copy had been delivered to the session: the session record lists both plugin ids, and both copies were staged on disk. It just could not be selected. (n=2, checked on disk.)
3. The two upload routes handle the clash differently. When the same-name plugin is in the Organization library, the upload shows a dialog: "A plugin with this name is already in your organization's library." and "Give yours a different name to keep both, or use the org's version above." The name field defaults to <name>-2. When the same-name plugin comes from a marketplace, the upload showed no dialog at all. (n=1 each.)

Disabling the marketplace copy in Customize fixed it: one menu entry, and the private copy loaded (n=1, local).

For comparison, a cloud session in the same org, with an Organization-library clash: the first menu entry loaded the private copy (n=1). Only the private copy was found in that container, though, so that run doesn't show whether both copies were delivered there.

What Should Happen?

Either refuse or rename a same-name upload consistently across both routes, or let the user tell the copies apart: label the menu entries by source (Local upload / Organization library / marketplace name), and make the chosen entry load that copy.

Error Messages/Logs

# None. The wrong copy loads silently.

Steps to Reproduce

1. In an org, install plugin my-plugin from a marketplace (version A) and enable it. Give its skill a line that prints the version, e.g. cat "${CLAUDE_PLUGIN_ROOT}/.claude-plugin/plugin.json".
2. Customize → Plugins → Upload a zip of a plugin with the same name in plugin.json, version B. (No dialog appears.)
3. Customize → Plugins now lists both, both enabled.
4. Start a new local Cowork task. Type / and part of the skill name: two identical entries appear.
5. Pick the first entry and send. Check which version the skill prints.
6. Start another new task, pick the second entry, and check again. In our run both printed version A.

Claude Model

Not model-related: the copy is chosen before the model runs.

Is this a regression?

I don't know

Claude Code Version

Agent 2.1.286, as staged by Claude Desktop 2.19675.0 (5706e5) for macOS. The agent version in the cloud container is not known.

Platform

Anthropic API (Claude subscription: Team plan)

Operating System

macOS

Terminal/Shell

Other: Claude Desktop app (Cowork)

Additional Information

• Team org: one local session (marketplace clash, n=2 tasks, disk-checked) and one cloud session (Organization-library clash, n=1).
• Related: #95107 (the menu and the runner read different copies of a plugin), #94309 (a typed /plugin:skill without the picker gives "Unknown skill"; we saw that here too, with and without a duplicate, so it is left out of this report).