[BUG] "Failed to add marketplace" in Claude Desktop (Cowork) — missing `author` field in marketplace plugin entry

[hckhanh]

Description

When attempting to add CodSpeedHQ/codspeed as a plugin marketplace in the Claude Desktop app (Cowork mode), the operation fails with a generic error:

Failed to add marketplace.

No additional error details are shown to the user.

Steps to Reproduce

1. Open Claude Desktop app (Cowork mode)
2. Go to Directory → Plugins
3. Click "Add marketplace" (the + button)
4. Enter CodSpeedHQ/codspeed in the URL field
5. Click Sync
6. Error appears: "Failed to add marketplace."

Root Cause Analysis

The plugin entry in .claude-plugin/marketplace.json is missing the author field:

{
  "name": "codspeed",
  "source": "./",
  "description": "Tools for accurate and reliable performance measurement and optimization"
}

Claude Desktop's listAvailablePlugins validation schema requires the author field on plugin entries, even though the Claude Code CLI does not enforce this. This is a known issue affecting many third-party plugins (see anthropics/claude-code#33068).

Note: the plugin.json already has the author field, but the marketplace entry itself also needs it for the Desktop app's validation to pass.

Suggested Fix

Add the author field to the plugin entry in .claude-plugin/marketplace.json:

{
  "name": "codspeed-plugin-marketplace",
  "owner": {
    "name": "CodSpeed"
  },
  "plugins": [
    {
      "name": "codspeed",
      "source": "./",
      "description": "Tools for accurate and reliable performance measurement and optimization",
      "author": {
        "name": "CodSpeed"
      }
    }
  ]
}

Environment

• App: Claude Desktop (Cowork mode), macOS
• Date: 2026-04-01

[hckhanh]

Update: The root cause analysis in the original issue was incorrect.

After further investigation, the actual reason this fails is that Cowork's "Add marketplace" feature only supports private or internal GitHub repositories. Public repos like CodSpeedHQ/codspeed are explicitly blocked by design.

From the Cowork plugin management docs:

"Your repository must be private or internal — public repos aren't allowed for organization marketplaces."

This is a Cowork platform limitation, not a bug in this repository. The author field mentioned in the original report is unrelated to this failure.

Workarounds:

• Use Claude Code CLI instead: /plugin marketplace add CodSpeedHQ/codspeed (this works with public repos)
• Install the CodSpeed plugin via the official Anthropic marketplace if it's listed there

Closing this issue as it's not actionable on the CodSpeed side. Apologies for the noise — also closing the linked PR #283.

[hckhanh]

Update #2: Found the actual root cause — git-lfs is required.

The previous two analyses were both incorrect. The real issue is:

This repository uses git-lfs (see .gitattributes) for testdata/perf_map/*, *.gif, and large snapshot files. When a machine doesn't have git-lfs installed, cloning the repo fails silently during marketplace addition, and Claude Desktop/Code shows only the generic "Failed to add marketplace." error with no indication that git-lfs is the problem.

Proposed fix: Add a note to the README or plugin documentation mentioning that git-lfs is a prerequisite for cloning the repository and installing the Claude plugin marketplace. This would save other users from the same confusing error.

Reopening this as a documentation improvement request.