[BUG] Marketplace sync fails for all new marketplaces — "Some plugins in this marketplace have validation errors"

Preflight Checklist

• [x] I have searched existing issues and this hasn't been reported yet
• [x] This is a single bug report (please file separate reports for different bugs)
• [x] I am using the latest version of Claude Code

What's Wrong?

Marketplace sync fails with "Some plugins in this marketplace have validation errors" for any new marketplace, including a brand-new repo with a single minimal plugin. Previously synced marketplaces continue to work.

What Should Happen?

Marketplace sync fails with "Some plugins in this marketplace have validation errors" for any new marketplace, including a brand-new repo with a single minimal plugin. Previously synced marketplaces continue to work.

Steps to reproduce

1. Create a new private GitHub repo with the absolute minimum marketplace structure:

.claude-plugin/marketplace.json

{
  "name": "my-marketplace",
  "owner": { "name": "My Org" },
  "metadata": { "description": "Test marketplace", "version": "1.0.0" },
  "plugins": [
    {
      "name": "my-plugin",
      "source": {
        "source": "git-subdir",
        "url": "owner/repo",
        "path": "plugins/my-plugin"
      },
      "description": "Test plugin.",
      "version": "1.0.0"
    }
  ]
}

plugins/my-plugin/.claude-plugin/plugin.json

{
  "name": "my-plugin",
  "version": "1.0.0",
  "description": "Test plugin."
}

1. Go to Claude Desktop → Cowork → Customize → Add marketplace
2. Enter owner/repo or https://github.com/owner/repo
3. Click Sync

Expected behavior

Marketplace syncs successfully and the plugin appears.

Actual behavior

Sync fails immediately with:

Marketplace sync failed Some plugins in this marketplace have validation errors.

Key observations

• A marketplace that was synced before this issue started (delta-people-plugins) still works and can be re-synced successfully
• A brand new repo created today with an identical structure (single plugin, minimal config) fails to sync
• The marketplace.json and plugin.json are valid JSON and pass claude plugin validate locally
• This affects multiple repos, not just one — tested with 4+ different repos
• The error message gives no detail on which plugin or what the validation error is

Additional context

The working marketplace (delta-people-plugins) has the exact same structure: git-subdir source, minimal plugin.json with only name/version/description. The only difference is it was first synced before 2026-04-08.

Error Messages/Logs

Steps to Reproduce

Steps to reproduce
Create a new private GitHub repo with the absolute minimum marketplace structure:
.claude-plugin/marketplace.json

{
"name": "my-marketplace",
"owner": { "name": "My Org" },
"metadata": { "description": "Test marketplace", "version": "1.0.0" },
"plugins": [
{
"name": "my-plugin",
"source": {
"source": "git-subdir",
"url": "owner/repo",
"path": "plugins/my-plugin"
},
"description": "Test plugin.",
"version": "1.0.0"
}
]
}
plugins/my-plugin/.claude-plugin/plugin.json

{
"name": "my-plugin",
"version": "1.0.0",
"description": "Test plugin."
}
Go to Claude Desktop → Cowork → Customize → Add marketplace
Enter owner/repo or https://github.com/owner/repo
Click Sync

Claude Model

None

Is this a regression?

Yes, this worked in a previous version

Last Working Version

_No response_

Claude Code Version

2.1.72 (Claude Code)

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

Terminal.app (macOS)

Additional Information

_No response_