[Cowork/claude.ai] Cannot add anthropics/claude-plugins-community as a marketplace; community plugins (e.g. eli5) missing from the directory

Summary

Community plugins such as eli5 can be installed via Claude Code CLI, but there is no working path to install them on claude.ai / Cowork.

What I tried (claude.ai web, Pro plan, 2026-09-02)

1. Customize > Plugins > Browse: searched "eli5" — no results.
2. Customize > Plugins > Add > Add marketplace > From repository: entered anthropics/claude-plugins-community (also the full https URL) — "Failed to add marketplace."
3. Workaround that worked: packaged the plugin folder (plugin.json + skills/eli5/SKILL.md) as a .plugin file and used "Upload plugin".

Likely cause

.claude-plugin/marketplace.json in the community repo lists eli5 with a relative source ("source": "./eli5"). The claude.ai/Cowork server-side sync resolves each plugin source independently and cannot resolve relative paths (documented under "Plugins with relative paths fail in URL-based marketplaces"). The repo also has 2,282 entries.

Note: the repo README says PRs/issues there are not accepted (read-only mirror) and points Cowork users to claude.com/plugins — but the plugin is not listed there either.

Requests (any of these would help)

• List community-approved plugins like eli5 in the claude.ai / claude.com plugin directory.
• Let the server-side sync resolve relative sources for the official community marketplace.
• Show the actual sync error instead of the generic "Failed to add marketplace."

Environment

claude.ai web (Chrome, macOS), Pro plan

Related: #61271, #28125