Add a GitHub marketplace to Claude Cowork or Claude Code

Anthropic's official catalog is the default, but any Git repository can be a plugin marketplace. Here is how to add one in Cowork (from Anthropic's current docs) and in Claude Code (tested on v2.1.296, October 2026).

In Cowork

Per Anthropic's docs: open Customize, then Plugins, and choose Add marketplace. Enter a GitHub repository as owner/repo or paste the full https://github.com/owner/repo URL. Its plugins then appear in the catalog next to the official ones and install the same way. Documented hosts: GitHub and GitHub Enterprise, plus public GitLab and Bitbucket.

Plugins need a paid Claude plan - if the Plugins page is missing entirely, that is the first thing to check (the full checklist is in plugin requirements).

In Claude Code

One command, verified on v2.1.296:

claude plugin marketplace add anthropics/knowledge-work-plugins ✔ Successfully added marketplace: knowledge-work-plugins

Then install from it with claude plugin install plugin-name@marketplace-name. The full tested sequence, including scope choices, is in install a plugin from a marketplace. Code also accepts any git URL or a local path as the source.

When the add fails

The two failures worth knowing, both reproduced:

• A repository you cannot access fails at the add step with git's own message about access rights - check the owner/repo spelling and whether the repo is private.
• A marketplace file that is invalid (for example, missing the required owner object) fails with a schema error naming the file - that is the marketplace author's to fix, not yours. Details in plugin validation failed.

A typo'd marketplace name later surfaces as a plugin-not-found error, not a marketplace error - the checks for that are in marketplace not found.

Sources

• Use plugins in Claude - Claude Help Center
• Plugins reference - Claude Code Docs
• Commands verified on Claude Code v2.1.296, October 11, 2026