Unable to install plugin via Claude Code

[zhayes84]

I'm very sorry to bother you all but I've tried for 4 hours to install this plugin via Claude Code - to no avail.

I've attempted installation via SSH and HTTPS methods outlined and I cannot get Claude Code to install the plugin.

Upon running /plugin marketplace add addyosmani/agent-skills, Claude Code appears to correctly find the plugin on its marketplace.
When running /plugin install agent-skills@addy-agent-skills and selecting Install for you (user scope) or the other two options (project scope) or (local scope) I'm given this error:

Failed to install: Failed to clone repository: Cloning into
  'C:\Users\<user>\.claude\plugins\cache\temp_github_1781195903581_f6sois'...
  git@github.com: Permission denied (publickey).
  fatal: Could not read from remote repository.

  Please make sure you have the correct access rights
  and the repository exists.

I have my public SSH key in Github and can see it successfully upon running ssh -T git@github.com I successfully receive the response Hi zhayes84! You've successfully authenticated, but GitHub does not provide shell access.

I have been able to clone the repo locally to ~\.claude\plugins\marketplaces\addy-agent-skills but since it isn't an installed plugin within Claude Code, I cannot use the /spec command(s).

I'm so sorry if this is a dumb error on my part but I've done all I know to do. Claude Code runs in circles if I attempt to use it for diagnosis.

[nucliweb]

Hi @zhayes84, this is a known friction point on Windows. The plugin installer runs git clone in a subprocess that doesn't inherit the SSH agent, so even though ssh -T git@github.com works fine in your terminal, the key isn't available to Claude Code's internal git calls.

Quickest fix: rewrite SSH URLs to HTTPS

Run this once in your terminal:

git config --global url."https://github.com/".insteadOf git@github.com:

Then retry /plugin install agent-skills@addy-agent-skills. Git will use HTTPS instead of SSH, which works without an agent.

Alternative: enable the Windows OpenSSH Authentication Agent service

If you prefer to keep SSH:

1. Open Services (Win+R → services.msc)
2. Find OpenSSH Authentication Agent, set startup type to Automatic, then start it
3. Run ssh-add in a new terminal to register your key with the system agent
4. Retry the plugin install

Your manual clone may already work

You mentioned you cloned the repo to ~\.claude\plugins\marketplaces\addy-agent-skills. Claude Code may pick up the skills from there without a formal install; try running /spec or any other command and see if it works. If it does, the HTTPS fix above will let you keep things tidy via the official install flow.

Sorry for the friction, and thanks for the detailed report; the SSH agent inheritance issue on Windows is worth documenting better.