[BUG] SSH marketplace add error message hardcodes "GitHub" regardless of host

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?

When /plugin marketplace add <ssh-url> fails SSH authentication against a non-GitHub host, Claude Code emits an error message that references "GitHub" even though the target host is something else.

Verified reproduction (Claude Code, 2026-05-26):

/plugin marketplace add git@gitlab.com:gitlab-org/gitlab.git

(after seeding gitlab.com into known_hosts via ssh -T -o StrictHostKeyChecking=accept-new git@gitlab.com, with no SSH key configured for GitLab)

Surfaces:

Error: Failed to clone marketplace repository: SSH authentication failed. Please ensure your SSH keys are configured for GitHub, or use an HTTPS URL instead.

Note: a separate SSH error branch — the "host key not in known_hosts" path — is already host-aware (correctly names the target host in its hint). Only the authentication-failure branch still hardcodes "GitHub".

What Should Happen?

The error message should reference the actual hostname parsed from the URL, e.g.:

SSH authentication failed. Please ensure your SSH keys are configured for gitlab.com, or use an HTTPS URL instead.

Or use host-agnostic phrasing matching the recently-improved host-key branch.

Error Messages/Logs

Steps to Reproduce

1. Make sure no SSH key is configured for gitlab.com in your SSH agent or ~/.ssh/config. (Any non-GitHub host you don't have an SSH key for works; GitLab is just convenient.)

1. Seed the host key into known_hosts so the SSH layer gets past the host-key check and into authentication:

``bash
ssh -T -o StrictHostKeyChecking=accept-new git@gitlab.com
``

Expected: Permission denied (publickey). — that's fine, we just need the host key cached.

1. Inside claude, run:

``
/plugin marketplace add git@gitlab.com:gitlab-org/gitlab.git
``

1. Observe the error message.

Claude Model

None

Is this a regression?

I don't know

Last Working Version

_No response_

Claude Code Version

2.1.150

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

Terminal.app (macOS)

Additional Information

_No response_