[BUG] claude plugin marketplace add is case-sensitive with no deduplication — different casing reinstalls existing marketplace

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?

claude plugin marketplace add correctly detects a duplicate when the casing matches exactly, but silently reinstalls the marketplace when the org/repo name is provided with different casing. GitHub org and repo names are case-insensitive, so Frankledo/claude-skills and FrankLedo/claude-skills refer to the same repository.

What Should Happen?

Org/repo names should be normalised (e.g. lowercased) before the duplicate check, so that re-adding a marketplace with different casing is correctly identified as already installed.

Steps to Reproduce

% claude plugin marketplace add FrankLedo/claude-skills
✔ Successfully added marketplace: fxl (declared in user settings)

% claude plugin marketplace add Frankledo/claude-skills
✔ Marketplace 'fxl' already on disk — declared in user settings

% claude plugin marketplace add FrankLedo/claude-skills
Cloning via SSH: git@github.com:FrankLedo/claude-skills.git
Refreshing marketplace cache (timeout: 120s)…
Cloning repository (timeout: 120s): git@github.com:FrankLedo/claude-skills.git
Clone complete, validating marketplace…
Cleaning up old marketplace cache…
✔ Successfully added marketplace: fxl (declared in user settings)

Step 2 (lowercase) is correctly detected as a duplicate. Step 3 (original correct casing) reinstalls rather than detecting the existing entry — likely because the cache lookup uses the string as provided rather than a normalised form.

Error Messages/Logs

No error — the reinstall completes silently.

Claude Code Version

_Latest_

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

zsh

Additional Information

_No response_