MCP servers fail when venvs don't exist in ~/.claude/plugins/marketplaces/. Claude Code doesn't run setup.sh when installing marketplaces, so users must run it manually. Added: - Critical warning section at top of UPDATING.md - Step to run setup in installed location after updates - Troubleshooting for "X MCP servers failed" error Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>