`npm install -g` can succeed while the binary lands in a prefix that isn't on the current shell's PATH (common with Homebrew, nvm, or an unconfigured npm prefix). Re-probe via `which gsd-sdk` (or `where` on Windows) after install; if it doesn't resolve, downgrade the success message to a warning with a shell-restart hint. Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>