Check Plugin Version

Verify the installed compound-engineering plugin version matches the upstream plugin.json on main, and recommend the update command if it doesn't. Claude Code only.

Pre-resolved context

Only the Skill directory determines whether this session is Claude Code — if empty or unresolved, the skill requires Claude Code. The other sections may contain error sentinels even in valid Claude Code sessions; the decision logic below handles those cases.

${CLAUDE_SKILL_DIR} is a Claude Code-documented substitution that resolves at skill-load time. For a marketplace-cached install it looks like ~/.claude/plugins/cache/<marketplace>/compound-engineering/<version>/skills/ce-update, so the currently-loaded version is the basename two dirname levels up.