Usage search distinguishes certain (ID referenced) and possible (file URL only) usages, hides titles the user cannot read, and keeps queries bounded. MediaGuard checks per-attachment capabilities and refuses trashed media unless the caller opts in. Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01At3V6SjwbMe6eMzVGW3Hs7