The lazy room wake handed caller-supplied ids to fileFor; an 8-char traversal like '../../aa' fit through the length trim. Only [A-Z0-9] codes reach disk now — reads refuse quietly, server-minted writes fail loud. Co-Authored-By: Claude Fable 5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_015RCWSTnb1KYTPyL4GmhGnF