muxr v3.6.1 Fail loud on present-but-unparseable session files. compose_launch_command loaded campaign.md/log.md best-effort and collapsed a MISSING and a PRESENT-BUT-UNPARSEABLE file to the same empty default, so a one-character frontmatter typo silently relaunched a live session stripped of its composed HARNESS prompt and every campaign --add-dir path. Now ABSENT still degrades (archived-but-running) while PRESENT-BUT-UNPARSEABLE fails loud, naming the file: recycle pre-flights before the destructive flush, upgrade composes before the exit and skips loud, restore skips rather than de-fang. ADR 0006.