Developer Zac said on X that Claude Opus 5.5, running autonomously through Claude Code, deleted his entire C drive; the post drew over one million views. He had used the --dangerously-skip-permissions flag and suspects a PowerShell syntax-joining error, but has not published full command logs, so it is unclear whether the model, the script or another step caused the deletion; he recovered about 98% of data from daily backups to a Synology NAS. Claude Code lead Boris Cherny responded that this is why Anthropic recommends Auto Mode, which assesses risk before execution and blocks destructive actions; Anthropic says Auto Mode has been the default for Pro, Max and Team users since August 14, 2026, and its internal test with 1,053 paying testers found humans caught only 13.6% of dangerous commands versus 89% for Auto Mode. Zac said Auto Mode often interrupts his tasks, and a Linux user reported losing a home directory with Auto Mode enabled, cutting against the claim.