Claude's Safety Downgrade Backfires: Wipes User's 700GB Home Directory

机器之心 · wechat · 2026-08-30

Developer Guillemot asked Claude Fable 5 to write a script sandboxing and cleaning /tmp. Because it involved file deletion, Anthropic's safety mechanism downgraded the model from Fable 5 to Opus 4.8, which ran safety tests. The tests correctly flagged the home directory as untouchable—but the cleanup step reused a variable from testing that held the home directory path, deleting it immediately after confirming it shouldn't be deleted: 700GB gone, a week of work lost, while /tmp stayed untouched.

Developers have long complained about the downgrade mechanism: false triggers on normal coding, degraded capability, and sticky downgrades persisting through sessions. The case exposes a paradox—routing "dangerous" tasks to weaker models makes errors more likely exactly where precision matters.

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