Opus 4.7 Data Loss Crisis

34 bugs tracked. 50GB+ lost. 20+ incidents in 3 days. Published April 18, 2026.

What's Happening

50GB Permanently Deleted (#49129)

A user reported that rm -rf destroyed ~1,500 files and ~50GB of data permanently. The comments suggest PreToolUse hooks as prevention.

Auto Mode Safety Classifier: Two Critical Failures

Problem 1: Classifier hardcoded to Opus 4.6 (#49618). In Opus 4.7 sessions, the classifier can't start — all bash commands except reads are blocked. Development stops completely.

Problem 2: Classifier allows dangerous operations (#49554). Even when running, the classifier (Sonnet 4.6) approved rm -rf ~/.ssh, deleting all SSH keys.

Real Incidents

• #49539: ~/.git-credentials PATs deleted without confirmation
• #49615: Installer auto-update truncated ~/.bash_profile and ~/.zshrc to 0 bytes
• #49464: ./~ interpreted as ~/, triggering home directory deletion
• #48792 / #49102: macOS case-insensitive paths caused unintended directory deletion (2 incidents in 48 hours)

Token Consumption Exploding

1. 4x quota burn (#49601). Opus 4.7's new tokenizer generates up to 35% more tokens for the same text (Finout.io analysis).

2. System tokens inflated 1.7x (#49356). New session startup: 21.5K → 36.7K tokens. You're charged before typing anything.

3. cache_read billed at full rate (#49302). Anthropic support acknowledged pricing "doesn't match documentation."

4. Prompt cache destroyed every turn (#49585). Internal function smooshSystemReminderSiblings invalidates cache prefix matching. Effective consumption rate: ~5x normal.

Fix It: 3 Hooks

Claude Code hooks run at the process level — independent of the model. They work even when the classifier fails.

1. dotfile-protection-guard

Blocks Write/Edit to .bashrc, .ssh/*, .git-credentials, .npmrc, and other critical files.

2. auto-mode-safety-enforcer

Model-independent safety net. Blocks rm on critical paths and dotfile deletion via Bash, regardless of classifier state.

3. model-version-alert

Warns when Opus 4.7 is active. Checks every 50 tool calls — minimal performance impact.

Install All at Once

npx cc-safe-setup           # 8 core safety hooks
npx cc-safe-setup --opus47  # + 4 Opus 4.7 specific hooks

691 example hooks. 9,200+ tests. Open source: github.com/yurukusa/cc-safe-setup

Workarounds

• Pin to Opus 4.6: claude --model claude-opus-4-6
• Fix in settings.json: "model": "claude-opus-4-6"
• Disable auto mode until the classifier is fixed
• Back up critical files: cp -r ~/.ssh ~/.ssh.bak
• Thinking summaries gone? claude --thinking-display summarized (#49268)