Safeguards false positive: benign firmware CI/CD message flagged, session force-switched Fable 5 → Opus 4.8

Description

Fable 5's safeguards flagged a completely benign message in an ordinary software-engineering session, and the session was force-switched to Opus 4.8 ("Fable 5's safeguards flagged this message. This sometimes happens with safe, normal conversations. Switched to Opus 4.8.").

Context of the flagged message

The user message was a short instruction to implement two merge requests in parallel ("Do CI-hardening MR next and start PR 2 in 2 different tasks. They can be implemented in parallel"). The conversation topic: GitLab CI pipeline rules, static-library cross-compilation for an embedded target, and merge-request workflow. Nothing dual-use, nothing security-offensive — routine firmware/ML build engineering.

Expected

No flag; session stays on claude-fable-5.

Actual

Message flagged, model silently downgraded mid-session.

Environment

• Claude Code desktop app (macOS, Darwin 25.5.0)
• Model: claude-fable-5 (selected via /model)

Reporting per the in-product suggestion that this can happen with safe conversations — filing so the false-positive rate on plain DevOps/embedded content can be tuned.