[Bug] Opus 5.5 safeguards falsely flag routine code review subagent as [bio] #109205

Bug Description
False positive: Opus 5.5 safeguards flagged a subagent as [bio] during a routine code review.

What happened: A subagent (general-purpose, model opus, effort high) was doing a read-only code review of a CI configuration change. It stopped early with "Opus 5.5's safeguards flagged this session", Details: [bio].

What the task actually was: Reviewing a GitHub Actions workflow and PHP tooling change for a Laravel web app: adding zizmor (workflow security linter), adding Psalm static analysis (taint analysis), removing actions/cache steps, pinning a MariaDB container image by digest, and updating two Markdown docs. The material contained no biology, chemistry, or medical content; it was YAML, composer.json/lock, psalm.xml, and Markdown. The flagged turn was reading the git diff.

Request ID: req_011CgxYwSWaekBXTiVsufURM
Message ID: msg_011CgxYwSjiz9h11zsBtecd9

Impact: The independent review step of our delivery workflow could not complete on Opus 5.5, so we had to fall back to a different model.

Environment Info

• Platform: darwin
• Terminal: xterm-256color
• Version: 2.1.322
• Feedback ID: 2f0f2e46-2bf4-480f-af1b-6d761aa2e8ad