[Bug] False positive "reasoning_extraction" safeguard flag blocks all turns in benign session

Bug Description
Subject: False positive "reasoning_extraction" flag blocking every turn in a benign robotics-simulation session (Claude Code, Opus 5.5) What happened: Claude Code with Opus 5.5 started returning "Opus 5.5's safeguards flagged this message" with Details: [reasoning_extraction] on every turn, from about 9:39 AM to 9:43 AM (UTC-6) on 2026-10-09. The session was working normally before that. Content of the session (benign): I'm running physics simulations and model-predictive control (MPC) demos for a bimanual robot arm project (OpenArm): tipping a can upright, folding a towel, and a catching-a-falling-can design. The flagged turns were only status updates and notes: - background monitor events printing simulation time, can tilt angle, grasp/pivot phase, and fold error - reading/editing a disclosure memo (notes/demo2_disclosure_ja.md) - reading demo1_mpc.py and demo_lib.py I was not asking the model to reveal or reproduce its reasoning. There is nothing in the content that I can see as policy-relevant. Impact: - The flag repeated on every retry, including a trivial message ("a? どうした" = "huh, what happened?"), so the session is effectively dead on Opus 5.5. - A long-running simulation (about 1285 s of wall time) and its follow-up report task were still running in the background, so I could not get the model to read the results or continue the workflow. - I had to switch models / start a new session to continue. Request IDs: - req_011CfrvDYLixVDpBgoaDWnBg (msg_011CfrvDYe5tPVMeHwusZhB2) - req_011CfrvJfWxiVQzGb6frZumt (msg_011CfrvJg4DKLF6PbUNEPG75) - req_011CfrvLJhsyWxxvU16wNkTc (msg_011CfrvLK3DyxzecT2JTojLu) Request: Please review whether this classifier flagged the session incorrectly. Also, if possible, a flag that triggers on routine monitor/tool-output turns should not keep blocking all subsequent turns of the session.

Environment Info

• Platform: darwin
• Terminal: iTerm.app
• Version: 2.1.295
• Feedback ID: d107f977-076f-47ed-947c-eafc14c92368