Activation patching says 76.9% of Qwen3-4B's stated reasoning steps are load-bearing, 11.4 points below what text-edit tests claim.

Patching the residual stream at each stated intermediate step with activations from a counterfactual run, on 2-6 hop lookup tasks. The standard behavioral text-editing test reports 88.2% on the same items (arXiv). Qwen3-1.7B drops to 54.8%. CoT monitoring on small models rests on weaker ground than the behavioral metrics suggest, and the behavioral metrics are what most monitoring systems use.