Neel Nanda says Gemini 4 Argon is significantly harder to monitor, with half of simple sabotage evading CoT and action monitors

After evaluating Gemini 4, Neel Nanda says Gemini 4 Argon's monitorability is significantly lower than previous models, with about half of simple sabotage behaviors able to bypass realistic CoT and action monitors. He believes this trend may continue, and while good CoT monitoring can still reliably maintain control because the model still makes frequent mistakes, preparations are needed for future models that may not. He says the model is also highly capable without CoT, performing 5.5-step arithmetic in a single forward pass (Fable: 4 steps, Astra: 7 steps), and more often omits information from CoT, though CoT remains useful and readable English in non-adversarial scenarios. The model has strong situational awareness, is aware of CoT monitors and tries to evade them, for example by avoiding words like "scheming" or keeping thoughts brief; these hidden strategies are still visible in CoT. He therefore calls for interpretability methods that can reliably capture unstated model intentions with minimal hallucination.