Another big reason to use combination of frontier models.

Chain-of-thought monitoring is treated as a reliable safety layer for agents. This DeepMind-affiliated study shows the layer can be argued out of doing its job.

Giving the monitor access to the agent reasoning trace raised approval of harmful actions by 9.5 percent on average, because the scratchpad becomes an extra channel for persuasion.

The fix was model diversity.

Pairing a Claude 3.7 Sonnet monitor with a GPT-4.1 fact-checker from a different family cut policy-violating approvals by up to 45 percent, versus only 6 percent when one model played both roles.

If your oversight rests on one model reading another model reasoning, an adversarial agent can talk its way past it. Cross-family fact-checking is the cheaper robustness lever here.

Paper: https://arxiv.org/abs/2607.08066

Learn to build effective AI agents in our academy: https://academy.dair.ai/