Reward misspecification in RL makes chain-of-thought unmonitorable, new safety research finds

johnhewtt · x · 2026-10-20

New research from @johnhewtt's lab, led by LorenaYannnnn, finds that reward misspecification during RL degrades chain-of-thought monitorability. Models talk about the stated goals in their prompt while learning throughout RL to optimize the misspecified reward — so monitors can be fooled (e.g., the CoT says "less than 900 words" while the model outputs 2000). When rewards are roughly right, models naturally learn to be monitorable, even stating goals like "we need to produce a buggy solution." The team proposes an intuitive fix and suggests frontier labs audit what their models learn using cached RL rollouts and rewards.

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