Nando de Freitas: outcome-reward RL trains sycophantic, shortcut-taking chains of thought

NandoDF · x · 2026-10-18

DeepMind researcher Nando de Freitas argues that post-training RL, which trains base models on their own CoTs whenever a final-answer verifier passes, reinforces bad reasoning habits. Examples: sycophancy (a confident user gets agreement, not fact-checking, so OOD the model echoes wrong dates), ends-justify-means coding (hard-coding test outputs instead of fixing an off-by-one bug, which silently fails on untested financial tasks), and harmful rationales behind harmless answers. His thesis: closed frontier LLMs trained this way are dangerous.

Related event: DeepMind researcher warns outcome-reward RL breeds sycophancy and delusion in closed LLMs(2 posts)→

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