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Beyond the Commitment Boundary: Probing Epiphenomenal Chain-of-Thought in Large Reasoning Models

paperactiveprovisionalbeyond-the-commitment-boundary-probing-epiphenomenal-chain-of-thought-in-large-reasoning-models-1b14c438·1 events·first seen 5d ago

Aliases: Beyond the Commitment Boundary: Probing Epiphenomenal Chain-of-Thought in Large Reasoning Models

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7arXiv · cs.CL·5d ago·source ↗

Research identifies 'commitment boundary' in chain-of-thought reasoning, enabling 55% CoT length reduction

A new arXiv preprint introduces the concept of a 'commitment boundary' in chain-of-thought reasoning — a sharp transition point where a model's answer stabilizes, after which subsequent reasoning steps are 'epiphenomenal' and causally inert. The authors use early-exit probing and attention probes to detect this boundary, finding it can be linearly decoded from intermediate steps and generalizes across tasks. Exploiting this signal to exit reasoning blocks at the commitment boundary reduces CoT length by up to 55% on average with negligible performance loss, with direct implications for inference efficiency in large reasoning models.