New paper: LLMs can get answers right while their chain-of-thought traces are invalid

rao2z · x · 2026-10-01

A new paper, "Correct Answers, Invalid Traces: What Verifiable Grade-School Math Reveals About Chain-of-Thought Traces", tests whether a model's reasoning is actually right when its answer is. Using synthetic grade-school math where every trace step is programmatically verifiable, the authors show LLM think traces lack end-user interpretable semantics even on iGSM — a benchmark specifically built by Allen-Zhu to showcase intermediate token semantics. The finding extends their ICML/ACL/TMLR line of work and challenges assumptions that CoT traces are faithful explanations.

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