Abstract
Current large language models often suffer from subtle, hard-to-detect reasoning errors in their intermediate chain-of-thought (CoT) steps. These errors include logical inconsistencies, factual hallucinations, and arithmetic mistakes, which compromise trust and reliability. While previous research focuses on mechanistic interpretability for best output, understanding and categorizing internal reasoning errors remains challenging. We describe a methodology to uncover structured representations of reasoning errors in CoT prompting using Sparse Autoencoders, evaluating SAE activations within neural networks to investigate how specific neurons contribute to different types of errors.