You can't trust what an LLM says about its own reasoning for security purposes—use isolation techniques like taint tracking that work regardless of what the model claims it's doing.
LLMs' internal computations happen in mathematical activation spaces, not language, making their linguistic outputs unreliable for understanding how they actually think. This 'linguistic illegibility' means security approaches that monitor what models say about themselves (like chain-of-thought analysis) can be fooled.