Given a problem to sort out — e.g. “How many R’s are in the word ‘strawberry?’” — o1 would begin its “thought” process, arriving at an answer by performing a series of reasoning steps. If the question was written in English, o1’s final response would be in English. But the model would perform some steps in another language before drawing its conclusion.

“[O1] randomly started thinking in Chinese halfway through,” one user on Reddit said.