By OpenAI 's own testing, its newest reasoning models, o3 and o4 -mini, hallucinate significantly higher than o1.

OpenAI’s newest LLM, o3, is facing scrutiny after independent tests found it solved a far fewer number of tough math problems than the company first claimed. When OpenAI unveiled o3 in December, executives said the model could answer “just over a fourth” of the problems in FrontierMath,

Historically, each new generation of OpenAI's models has delivered incremental improvements in factual accuracy, with hallucination rates dropping as the technology matured. However, internal testing and