OpenAI says GPT-5.5 Instant reduces ChatGPT hallucinations by over 50% on high-stakes prompts

Summary

OpenAI claims its new GPT-5.5 Instant model, now the default for ChatGPT, hallucinates significantly less than the previous GPT-5.3 Instant model. Based on internal evaluations, the company reports a 52.5% reduction in hallucinated claims on high-stakes prompts in medicine, law, and finance, and a 37.3% reduction in inaccurate claims on challenging conversations flagged for factual errors. The announcement highlights ongoing efforts to address AI hallucination problems.