OpenAI’s GPT-5.5 Instant brings big gains in factual accuracy
OpenAI has rolled out GPT-5.5 Instant as the new default for ChatGPT, touting substantial reductions in hallucinations across a range of high-stakes topics. According to OpenAI’s internal evaluations, the model produced 52.5% fewer hallucinated claims on prompts covering areas such as medicine, law, and finance compared with its GPT-5.3 Instant predecessor.
The company also reports a 37.3% decline in inaccurate claims on especially challenging conversations that users had previously flagged for factual errors. Those improvements suggest the model is better at grounding responses and avoiding confidently stated mistakes — a key milestone for everyday reliability and user trust.
Why this matters: fewer hallucinations mean safer guidance and more dependable assistance for millions who rely on ChatGPT for research, professional queries, and decision support. Reductions on high-stakes topics are particularly encouraging because incorrect claims in those domains can have outsized consequences.
OpenAI’s figures come from internal testing, so independent assessments and real-world usage will help confirm the full scope of improvements. Still, making the model with stronger factuality the default for ChatGPT signals tangible progress toward AI that better supports users when accuracy matters most.
- Default upgrade: GPT-5.5 Instant replaces the prior default in ChatGPT.
- High-stakes win: 52.5% fewer hallucinations on critical prompts.
- Flagged conversations: 37.3% fewer inaccurate claims on user-flagged exchanges.