ChatGPT update rolls out GPT-5.5 Instant with fewer hallucinations and more personalized answers

OpenAI is swapping out ChatGPT's default model for GPT-5.5 Instant. The update reduces hallucinations and tightens responses, while a new feature called "memory sources" shows users which stored context shaped a given reply.

GPT-5.5 Instant replaces GPT-5.3 Instant and is also available through the API as "chat-latest." In OpenAI's internal testing, GPT-5.5 Instant produced 52.5 percent fewer hallucinated claims than its predecessor on high-risk prompts in medicine, law, and finance. On tough conversations users had previously flagged for factual errors, inaccurate claims dropped by 37.3 percent, OpenAI claims.

OpenAI offers an algebra problem as an example. A user uploaded a photo of a handwritten equation with a calculation mistake. GPT-5.3 Instant initially agreed with the solution, then noticed that x=3 didn't work but wrongly concluded there was no real solution. GPT-5.5 Instant also agreed with the user's math at first, but then caught the error in how the user had rearranged the equation and solved the corrected quadratic.

Benchmark scores tell a similar story. On AIME 2025, a competitive math exam, accuracy jumped from 65.4 to 81.2 percent. GPQA, which tests PhD-level science reasoning, climbed from 78.5 to 85.6 percent. CharXiv, a benchmark for interpreting and reasoning about scientific charts, went from 75.0 to 81.6 percent.

MMMU-Pro, which measures how well models handle expert-level questions across text and images, rose from 69.2 to 76.0 percent. The error rate on OmniDocBench, a test for extracting structured data from complex documents, dropped from 14.6 to 12.5 percent.

Tighter answers and smarter personalization

OpenAI also focused on cutting fluff. Answers are shorter without losing substance; the model asks fewer unnecessary follow-ups, drops superfluous emojis, and skips heavy formatting, the company says. "It can deliver the same information, often with more utility than previous models, while reducing the verbosity and overformatting that can make responses too long", OpenAI writes.

The model also makes better use of context from past chats, uploaded files, and connected Gmail accounts when those features are turned on. GPT-5.5 Instant is reportedly better at judging when extra personalization actually helps a response, and it searches previous conversations faster.

OpenAI is also rolling out memory sources across all ChatGPT models. When a reply draws on stored context, users can now see which information was used, whether that's a saved note or a past chat. Entries can be flagged as relevant or irrelevant, edited, or deleted.

But memory sources won't always show every factor behind a response, OpenAI says. Only some chats the model searches will appear as sources, for instance. The company plans to make the view more complete over time. Memory sources aren't passed along when a chat is shared, and temporary chats neither read from nor update memory.

Staggered rollout across plans

OpenAI says GPT-5.5 Instant is rolling out to all ChatGPT users right away. Paying users can still access GPT-5.3 Instant through model settings for another three months before it's retired.

Enhanced personalization based on past chats, files, and Gmail is launching first for Plus and Pro users on the web, with mobile coming soon. Free, Go, Business, and Enterprise plans are expected to get access over the coming weeks. Memory sources will roll out to all consumer plans on the web first, with mobile to follow. Some personalization features may not be available in every region.

OpenAI recently introduced GPT-5.5 Thinking as the higher-tier model, while GPT-5.5 Instant serves as ChatGPT's everyday default. The Thinking version is still more powerful: on cybersecurity tasks it reportedly matches Claude Mythos, and it replaces the specialized Codex coding models.