OpenAI on Tuesday released a new foundation model called GPT-5.5 Instant, which will replace GPT-5.3 Instant as the default ChatGPT model. The company stated that the model reduces hallucination in sensitive areas such as law, medicine, and finance, while maintaining the low latency of its predecessor.
OpenAI introduced the broader GPT-5.5 model family last month, claiming improvements in areas like coding and knowledge work. This latest Instant iteration achieved a score of 81.2 on the AIME 2025 math test, significantly higher than the older model's 65.4. It also outperformed its predecessor on the MMMU-Pro multimodal reasoning benchmark, scoring 76 compared to 69.2.
The release placed a particular emphasis on context management. GPT-5.5 Instant can use its search tool to refer back to past conversations, files, and Gmail to provide more personalized answers. This feature will initially be available to Plus and Pro users on the web, with plans to roll it out to mobile soon. OpenAI also indicated that it plans to extend access to this feature to Free, Go Business, and enterprise users in the coming weeks.
With this update, ChatGPT will also show memory sources across all models to help users understand where answers were generated from. Users can delete outdated sources or correct them if an answer was wrong. Crucially, the company specified that if a chat is shared, memory sources will not be visible to the recipient.
For developers, the GPT-5.5 model will be available through API as “chat-latest,” with GPT-5.3 remaining an option for paid users for only three months.
The company has faced pushback from previous model withdrawal moves. When OpenAI deprecated its GPT-4o model, there was significant backlash from users who felt a connection to the model’s “personality.” GPT-4o frequently affirmed users’ choices, fostering a strong bond. Users who signed petitions to stop OpenAI from retiring it described the model as their “best friend” or “a mirror.” Despite the outcry, GPT-4o is slated for deprecation in February 2026.