OpenAI GPT-5.5 Instant (May 2026): new ChatGPT default model + API `chat-latest`
OpenAI says GPT-5.5 Instant is rolling out as ChatGPT’s new default model with improved factuality, tighter responses, and new memory-source transparency controls; it’s also available in the API as `chat-latest`.
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OpenAI says GPT‑5.5 Instant is rolling out as ChatGPT’s new default model (replacing GPT‑5.3 Instant) and is also available in the API as chat-latest. (https://openai.com/index/gpt-5-5-instant/)
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What OpenAI says shipped
According to OpenAI’s release post, the GPT‑5.5 Instant update focuses on:
- Smarter, more accurate answers with clearer, more concise responses. (gpt-5-5-instant/">https://openai.com/index/gpt-5-5-instant/)
- Improved factuality — OpenAI reports internal evals showing 52.5% fewer hallucinated claims vs GPT‑5.3 Instant on “high-stakes prompts” (medicine, law, finance), and 37.3% fewer inaccurate claims on conversations users flagged for factual errors. (gpt-5-5-instant/">https://openai.com/index/gpt-5-5-instant/)
- Less verbosity / overformatting and fewer unnecessary follow-up questions. (https://openai.com/index/gpt-5-5-instant/)
- Better handling of image/photo uploads, STEM questions, and deciding when to use web search. (https://openai.com/index/gpt-5-5-instant/)
New transparency controls: “memory sources”
OpenAI also says it’s introducing memory sources across ChatGPT models, which show what context was used when a response is personalized (for example, saved memories or past chats) and let you delete or correct that context. (https://openai.com/index/gpt-5-5-instant/)
Availability / rollout
OpenAI’s post includes these rollout notes:
- ChatGPT: GPT‑5.5 Instant is rolling out “starting today” to all ChatGPT users as the default model. (https://openai.com/index/gpt-5-5-instant/)
- API: OpenAI says GPT‑5.5 Instant is available in the API as
chat-latest. (https://openai.com/index/gpt-5-5-instant/) - Paid users: GPT‑5.3 Instant remains available for three months via model configuration settings before being retired. (https://openai.com/index/gpt-5-5-instant/)
Sources
- OpenAI: GPT‑5.5 Instant (May 2026): https://openai.com/index/gpt-5-5-instant/
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