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

THE DECODER / 5/6/2026

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Key Points

  • OpenAI is changing ChatGPT’s default model to GPT-5.5 Instant, with a focus on reducing errors in sensitive areas.
  • Internal tests reportedly showed a 52.5% reduction in hallucinated claims on high-risk topics such as medicine and law.
  • A new feature, “memory sources,” will let users see which stored context contributed to a specific response.
  • Rollout is immediate for all users, while enhanced personalization based on past chats, files, and Gmail starts first for Plus and Pro users on the web.

OpenAI is swapping out ChatGPT's default model for GPT-5.5 Instant. In internal testing, the update produced 52.5 percent fewer hallucinated claims on high-risk topics like medicine and law. A new feature called "memory sources" lets users see which stored context shaped a given response. The model is rolling out to all ChatGPT users right away, though personalization based on past chats, files, and Gmail launches first for Plus and Pro users on the web.

The article ChatGPT update rolls out GPT-5.5 Instant with fewer hallucinations and more personalized answers appeared first on The Decoder.