GPT-5.5 Instant Mini rollout in ChatGPT as new fallback model

OpenAI is rolling out GPT-5.5 Instant Mini in ChatGPT, according to the company's ChatGPT Release Notes updated July 6, 2026. The new model replaces GPT-5.3 Instant Mini as the fallback that users reach after hitting rate limits for GPT-5.5 Instant or Auto. It will not appear in the model picker. The update does not affect the API or Codex. Compared with the prior fallback, GPT-5.5 Instant Mini better tracks evolving user intent, calibrates tone, and avoids repetitive or overly structured responses. Testing showed stronger personalization and fewer factual issues. The change is described in the official release notes section dated July 6, 2026.