I tested OpenAI’s three claims about GPT-5.5 Instant, and only one fully held up

OpenAI rolled out GPT-5.5 Instant as ChatGPT’s default model, pitching it as more accurate, more concise, and more personalized.

In a hands-on comparison with GPT-5.2, GPT-5.5 was generally more accurate and more conversational, with fewer hallucinations.

However, GPT-5.5 often produced longer answers, so its promised concision was not consistent in practice.

Personalization testing was mentioned, but the provided review did not fully detail those results.