How long it has been since the last release against the line's usual gap and its recent ones — the rhythm, not a date.
Newest first — what each version changed versus the one before, in OpenAI's own numbers.
OpenAI's new lightweight model: far fewer made-up answers and much stronger math than GPT-5.3 Instant Mini — and it's now the default free model in ChatGPT.
Compared with GPT-5.3 Instant Mini · the model it replaces
Makes up about half as many wrong answers on tricky questions
High-stakes prompts — questions where a wrong answer really matters
52% fewer
▲ vs GPT-5.3 Instant Mini · same tests
Solves 8 in 10 competition-level math problems
AIME 2025 — a hard high-school math competition
81.2
▲ up from 65.4 · +16 points
Now the model free ChatGPT users get by default
Availability — which users get this model without paying
default free ChatGPT
✦ new in GPT-5.5 Instant
One email a week: what AI models shipped, the actual differences vs the previous version, and what's coming next. No filler.