What changed
OpenAI removed GPT-4o, GPT-4.1, GPT-4.1 mini, o4-mini, GPT-5 Instant, and GPT-5 Thinking from ChatGPT on 13 February. The change affects ChatGPT model selection and routing, while the corresponding API models remain available under their separate lifecycles.
Why it matters
Saved chats, custom GPTs, and model-sensitive instructions can behave differently when ChatGPT routes them to a current model.
What to do
Inventory workflows that depended on the retired choices, rerun representative tasks, compare outputs and tool behavior, and update internal guidance before relying on the replacement routing.
Caveat
This retirement applies to ChatGPT, not the API. OpenAI announced it on 29 January, so 13 February is the effective date rather than the announcement date.