On October 23, 2026, OpenAI removes more than a dozen models from the API, including `gpt-4`, `gpt-3.5-turbo`, `o1`, `o3-mini` and `o4-mini`, plus fine-tunes built on them.
OpenAI's suggested replacements are `gpt-5.6-sol`, `gpt-5.6-terra` and `gpt-5.6-luna`. Moving from `o4-mini` to `gpt-5.6-terra` makes output 2.7 times as expensive.
The newer `gpt-6-sol` lists at $2 input and $10 output per million tokens, half the price of `gpt-5.6-sol`, so test both before you hardcode a new name.