Introducing GPT-5.4 mini and nano¹. OpenAI finally refreshed its smaller and cheaper models. The previous mini/nano release was GPT-5 in August 2025, while GPT-5.1-Codex-Mini in November 2025 was a more coding-specific branch.

It feels like OpenAI is gradually tidying up its model lineup. At least in the GPT-5.4 family, there is no separate “Codex”-suffixed specialized model, and the mini and nano variants seem to be catching up too.

I checked the Codex app this morning and saw that its built-in subagents are already using GPT-5.4 Mini.

Subagents using GPT-5.4 Mini