GPT-5.4 Mini Begins Rollout to Free and Go ChatGPT Users as Thinking Feature and Rate-Limit Fallback

OpenAI Release Notes·medium signal

OpenAI began rolling out GPT-5.4 Mini to ChatGPT Free and Go tier users, available as the Thinking feature entry point and as an automatic rate-limit fallback for paid plans during high load. Enterprise customers retain Auto routing. The launch completes the GPT-5.4 family tiering — Thinking (paid) and Mini (free/go) — following the original GPT-5.4 Thinking release in early March.