We began rolling that update back on April 28th, and users now have access to an earlier version of GPT‑4o with more balanced responses. Earlier this week, we shared initial details about this issue⁠—why it was a miss, and what we intend to do about it.

We didn’t catch this before launch, and we want to explain why, what we’ve learned, and what we’ll improve. We're also sharing more technical detail on how we train, review, and deploy model updates to help people understand how ChatGPT gets upgraded and what drives our decisions.

We’re continuously working to develop improvements on the models in ChatGPT, which we call mainline updates. Since launching GPT‑4o in ChatGPT last May, we’ve released five major updates⁠(opens in a new window) focused on changes to personality and helpfulness. Each update involves new post-training, and often many minor adjustments to the model training process are independently tested and then combined into a single updated model which is then evaluated for launch.

To post-train models, we take a pre-trained base model, do supervised fine-tuning on a broad set of ideal responses written by humans or existing models, and then run reinforcement learning with reward signals from a variety of sources.