GPT-6 Pro disappeared?

A user on ChatGPT Pro reported that the GPT-6 Pro option, previously available, has disappeared, with GPT-5.6 with Very High thinking now being the highest selectable option. They are unsure if OpenAI removed it, is testing something, or if it's a bug, and are asking if other Pro users are experiencing the same issue.

This report is the first to note the disappearance of GPT-6 Pro from ChatGPT Pro, unlike earlier discussions focusing on its potential release.