Hi everyone,
I am a subscriber of the ChatGPT Pro 5x tier.

Since the release of version 5.6, I haven’t had the chance to use the Pro tier model. I can use the Thinking model normally, but the Pro model will be automatically routed down to the 5.5-mini model:

In the HAR network log, it can be seen that my subscription level information and requests are all normal, but the returned model is a downgrade model:
“plan_type”:“prolite”

“model_slug”:“gpt-5-6-pro”,“default_model_slug”:“gpt-5-6-pro”,“thinking_effort”:“standard”

“resolved_model_slug”:“gpt-5-5-mini”

Therefore, I am quite certain that there must be an abnormal issue with my account on the server side. I have sent a screen recording and the har log file from the operation at the same time to the help center to reproduce the error phenomenon. However, I have not received any feedback from the human experts yet, and the Codex quota is not as durable as before. I am not sure about the differences between my current account and the Plus subscription. I wonder if others have the same problem as me.

The case number I have received is 11851745.

I hope my account issue can be resolved and replied to. At least, I would like to know the current handling progress instead of waiting indefinitely.

same as you. I even didn’t use pro model, just use “medium” level and it said that “5.5 mini”, not 5.6 thinking days before.