Running older models fails with Unknown model gpt-5.1 is used

What version of the IDE extension are you using?

26.422.30944

What subscription do you have?

API

Which IDE are you using?

VS Code

What platform is your computer?

macOS

What issue are you seeing?

I have a minimal /Users/cneilson/.codex/config.toml file that has

model = "gpt-5.1"

When opening the codex extention in VS Code, the Output logs show the error

message="codex_models_manager::model_info: Unknown model gpt-5.1 is used. This will use fallback model metadata."

I observe the same behaviour using the CLI

This used to work fine in March, but haven't touched it since then.

What steps can reproduce the bug?

Use a config file with

model = "gpt-5.1"

In it, then check output logs

### What is the expected behavior?

GPT 5.1 should be used

### Additional information

I am authenticated via an API key, not via ChatGPT