Support configured model defaults for skills

What variant of Codex are you using?

App, CLI

What feature would you like to see?

I usually keep a thread on a heavier model for normal coding and review, but some skills are a much better fit for lighter models.

Right now, if I want that split, I have to handle it manually:

1. Sometimes create a new thread to keep things clean
2. Switch the thread model to something lighter like gpt-5.4-mini or gpt-5.3-codex-spark
3. Invoke the skill
4. Switch the thread back to gpt-5.4 with high/xhigh reasoning for normal work

Sometimes I can also get the behavior I want by explicitly telling Codex to run the skill on a different model for that one turn. But that is still manual, easy to forget, and not something I want to restate every time.

Because of that friction, I also sometimes just run the skill on gpt-5.4 with high/xhigh anyway, which is not an efficient use of the heavier model.

What I want is a configuration mechanism for skill-level model defaults. I want to set it once, then have that skill automatically use the configured model when invoked, without changing the model for the whole thread.

After the skill finishes, the thread should continue on its original model.

Additional information

Any implementation is fine as long as it is persistent and automatic.

Possible shapes:

• skill metadata can declare a preferred model and reasoning effort
• config.toml can map skill name or path to a model
• some other per-skill default mechanism

The main thing is that this should be configuration, not just a one-off instruction in the prompt.