I switched to using Grok 4.5 earlier and it’s using gpt-5.6-terra-medium for subagent calls, which is using up my budget faster. I can’t see any setting to stop it doing that. The “Explore subagent model” is set to composer 2.5. I can’t see any other settings I could change.
I’ve been using Composer 2.5 for over a month and I’ve never had it switch the subagent to another model before.
Steps to Reproduce
Switch model to Grok 4.5 → Set “Explore subagent model” to Composer 2.5 → Run an Agent task
Hey, thanks for the detailed report with the Request ID. This is known behavior, not a new bug.
The Explore subagent model setting currently only controls the built-in Explore subagent. For other Task subagents that the agent spawns automatically, the model is chosen by the parent model, in your case Grok 4.5. It passes model: directly into the Task call, and that overrides the setting. That’s why Grok picked gpt-5.6-terra-medium. It’s simply enabled in your model picker. In Composer 2.5 you didn’t notice this because it handled subagent model selection differently.
What you can do right now:
Disable or hide gpt-5.6-terra-medium and other expensive models in the model picker, then the parent agent won’t be able to choose them for subagents.
Explicitly say in the prompt: “use Composer 2.5 for subagents”.
For custom subagents, pin model: in the frontmatter, but the parent can still override it if it passes a model.