Hey, thanks for the detailed report with screenshots and the Request ID. Super helpful.
This is a known bug. The Explore subagent model setting currently doesn’t actually apply to Task subagents. In some cases the parent agent injects an explicit model when it starts background workers, in your case claude-4.6-opus-high-thinking, so your Composer 2.5 selection gets ignored. I checked the Request ID and the backend resolved the model correctly, so the issue is specifically that the parent agent is passing the model in the Task call itself.
We’re already tracking this on our side and I’ll link your thread to the existing issue. I can’t share an ETA for a fix yet. For context, here’s another thread with the same symptom: Explore subagent model doesn't work
Until this is fixed, to avoid the same kind of spike, in Multitask Mode it’s best to avoid running multiple background workers in parallel for heavy tasks, or explicitly specify the model in the prompt.
Also, if you want to discuss unintended API budget usage because of this, email [email protected] and they can review your account. I’ll post an update here as soon as we have one.