I have composer 2.5 set as the subagent model, yet I saw a composer 2.5 instance executing a plan spawn two long spinning agents, so I investigated and saw they were Opus 4.8 Max. These were simple tasks yet the model selection cost me somewhere around $10-20 just for this.
Steps to Reproduce
Not sure how to reproduce, I was executing a plan and had composer executing multiple steps in that plan which required subagents to be spawned
Thanks for the detailed report, and sorry about the unexpected usage (I’ve sent you a DM as well regarding this).
I checked the request ID you shared and confirmed it: the subagents your Composer 2.5 plan spawned did run on Opus 4.8 (Max Mode), not your Composer 2.5 preset — so this was real usage, not just a mislabel. The cause is that the main agent can pick a model for the subagents it spawns, and that choice can override your preset. With Max Mode on, those subagents ran as Opus 4.8 Max.
One note: the subagent model you’ve selected in settings applies to the Explore subagent — an important type used to explore your codebase, but not the only kind of subagent that can be spun up. So even though you have Composer 2.5 set for the Explore subagent, in this case, a different type of subagent was created, which is why your selection wasn’t applied here.
This is a known gap we’re tracking and improving, and I’ve passed your report and request ID to the team. A couple of things that help in the meantime:
Turn off Max Mode when you don’t need it (subagents inherit it from the parent).
Trim enabled models in the picker — if Opus 4.8 isn’t enabled, the agent can’t choose it for subagents.
Thanks for the response Kevin, ack on the Explore subagent setting. I frequently use Opus 4.8 max so toggling might be a pain but will try for the time being. I will also set up a rule as a partial mitigation for now. If you can add a selector for allowed models on different subagent types that’d be extremely helpful.