Think:
Sub-agent models allowed for this session
☑ GPT 5.5 Low
☑ GPT 5.5 Medium
☐ GPT 5.5 High
☐ GPT 5.6 Sol Ultra
Default: GPT 5.5 Medium
Routing: Agent chooses among approved options
☑ Ask before using anything unapproved
☑ Show model and effort on every sub-agent