On the contrary, subagents save context overall, when the task is sufficiently large.

Also, my experience is that Fable 5.1 is very good at prompting/orchestrating Opus/Sonnet subagents when working on a larger task (e.g. 1-2M context window use only for the orchestrator itself).

If you use subagents your main agent won't need to compact as often, with the loss of information that entails.