You'll notice
Guidance text now suggests fewer concurrent subagents for medium-sized tasks, 10 instead of 15
What
The guidance text shown for how many subagents to run concurrently ('aim for <N> agents') has been lowered for the medium size tier, from 15 down to 10. The small tier (5) and large tier (50) are unchanged.
Why
This adjusts the recommended concurrency for medium-scale multi-agent tasks, presumably to better match what works well in practice at that scale.