split-task

Split a task across sub-agents only when it saves cost or keeps the main session
free. Spawn per sub-agents.

When to split

Split automatically when the task will change 5+ files (excluding documentation)
and divides into independent parts that each need substantial reading or editing
on their own: multi-file migrations, broad audits, repetitive edits. Give each part
non-overlapping file ownership.

Run inline when the parts share most of their context, or the task is small or
sequential. Each spawned agent re-pays the shared context, so splitting a
medium-sized task costs more than doing it inline.