The Structured Concurrency Model

Structured concurrency (JEP 453, preview) treats a group of related concurrent tasks as a single unit of work.

If the parent task splits into subtasks, those subtasks must all complete before the parent moves on, much like a block scope in ordinary code.

With raw executors, a spawned task can outlive its creator, leak, or be forgotten. Errors in one branch may go unnoticed while others keep running.

This leads to thread leaks, orphaned work, and confusing failure handling.