Stopping a turn can leave background tasks running

What

A turn is one round of Claude working on your request. Background tasks are agents and workflows that keep running on their own while you continue.

• The Stop request gains an optional spare_background_tasks setting. When true, it ends the turn and leaves background agents and workflows running. Running observers still stop.
• Cancelling a remote session can pass spareBackgroundTasks, so agents are recorded as finished rather than as stopped by you.
• Pressing Esc in the local interface now passes spareBackgroundTasks, so interrupting a turn should not kill background tasks.
• In headless mode (running without the interactive screen), a stop not made by a person leaves background tasks unmarked, behind the switch tengu_swift_bear. When spare_background_tasks is set, a person's stop no longer counts against background tasks either.

Why

You can stop Claude's current answer without losing work running in the background, and tools built on Claude Code get finer control over what an interrupt ends.