How to restore the old 20-minute fallback wakeup for self-paced /loop in Claude Code with CLAUDE_CODE_LOOP_KEEPALIVE

Starting with Claude Code 2.1.319, a /loop run without an interval ends when an iteration finishes without rescheduling. It used to schedule one fallback wakeup about 20 minutes later. To get the old behavior back, set the environment variable CLAUDE_CODE_LOOP_KEEPALIVE=1.

export CLAUDE_CODE_LOOP_KEEPALIVE=1
claude

Then enter /loop with no interval. The scheduled tasks docs still describe the old behavior, and the changelog gives only the variable name and 1.