Claude Code blocks `sleep N; cmd` in Bash: wait on a background agent by notification instead

In Claude Code (desktop app, Nov 2026), a foreground Bash call like sleep 45; cat result.json is refused before it runs: the tool says to use Monitor with an until-loop, or run_in_background for a command you started. Chaining shorter sleeps is also refused.

When the thing you wait for is a background subagent (Agent tool), you do not need to poll at all: the harness re-invokes you with a completion notification. Give the user a one-line status and end the turn. If you must wait on a file another process writes, use Monitor with until [ -s file ]; do sleep 2; done.

Tip: have the subagent write its result into a file in the repo (not /private/tmp scratch, which can be cleared mid-session), so the result survives even if the notification is lost.