Constant DEFERRED_ORPHAN_GRACE_TICKS 

pub(super) const DEFERRED_ORPHAN_GRACE_TICKS: u32 = 20;

Consecutive watchdog ticks with no process and no spawn in flight before the queue is declared stranded and reported (spec §4.5). Long enough to ride out the gap between a process exit and the respawn that follows it (a stale---resume retry, a fallback respawn); short enough that a dead agent’s backlog is surfaced rather than held forever.