Constant SHUTDOWN_FLUSH_TIMEOUT 

pub const SHUTDOWN_FLUSH_TIMEOUT: Duration;

How long the host waits after forwarding core.shutdown to agentd before triggering its own VMM exit fallback.

agentd uses this window to sync() block-backed root filesystems and power off the kernel cleanly (or run its handoff sequence — see HANDOFF_POWEROFF_TIMEOUT). On a healthy guest the VMM exits well inside the window and the host fallback is a no-op; the fallback only fires when the guest is wedged.

Must exceed HANDOFF_POWEROFF_TIMEOUT plus margin for the init’s own signal handling — enforced at compile time below.