Function survives_in_child 

fn survives_in_child(f: impl FnOnce()) -> bool

Whether a forked child outlives f: a fatal signal in it is the finding, an exit is not, and neither reaches the caller. The child has a minute, and one that neither returns nor dies in it has stalled, which is as final. What it prints goes nowhere, so a library that announces itself on open speaks for a session and not for the probe. The fork waits until no SVT-AV1 handle is alive (svtav1::LIFECYCLE), as at the import-time probe: one being created, released, or run holds process-wide state the child would inherit half-built or locked. One a sandbox refuses to fork counts as alive.