Function egress 

pub fn egress(
    spans: &[SecretSpan],
    target: &EgressTarget,
    prior_public_egress: bool,
) -> EgressOutcome

The Egress door: secret shapes never leave (C13), and the first public egress of a run is named. The subject counts spans and offsets — the matched bytes never appear (the error message is itself an egress surface).