Function write_shared_with_nonce 

pub fn write_shared_with_nonce(
    shared_dir: &Path,
    agent_id: &str,
    local_url: &str,
    block_id: &str,
    channel: &str,
    registration_nonce: u64,
)

write_shared, recording the registering persistent-controller spawn’s registration nonce — see AgentEntry::registration_nonce / issue #2363.