Function unlock_with_passkey 

pub fn unlock_with_passkey(
    server: &Server,
    device: &str,
    token: &str,
    response: &str,
    secret: &str,
) -> Result<Unlocked, Problem>

Logs in with a passkey and opens the vault with the key’s secret: token as passkey_ask gave it, response the key’s answer (JSON, as Bitwarden’s apps send it), secret the key’s PRF output (base64url). No second step: Bitwarden counts the key’s PIN as one.