until的问题

Until she spoke I hadn't realized she was foreign=I hadn't realized she was foreign until she spoke
the agent was not known until a doctor found it by chance
until后spoke 和found 都是过去时
the agent was not known 表状态可用过去时也可用过去完成时。the agent had not been known .

the agent was not known 这个代理籍籍无闻, 直至的意思
hadn't realized 是之前我没有发觉的意思

前一个until用在状态（not known）后 故用过去时
后一个用在动作（spoke）后 故用过去完成时

这两个句子里的时态跟UNTIL都没有直接关系的，until是“直到...才...”的意思，句子里面两个从句中的时态都与主句相关！