The Letters on the High Priest's Garment Are What Provided the Answer?

There is some evidence in later jewish sources, meaning sources like the first century historian josephus and the even later rabbis who wrote the mishna and the ta. Josephus says that the stones on the high priest's garment would glow with light in ways that would signify god's will. But there are three problems with that. He doesn't connect that explicitly with the uriman thamim. And third, he says this stopped happening two red years before his time because god was unhappy with the people. So it could just be a legend he heard.