I gave it a question I've been trying to answer for a long time: "What star designation system does Joseph Needham use in Science & Civilization in China? What star is referred to by the designation '4339 Camelopardi' in that book"?
Fable blew me away with its detailed answer[0] showing a chain of references going from J. E. Bode's 1801 catalogue Allgemeine Beschreibung und Nachweisung der Gestirne to Gustave Schlegel's 1875 work Uranographie Chinoise. I was excited, until I checked scanned copies of the cited books and did not actually find any star with the designation "4339 Camelopardi".
Upon following up with Claude, I was forced to downgrade to Opus, which admitted that Fable's answer was likely a hallucination. Ah, well!
[0]: https://claude.ai/share/0252a3f6-3d29-4de8-a893-010181d8b4e7
> I was forced to downgrade to Opus,
So you were forced to downgrade to opus because you dared to challenge the output of fable?
I had thought it said something about token usage, but I just clicked on "Switched to Opus 4.8 - Why?" and it says:
> Fable 5 has safety measures that flag messages on most cybersecurity or biology topics. They may flag safe, normal content as well. These measures let us bring you Mythos-level capability in other areas sooner, and we're working to refine them. Send feedback or learn more.
Perhaps Mythos realizes the true danger in studying Chinese Archaeoastronomy that we mere mortals fail to recognize!