Claude's Fable 5.2 solved two open problems in theoretical physics related to black holes. In the first, Fable 5.2 completed a laborious calculation that had gone unsolved for 23 years. What Anthropic's new model just did in theoretical physics. In 1983 physicists showed black holes form in one sudden jump as these universes heat up, like water hitting a boil > that proof only worked for big universes. The check for tiny ones was planned in 2003 and called "too laborious to complete" Fable 5.2 finished it, "working largely autonomously." the jump happens there too. It also found the exact limit of a quantum gravity test physicists have used for 15+ years. Opus 5.5 got the same answer on that one, independently a 2003 plan. a 2026 finish. both results are preprints. peer review comes next.