Claude Fable 5.2 cracked a black-hole calculation that physicists had left unfinished for 23 years.
A physicist has already checked the work, i.e. this is new knowledge in fundamental physics that came largely from an AI.
In 1983, Stephen Hawking and Don Page showed that when a certain kind of universe heats up, a black hole forms suddenly, like water hitting boiling point, but their method only worked for large universes.
In 2003, physicists laid out the calculation needed for tiny universes, but it was so long and tedious that nobody finished it, until Claude did it largely on its own and found that black holes form suddenly there too.