OpenAI used its new large language model GPT-5.6 Sol to solve the "cycle double cover conjecture," a math problem humans have struggled with for more than a half-century. The company timed the proof to the model’s full public release last Friday. The conjecture, about graphs, was guessed in the 1970s by several mathematicians. The AI-generated proof shows that any guess-applicable graph can be doubly covered with no more than eight well-chosen loops, excluding graphs with big sections connected by a single edge. Noga Alon, a mathematician at Princeton University, called the breakthrough "yet another impressive example demonstrating that AI tools will change—and are already changing—mathematical research significantly." Andrew Sutherland, a mathematician at the Massachusetts Institute of Technology, said, "My guess is we will keep seeing examples of this—supposedly 'hard' problems having 'easy' solutions found by LLMs."