Intern-S2 helps prove 3D Ghys conjecture, checked in Lean
Shanghai AI Laboratory said on October 15 that Xu Disheng, a visiting scholar there and professor at Greater Bay Area University, used its Intern-S2 science multimodal model in a human-machine collaboration to prove the three-dimensional Ghys conjecture, a problem open for more than 30 years. A Peking University team led by Dong Bin and Liu Ruochuan formalized all four main theorems with its own SHEAF framework and checked them in Lean, taking about five days with up to 100 agents in parallel and roughly 550,000 lines of Lean code. The lab says Intern-S2 ran seven successive rounds of reasoning, expanding its problem graph from 15 to 389 nodes and producing a 400-page first-round derivation report before the final thousand-plus pages; the paper is on arXiv and the formalization code on GitHub. The lab also claims the model leads existing open models on IMO-Proof and AdvancedMathBench and beats Gemini 3.1 Pro on some metrics, and notes an expert had tried the problem with GPT-6 without finding a proof.
It is a concrete case of a Chinese model contributing to a research-level proof that was then machine-verified, offering a reusable pipeline of model search, expert judgement and formal checking.