OpenAI Codex and Kimi K3 solve 10-year-old open mathematical optimization problem

AI reasoning models settle decade-old problem in optimisation theory

On 14 August 2026, researchers Kenan Xu and Xiangfeng Wang published a paper on arXiv (arXiv:2608.14396) demonstrating how frontier artificial intelligence reasoning models resolved a ten-year-old open problem in mathematical optimisation theory. The study detailed how OpenAI Codex, driven by GPT-5.6 Sol, alongside Moonshot AI Kimi Code, powered by Kimi K3, successfully disproved a long-standing conjecture regarding the convergence of the three-block Alternating Direction Method of Multipliers, commonly known as ADMM. Operating under the guidance of human researchers, these advanced reasoning engines constructed formal algebraic counterexamples that proved direct three-block ADMM can fail to converge even under conditions previously believed to guarantee stability.

Why the result matters

ADMM is a widely used algorithm for solving large-scale optimisation problems, with applications across machine learning, signal processing and distributed computing. While the two-block version of the method has well-established convergence guarantees, the behaviour of the three-block extension had remained an open question for a decade. The counterexamples produced in the study close that gap, showing that the conjectured convergence conditions do not hold in general.

OpenAI Codex and Kimi K3 solve 10-year-old open mathematical optimization problem
Image source: AI-generated supporting image

Human-guided AI at work

According to the paper, the human researchers set the problem framing and verified each candidate counterexample, while the reasoning models carried out the algebraic construction and iterative refinement. The authors describe the workflow as a collaboration in which the models proposed candidate structures and the researchers checked them against formal criteria, with every result independently verified before publication. The finding adds to a growing list of open mathematical questions resolved with the assistance of AI reasoning systems.

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Published: 18 Aug 2026

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