Import AI #453: MirrorCode Benchmark Shows Claude Opus 4.6 Can Autonomously Reimplement 16,000-Line Codebases

Import AI (Jack Clark)·high signal

METR and Epoch AI's MirrorCode benchmark tests whether AI models can autonomously reimplement complex software. Claude Opus 4.6 successfully reimplemented 'gotree', a 16,000-line bioinformatics toolkit — a task that would take a human engineer weeks. Jack Clark also covers Ryan Greenblatt doubling his probability estimate of full AI R&D automation by end of 2028 from 15% to 30%.