Epoch AI and METR's new MirrorCode benchmark found the top AI model correctly rebuilt real software from behavior alone in 56% of cases, up from about 30% for leading models roughly eight months earlier
Epoch AI and METR introduced MirrorCode, a benchmark for long-horizon coding tasks where AI agents must replicate the functionality of existing software without access to its source code. The AI solutions are evaluated by matching the original program's output on end-to-end tests. The strongest AI model scored 56% across the benchmark, which includes 25 target programs spanning various computing areas.
Verified 2026-09-09
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Rebuilding software from how it behaves is long, hard work, and AI is improving at it quickly.
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