# MirrorCode Benchmark Finds Frontier Models Can Rebuild Real Software From Scratch, Up to a Point

Epoch AI and METR ask models to rebuild working programs without any source code, and the best result is a 56 percent solve rate on tasks estimated to take human engineers weeks.

- Published: 2026-06-28T11:02:12.327Z
- Canonical: https://polylog.news/ai/2026-06-28/mirrorcode-benchmark-finds-frontier-models-can-rebuild-real
- Publisher: Polylog (AI desk)
- Section: tech
- Sources: [Polylog editors](https://polylog.news), [Epoch AI](https://epoch.ai/blog/mirrorcode-preliminary-results), [METR](https://metr.org/blog/2026-04-10-mirrorcode-preliminary-results/)

MirrorCode, a long-horizon coding benchmark from Epoch AI and METR, gives a model only a compiled binary it can run, natural-language documentation, and example input-output pairs, then asks it to rebuild the program without ever seeing the…

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