{"type":"post","stable_id":"post:mirrorcode-program-reconstruction-benchmark","slug":"mirrorcode-program-reconstruction-benchmark","title":"MirrorCode Tests Whether An Agent Can Rebuild A Whole Program From Behavior","description":"MirrorCode asks an agent to reimplement complete programs without source access and judges exact behavior on held-out end-to-end tests over long autonomous runs.","retrieval_nugget":"The benchmark covers 25 target programs, gives large time and token budgets, isolates agents from the internet and source code, and keeps private tests. Contamination from open-source pretraining remains an explicit caveat.","published_at":"2026-08-04","updated_at":"2026-08-06","record_date":"2026-08-04","date_kind":"published_at","topics":["coding-agents","benchmarks","long-horizon","software-reconstruction","evals"],"entities":["Epoch AI","METR","MirrorCode"],"source_urls":["https://epoch.ai/MirrorCode","https://arxiv.org/abs/2606.30182"],"source_format":"article","editorial_timing":{"lane":"regular_hourly","scheduled_at":"2026-08-07T10:00:00+03:00","real_news_delta":"owner-approved primary-source mechanism or merged analysis"},"visual_decision":{"status":"included","reason":"the central mechanism is a flow, loop, architecture, decision, or state transition that benefits from a diagram","reviewed_by":"codex"},"schema_version":"newruntime-agent-readable-v0.2","status":"published","visuals":[{"role":"hero","src":"/images/drip/mirrorcode-program-reconstruction-benchmark/mirrorcode-program-reconstruction-benchmark.webp","alt":"A whiteboard flow showing behavioral examples entering a sandboxed coding agent, a whole program emerging, and held-out end-to-end tests verifying it.","caption":"New Runtime synthesis from MirrorCode: What's the largest software project AI can complete on its own?."}],"routes":{"html":"https://newruntime.com/posts/mirrorcode-program-reconstruction-benchmark/","markdown":"https://newruntime.com/posts/mirrorcode-program-reconstruction-benchmark.md","json":"https://newruntime.com/posts/mirrorcode-program-reconstruction-benchmark.json"}}