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Claude Fable 5 Leads GPT-5.6 Sol by More Than 3× on MirrorCode
Solve rate on long-horizon software reimplementation tasks
Claude Fable 5 and GPT-5.6 Sol
20%
64%
Why it matters: Claude Fable 5 solved 64% of Epoch AI’s MirrorCode tasks, more than triple GPT-5.6 Sol’s 20% solve rate on a benchmark that requires agents to rebuild complete software projects.
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