Hex built a suite of analytical evals to test data-analysis models and found Claude Fable 5 outperforms its Opus 4.x predecessors by 10–15%, nailing both semantically modeled and raw-data tasks with fewer mistakes. They’ve also designed a tougher “Frontier” benchmark for long-horizon, open-ended scenarios, where Fable 5’s careful assumptions and cross-checks boost its pass rate to around 58%.