BIG-Bench Hard (BBH)

BIG-Bench Hard is a curated subset of 23 challenging tasks from BIG-Bench that require multi-step reasoning, where chain-of-thought prompting significantly helps performance. Tasks include algorithmic reasoning, logical deduction, causal judgment, and more. By 2024–2025, frontier models were approaching saturation (>90%) on BBH, prompting the creation of the harder BBEH variant.