GPQA.

GPQA narrows scope to PhD-level expert questions while raising verifiability — each answer is checked by domain-expert validators. MMLU-Pro raised the ceiling; GPQA shifted the task from breadth to verifiable expert depth.

HLE is the logical endpoint of the expert-difficulty trend: 2,500 questions where the bar is 'only a genuine domain expert can answer this reliably.' The current frontier attention path because no model has cleared 35%.