Version 1.0 · CC BY 4.0 · 22 May 2026 · 10.xxxx/ctm.ar.2026.0006
Technical report documenting how 112 agent papers report variance, compute, prompts and judging procedures, with the full coding sheet. Supports the survey “A Survey of Evaluation Practices for Language-Model Agents”.
Version 2 · 3 reviewer reports · 14 August 2026 · 10.xxxx/ctm.pb.2026.0008
Most agent benchmarks report one run per task, yet agents are stochastic. We analyse run-to-run variance on four public agent benchmarks and derive the number of repeated runs needed to detect a given difference between two systems at conventional power. For differences smaller than five points, single-run comparisons have less than 40% power on all four benchmarks. We provide a sequential testing procedure that stops early when the evidence is clear, and show that it halves the cost of repeated evaluation while keeping the false-positive rate below 5%.