HumanLayer

SlopCodeBench update 10/2026 - Opus 5.5 update, Astra improves by 1.5% over gpt-5.5, xhigh considered harmful

Dex Horthy of HumanLayer reruns frontier coding models on the full SlopCodeBench (36 problems, 196 checkpoints), where agents must extend their own code across changing requirements. Strict pass rates ranged 12.2-16.3%, led by gpt-6 Astra, versus 14.8% for gpt-5.5 in May; xhigh effort cost 2-4x more than medium and sometimes scored worse.

Research · AI Coding Agents · Benchmarks · Large Language Models