Vals AI: coding agent teams cost up to 5.1x more and mostly score the same
AnalysisOne of four comparisons came out statistically significant. Vals AI, a model-testing company, ran GPT-6 Sol and Claude Opus 5.5 through its Vibe Code Bench (50 full-stack web apps graded by UI tests) as single agents and as agent teams, publishing the results on October 9. Teams cost 1.8 to 5.1 times as much. Only GPT-6 Sol at medium effort gained, by 7.3 points. Opus at maximum effort rose from 89.8% to 93.2% while its average bill per app climbed from $23.77 to $122, a gain the statistics could not separate from noise. Turning up a single agent's reasoning effort did more for Sol than giving it coworkers.