Study: AI agent teams cost up to 5.1x more for little gain

Vals AI found teams of AI agents barely beat solo agents while costing up to 5.1x more. Only one of four tests with GPT-6 Sol and Claude Opus 5.5 showed a measurable gain. Anthropic's own data reportedly shows quality plateauing beyond ten agents while token costs keep rising.

Why it matters: This cuts against the push toward large parallel sub-agent setups, such as Claude Managed Agents now supporting up to 1,000 sub-agents. Cheaper tokens were already raising demand, so wasteful multi-agent designs risk eating those savings. Builders should benchmark against a single strong agent before scaling out.