Why Single Agents Beat Multi-Agent Systems at Equal Token Budgets

TL;DR Stanford (Tran & Kiela, arXiv 2604.02460) tested single-agent vs multi-agent systems with identical thinking-token budgets Single agent wins on accuracy AND on compute, across three model families The mechanism is information theory — every handoff loses information (Data Processing Inequality) The Gemini 2.5 API has token-budget enforcement artifacts that biased a year of prior benchmarks The hidden variable nobody controls for When you compare a single-agent LLM to a multi-agent orch