When to Delegate: A Measurement Study of Bounded Agent Teams for Personal Super Agents

Personal super agents coordinate many tools while remaining fast, safe, and accountable to one user. A popular design is a Router delegating to Workers. Recent work shows coordination can cost more than it returns, but transfer to personal agents—single-user context, side-effecting tools, cross-turn references, and refusals—is not established. We present the bounded-delegation runtime protocol, instantiate it in Eva, a 22-tool in-vehicle agent, and introduce Eva-Bench, 80 rule-scored tasks in ten categories. With one real model and tool set, we compare monolithic ReAct, bounded team, and unbounded team, and ablate budgets, reasoning, concurrency, guards, ledger, and injected failures. Delegation is not free: the main team pays 2.75×the latency and 2.59×the tokens. In one full-suite run it leads by one task (92.5% versus 91.2%), but three full-suite repetitions give 92.9% versus 93.3% (difference -0.4pp). Four post hoc temperature- matched runs average 90.6% (range 86.2–93.8%), so temperature alone does not explain the team’s small, unstable lead. We do not claim a general team advantage. The stable finding is the tax; service workflows and cross-turn references favor the team in repeated data, while safety and aggregate success do not. Bounded budgets reduce tail latency, reasoning is a net cost, and guards/ledger are null at oracle success. A selective-delegation policy reaches 95.0% at 6.27s in one run, versus 91.2% at 3.22s monolithic and 92.5% at 8.85s for the fixed team; it is exploratory. Delegation should be earned by request structure, and evaluation must report organizational overhead separately from task success.