In agentic systems, Fan-out is the process within a parallel execution pattern where a single task is split into multiple, independent subtasks that are executed concurrently. An orchestrator “fans out” these subtasks to different worker agents, processes, or tool calls, initiating simultaneous work on different parts of a problem.
The fundamental prerequisite for a successful fan-out is the true independence of the subtasks. Before fanning out, an orchestrator must verify that the parallel branches can run without interfering with one another. Key independence tests include checking if any branch must wait for another’s output, if they write to a shared state that could cause race conditions, or if the execution order affects the final outcome. If dependencies exist, the tasks are not truly independent, and a sequential or graph-based approach is more appropriate.
This pattern is powerful for improving speed and exploring diverse solutions. For example, a single research query can be fanned out to multiple agents, each using a different search engine or database. Similarly, multiple agents can be tasked with generating different creative solutions to the same problem. The complexity of the fan-out pattern lies not in the splitting of the task, but in the subsequent “fan-in” step, which must collect, synchronize, and merge the results.