Fan-out

What is a Fan-out

Fan-out is the pattern of splitting one large task into several independent pieces and dispatching a separate agent to handle each piece, then collecting every result back into a single combined output. Auditing fifty files for a specific issue is a natural fan-out candidate: fifty independent lookups, one agent per file or per batch, results merged into one report at the end.

The pattern only works cleanly when the split pieces are genuinely independent. If dispatching agent B actually needs to know what agent A found, the two are not truly parallelizable, and fanning them out just adds coordination overhead without the speed benefit. The upfront judgment call, does this actually split, is the part that determines whether fan-out helps or just adds complexity.

Someone has to own the reassembly step, usually an orchestrator that dispatched the pieces in the first place. A fan-out with no clear owner for combining results tends to produce several separate answers instead of one coherent one, which defeats the purpose of splitting the task in the first place.