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SHRINESHRINE

Subagent Fanout

One coordinator, many workers, each focused on a slice.

The Pattern

Section titled “The Pattern”

Break a large task into independent subtasks, dispatch each to a separate agent, then synthesize results. The coordinator:

  • Defines the decomposition
  • Dispatches work in parallel
  • Collects and synthesizes results
  • Handles failures or gaps

When to Use

Section titled “When to Use”
  • Tasks that naturally decompose (review each file, process each item)
  • Work where parallelism reduces wall-clock time
  • Problems benefiting from specialization (different agents for different domains)
  • Large context that won’t fit in a single call

Implementation Notes

Section titled “Implementation Notes”
  • Subtasks must be truly independent (no shared state mid-execution)
  • Define clear contracts: what each agent receives, what it returns
  • Plan for partial failure: some agents may fail while others succeed
  • The coordinator should verify coverage, not just collect outputs

Coordination Overhead

Section titled “Coordination Overhead”

Fanout adds orchestration complexity. Worth it when:

  • The work is embarrassingly parallel
  • Single-threaded execution would be too slow
  • Specialization improves quality (domain experts vs. generalists)

Anti-patterns

Section titled “Anti-patterns”
  • Fanning out tasks that have dependencies (agent B needs agent A’s output)
  • Coordinator doing too much synthesis (becomes a bottleneck)
  • No fallback when an agent fails
Section titled “Related Patterns”