Architecture Patterns

Patterns are coordination tools, not required ceremony. Pick one only when it makes ownership, sequencing, or review clearer than a direct workflow.

Pipeline

Best fit: sequential work where each phase consumes a stable prior artifact.

Shape: scope → research → build → review → validate.

Use it when order is the main risk. Do not use it when independent branches would be forced to wait for one another.

Fan-out/Fan-in

Best fit: several independent, read-heavy slices followed by synthesis.

Shape: one request → bounded parallel findings → one synthesis owner.

Give each branch a non-overlapping artifact or isolated environment. Do not use it when branches depend on shared mutable state.

Expert Pool

Best fit: a router selects one or more specialists from a stable set.

Shape: classify request → select specialist → return bounded result.

Use explicit routing criteria and one fallback for ambiguous requests. Do not use it when every request needs nearly every specialist.

Producer-Reviewer

Best fit: generated work benefits from a separate critique and bounded revision.

Shape: produce → review → fix or approve.

The reviewer reads the original request, the produced artifact, and the acceptance criteria. Cap revision loops so “review” cannot become an unbounded second production process.

Supervisor

Best fit: the backlog changes during execution and needs reprioritization.

Shape: assign → inspect status → reassign or integrate.

The supervisor owns the queue and final integration. Keep worker writes isolated and report partial failure explicitly.

Hierarchical Delegation

Best fit: a large goal separates naturally into shallow sub-goals, each with its own local workflow.

Shape: top-level goal → domain lead → bounded execution.

Keep the hierarchy to two coordination layers. Flatten it when routing starts to hide rather than clarify dependencies.

Combine patterns carefully

Common combinations include:

• Pipeline + Fan-out/Fan-in: ordered stages with a parallel evidence phase;
• Fan-out/Fan-in + Producer-Reviewer: parallel drafts followed by one review;
• Supervisor + Expert Pool: a changing queue routed to explicit specialists;
• Hierarchical Delegation + Pipeline: shallow domain splits with local order.

Document the outer pattern first and keep the inner variation local to the phase that needs it.

Quick selection table

Read the workflow guide for the phase contract and the output specifications for durable artifact shapes.