choosing-swarm-patterns · git:20260610.2c174d7 · 2026-06-10 · sha256 820e2c71b19e9730
choosing-swarm-patterns git:20260610.2c174d7A
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---
name: choosing-swarm-patterns
description: Use when coordinating multiple AI agents with Agent Relay's workflow engine and need to pick the right orchestration pattern - covers the 10 core patterns (fan-out, pipeline, hub-spoke, consensus, mesh, handoff, cascade, dag, debate, hierarchical) plus 14 specialized ones, with decision framework and accurate workflow/YAML examples.
---
### Overview
The Agent Relay workflow engine (`@relayflows/core`) supports 24 swarm patterns via a single `swarm.pattern` field. Patterns are configured declaratively in YAML or programmatically via the `workflow()` fluent builder — there are no standalone `fanOut(...)` / `hubAndSpoke(...)` helpers. Pick the simplest pattern that solves the problem; add complexity only when the system proves it's insufficient.
### Two ways to run a pattern
#### **1. YAML (portable):**
```ts
import { runWorkflow } from '@relayflows/core';
const run = await runWorkflow('workflows/feature-dev.yaml', {
vars: { task: 'Add OAuth login' },
});
```
#### **2. Fluent builder (programmatic):**
```ts
import { workflow } from '@relayflows/core';
const run = await workflow('feature-dev')
.pattern('hub-spoke')
.channel('swarm-feature-dev')
.agent('lead', { cli: 'claude', role: 'lead' })
.agent('developer', { cli: 'codex', role: 'worker', interactive: false })
.step('plan', { agent: 'lead', task: 'Plan {{task}}' })
.step('implement', { agent: 'developer', task: 'Implement: {{steps.plan.output}}', dependsOn: ['plan'] })
.run();
```
Both paths hit the same `WorkflowRunner`.
### Quick Decision Framework
```
Is the task independent per agent?
YES → fan-out (parallel workers, hub collects)
Does each step need the previous step's output?
YES → Is it strictly linear?
YES → pipeline
NO → dag (parallel where possible, `dependsOn` edges)
Does a coordinator need to stay alive and adapt?
YES → hub-spoke (single-level hub + workers)
hierarchical (structurally identical in current impl; use for naming/intent)
Is the task about making a decision?
YES → Do agents need to argue opposing sides?
YES → debate (adversarial, full mesh)
NO → consensus (cooperative, full mesh + coordination.consensusStrategy)
Does the right specialist emerge during processing?
YES → handoff (sequential chain, one active at a time)
Do all agents need to freely collaborate?
YES → mesh (full peer-to-peer edges)
Is cost the primary concern?
YES → cascade (chain of increasingly capable agents; each step's prompt
decides whether to pass through or redo the prior output)
```
### Pattern Reference (Core 10)
| # | Pattern | Topology (actual edges) | Best For |
| --- | ---------------- | ------------------------------------------------------------------------------------------------------------------- | --------------------------------------------------------------------------- |
| 1 | **fan-out** | Hub broadcasts to N workers; workers reply to hub only | Independent subtasks (reviews, research, tests) |
| 2 | **pipeline** | Linear chain (agent*i → agent*{i+1}) | Ordered stages (design → implement → test) |
| 3 | **hub-spoke** | Hub ↔ spokes (bidirectional); no spoke-to-spoke | Dynamic coordination, lead reviews/adjusts |
| 4 | **consensus** | Full mesh; decision via `coordination.consensusStrategy` | Architecture decisions, approval gates |
| 5 | **mesh** | Full mesh (every agent ↔ every other) | Brainstorming, collaborative debugging |
| 6 | **handoff** | Chain; passes control forward | Triage, specialist routing |
| 7 | **cascade** | Chain of `dependsOn` steps; all run on success, downstream skipped on upstream failure (no built-in "fall through") | Cost optimization: cheap first, each step's prompt passes through or redoes |
| 8 | **dag** | Edges from step `dependsOn` | Mixed dependencies, parallel where possible |
| 9 | **debate** | Full mesh (same topology as mesh; roles drive behavior) | Rigorous adversarial examination |
| 10 | **hierarchical** | Hub + subordinates (single-level in current impl) | Large teams; semantic distinction from hub-spoke |
> **Heads up:** `hierarchical` resolves to the same edge structure as `hub-spoke` in `coordinator.ts:313-319`. Multi-level tree topology is not currently implemented — use pattern name for intent, but expect the same runtime graph.
### Additional Patterns (role-driven)
These 14 additional patterns exist in `SwarmPattern` (types.ts:114-139). The coordinator has role-based auto-selection heuristics (`coordinator.ts:51-165`), but they only fire when `swarm.pattern` is **omitted** — YAML validation requires it (`runner.ts:2105-2117`), so auto-selection is effectively a programmatic-API feature. In YAML, set `swarm.pattern` explicitly.
Topology is still resolved per-pattern once selected; the "Triggering roles" column reflects what the coordinator looks for to shape edges (per `coordinator.ts:250-450`):
| Pattern | Roles the topology keys off | Topology |
| ----------------- | ------------------------------------------------------- | ---------------------------------------------- |
| `map-reduce` | `mapper` + `reducer` | coordinator → mappers → reducers → coordinator |
| `scatter-gather` | — | hub → workers → hub |
| `supervisor` | `supervisor` | supervisor ↔ workers |
| `reflection` | `critic` or `reviewer` (auto-select uses `critic` only) | producers → critic → producers (loop) |
| `red-team` | `attacker`/`red-team` + `defender`/`blue-team` | adversarial mesh with optional judges |
| `verifier` | `verifier` | producers → verifiers → back to producers |
| `auction` | `auctioneer` | auctioneer → bidders → auctioneer |
| `escalation` | `tier-*` | tiered chain, escalate up / report down |
| `saga` | `saga-orchestrator`, `compensate-handler` | orchestrator ↔ participants |
| `circuit-breaker` | `primary` + `fallback`/`backup` | try primary, fallback on failure |
| `blackboard` | `blackboard` / `shared-workspace` | shared state hub |
| `swarm` | `hive-mind` / `swarm-agent` | stigmergy-style |
| `competitive` | — (declared explicitly) | independent parallel implementations + judge |
| `review-loop` | `implement*` + 2+ `reviewer*` | implementer ↔ reviewers |
### Structured Squad Review Loop
- Split the work into bounded implementation squads. Each squad owns a non-overlapping file or subsystem scope.
- Give each squad an implementer plus a shadow/review partner. The shadow follows the implementer in real time, checks alignment with the spec, and posts concise feedback before the work drifts.
- Require the implementer to self-reflect before external review: compare the final diff against the spec, AGENTS.md / CLAUDE.md, recent local conventions, tests, and declared non-goals.
- Run an independent self-review/fresh-eyes agent that reads the actual files and recent repo context, not just the chat transcript.
- Send that review back to the implementer for one repair round.
- After squads converge, run a final two-agent review team, usually one Claude reviewer and one Codex reviewer, independently. They compare notes, merge findings, and produce one final verdict.
- Spawn fresh fix agents for final-review findings. Those fix agents self-reflect, then the final reviewers re-check the post-fix state until the spec is fully satisfied or a blocker is documented.
- Use `supervisor` or `hub-spoke` when a lead needs to coordinate live squads.
- Use `review-loop` when the main risk is code quality and feedback iteration.
- Use `reflection` when critic feedback should loop directly back to producers.
- Use `verifier` when completion evidence matters more than design debate.
- Use `competitive` only when independent alternative implementations are useful; otherwise split by ownership scope.
### Pattern Details
#### 1. fan-out — Parallel Workers
```ts
await workflow('review')
.pattern('fan-out')
.agent('lead', { cli: 'claude', role: 'lead' })
.agent('auth-rev', { cli: 'claude', role: 'worker', interactive: false })
.agent('db-rev', { cli: 'claude', role: 'worker', interactive: false })
.step('review-auth', { agent: 'auth-rev', task: 'Review auth.ts' })
.step('review-db', { agent: 'db-rev', task: 'Review db.ts' })
.run();
```
#### 2. pipeline — Sequential Stages
```yaml
swarm: { pattern: pipeline }
agents:
- { name: designer, cli: claude }
- { name: implementer, cli: codex, interactive: false }
- { name: tester, cli: codex, interactive: false }
workflows:
- name: build
steps:
- {
name: design,
agent: designer,
task: 'Design the API schema',
verification: { type: output_contains, value: DONE },
}
- {
name: implement,
agent: implementer,
dependsOn: [design],
task: 'Implement: {{steps.design.output}}',
}
- { name: test, agent: tester, dependsOn: [implement], task: 'Write integration tests' }
```
#### 3. hub-spoke — Persistent Coordinator
```ts
await workflow('api-build')
.pattern('hub-spoke')
.channel('swarm-api')
.agent('lead', { cli: 'claude', role: 'lead' })
.agent('db-worker', { cli: 'claude', role: 'worker' }) // interactive by default — hub DMs it
.agent('api-worker', { cli: 'claude', role: 'worker' }) // interactive by default — hub DMs it
.step('models', { agent: 'db-worker', task: 'Build database models' })
.step('routes', { agent: 'api-worker', task: 'Build route handlers', dependsOn: ['models'] })
.step('review', { agent: 'lead', task: 'Review everything', dependsOn: ['routes'] })
.run();
```
#### 4. consensus — Cooperative Voting
```yaml
swarm: { pattern: consensus }
agents:
- { name: perf, cli: claude, role: reviewer }
- { name: dx, cli: claude, role: reviewer }
- { name: sec, cli: claude, role: reviewer }
coordination:
consensusStrategy: majority # declarative marker: majority | unanimous | quorum
votingThreshold: 0.66
workflows:
- name: decide
steps:
- { name: evaluate-perf, agent: perf, task: 'Evaluate perf of Fastify migration' }
- { name: evaluate-dx, agent: dx, task: 'Evaluate DX of Fastify migration' }
- { name: evaluate-sec, agent: sec, task: 'Evaluate security of Fastify migration' }
```
#### 5. mesh — Peer Collaboration
```ts
await workflow('debug-auth')
.pattern('mesh')
.channel('swarm-debug')
.agent('logs', { cli: 'claude' })
.agent('code', { cli: 'claude' })
.agent('repro', { cli: 'claude' })
.step('logs', { agent: 'logs', task: 'Check server logs' })
.step('code', { agent: 'code', task: 'Review auth code' })
.step('repro', { agent: 'repro', task: 'Write repro test' })
.run();
```
#### 6. handoff — Dynamic Routing
```yaml
swarm: { pattern: handoff }
agents:
- { name: triage, cli: claude }
- { name: billing, cli: claude }
- { name: tech, cli: claude }
workflows:
- name: support
steps:
- { name: triage, agent: triage, task: 'Triage: {{request}}' }
- { name: billing, agent: billing, dependsOn: [triage], task: 'Handle billing' }
- { name: tech, agent: tech, dependsOn: [triage], task: 'Handle tech issues' }
```
#### 7. cascade — Cost-Aware Fallthrough
```ts
await workflow('answer')
.pattern('cascade')
.agent('haiku', { cli: 'claude', model: 'claude-haiku-4-5-20251001' })
.agent('sonnet', { cli: 'claude', model: 'claude-sonnet-4-6' })
.agent('opus', { cli: 'claude', model: 'claude-opus-4-7' })
.step('try-haiku', { agent: 'haiku', task: '{{question}}' })
.step('try-sonnet', {
agent: 'sonnet',
task: 'If this is a complete answer, echo it verbatim. Otherwise answer anew:\n{{steps.try-haiku.output}}',
dependsOn: ['try-haiku'],
})
.step('try-opus', {
agent: 'opus',
task: 'Final-tier answer, using prior attempts for context:\n{{steps.try-sonnet.output}}',
dependsOn: ['try-sonnet'],
})
.run();
```
#### 8. dag — Directed Acyclic Graph
```ts
await workflow('fullstack')
.pattern('dag')
.maxConcurrency(3)
.agent('dev', { cli: 'codex', role: 'worker' })
.step('scaffold', { agent: 'dev', task: 'Create project scaffold' })
.step('frontend', { agent: 'dev', task: 'Build React UI', dependsOn: ['scaffold'] })
.step('backend', { agent: 'dev', task: 'Build API', dependsOn: ['scaffold'] })
.step('integrate', { agent: 'dev', task: 'Wire together', dependsOn: ['frontend', 'backend'] })
.run();
```
#### 9. debate — Adversarial Refinement
```yaml
swarm: { pattern: debate }
agents:
- { name: pro, cli: claude, role: debater, task: 'Argue FOR monorepo' }
- { name: con, cli: claude, role: debater, task: 'Argue FOR polyrepo' }
- { name: judge, cli: claude, role: judge, task: 'Decide after 3 rounds' }
coordination:
barriers:
- { name: debate-done, waitFor: [pro-round-3, con-round-3] }
```
#### 10. hierarchical — Multi-Level (structurally hub-spoke today)
```ts
await workflow('large-team')
.pattern('hierarchical')
.agent('lead', { cli: 'claude', role: 'lead' })
.agent('fe-coord', { cli: 'claude', role: 'coordinator' })
.agent('be-coord', { cli: 'claude', role: 'coordinator' })
.agent('fe-dev', { cli: 'codex', role: 'worker', interactive: false })
.agent('be-dev', { cli: 'codex', role: 'worker', interactive: false })
.step('plan', { agent: 'lead', task: 'Coordinate full-stack app' })
.step('fe-plan', { agent: 'fe-coord', task: 'Manage frontend', dependsOn: ['plan'] })
.step('be-plan', { agent: 'be-coord', task: 'Manage backend', dependsOn: ['plan'] })
.step('fe-impl', { agent: 'fe-dev', task: 'Build components', dependsOn: ['fe-plan'] })
.step('be-impl', { agent: 'be-dev', task: 'Build API', dependsOn: ['be-plan'] })
.run();
```
### Verification & Completion Signals
#### An agent step can complete in several ways in the `@relayflows/core` runner:
```yaml
verification:
type: output_contains # or: exit_code | file_exists | custom
value: DONE # or: PLAN_COMPLETE, IMPLEMENTATION_COMPLETE, REVIEW_COMPLETE
```
### Agent Relay MCP - Correct Tool Names
The old category-expanded names are wrong. Current Agent Relay MCP tools are
flat names. In a client that decorates MCP tools, the prefix comes from the
configured server key; workflow prompts commonly show `mcp__relaycast__send_dm`,
while an `agent-relay` server key may expose `mcp__agent_relay__send_dm`.
| Purpose | Canonical tool | Common workflow-prefixed form |
| ------------------------ | ----------------- | --------------------------------- |
| Send DM to another agent | `send_dm` | `mcp__relaycast__send_dm` |
| Check inbox | `check_inbox` | `mcp__relaycast__check_inbox` |
| List agents | `list_agents` | `mcp__relaycast__list_agents` |
| Post to a channel | `post_message` | `mcp__relaycast__post_message` |
| Reply in a thread | `reply_to_thread` | `mcp__relaycast__reply_to_thread` |
| Spawn sub-agent | `add_agent` | `mcp__relaycast__add_agent` |
| Remove sub-agent | `remove_agent` | `mcp__relaycast__remove_agent` |
> `interactive: false` agents run as non-interactive subprocesses with no relay connection. They must not call Relay MCP tools.
### Reflection (Trajectories)
#### Reflection is **not** a `reflectionThreshold` callback. It's configured via the `trajectories:` block:
```yaml
trajectories:
enabled: true
reflectOnBarriers: true # config flag exists but runner does NOT currently invoke this path
reflectOnConverge: true # fires at parallel convergence points (runner.ts:2762-2779)
autoDecisions: true # record retry/skip/fail decisions
```
### Common Mistakes
| Mistake | Why It Fails | Fix |
| -------------------------------------------- | ----------------------------------------------------------------------------- | --------------------------------------------------------------------------------------------- |
| Using mesh/debate for everything | Full-mesh blows up message volume past ~5 agents | Use hub-spoke or dag for most tasks |
| Pipeline for independent work | Sequential bottleneck | Use fan-out or dag |
| Hub-spoke for 2 agents | Hub is unnecessary overhead | Use pipeline or fan-out |
| Expecting `consensusStrategy` to tally votes | Runner has no vote-tally logic; field only affects coordinator auto-selection | Aggregate votes in a judge/lead step that reads `{{steps.*.output}}` |
| Handoff with "routing = skip other branches" | Skipping only fires on upstream **failure**, not routing decisions | Emit a routing token in triage output; downstream prompts self-no-op if token doesn't match |
| Cascade expecting skip-on-success | Runner has no cascade skip logic; failed upstream skips downstream | Chain downstream prompts to pass-through or redo based on `{{steps.previous.output}}` |
| Relying on `reflectOnBarriers` | Config flag exists but runner never calls it | Use `reflectOnConverge` for convergence reflection; use `reflection` pattern for critic loops |
| `interactive: false` agent calling MCP | Non-interactive subprocess has no relay | Use `interactive: true` (default) or emit output on stdout |
| Relying on multi-level `hierarchical` | Topology is single-level hub in current impl | Use pattern for naming; model levels via `dependsOn` graph |
| Writing `mcp__relaycast__send(...)` | Wrong tool name | Use `post_message` / `mcp__relaycast__post_message` or `send_dm` / `mcp__relaycast__send_dm` |
### Resume & Re-run
#### ```ts
```ts
// Resume a failed run:
await runWorkflow('feature-dev.yaml', { resume: '<runId>' });
// Skip ahead, re-using cached outputs from an earlier run:
await runWorkflow('feature-dev.yaml', {
startFrom: 'review',
previousRunId: '<runId>',
});
```
### Complete YAML Example
#### ```yaml
```yaml
version: '1.0'
name: feature-dev
description: 'Blueprint-style feature development with quality gates.'
swarm:
pattern: hub-spoke
maxConcurrency: 2
timeoutMs: 3600000
channel: swarm-feature-dev
idleNudge: { nudgeAfterMs: 120000, escalateAfterMs: 120000, maxNudges: 1 }
agents:
- { name: lead, cli: claude, role: lead, permissions: { access: full } }
- { name: planner, cli: codex, role: planner, interactive: false, permissions: { access: readonly } }
- { name: developer, cli: codex, role: worker, interactive: false, permissions: { access: readwrite } }
- { name: reviewer, cli: claude, role: reviewer, permissions: { access: readonly } }
workflows:
- name: feature-delivery
onError: retry
preflight:
- { command: 'git status --porcelain', failIf: non-empty, description: 'Clean worktree' }
steps:
- name: plan
agent: planner
task: 'Plan: {{task}}'
verification: { type: output_contains, value: PLAN_COMPLETE }
- name: implement
agent: developer
dependsOn: [plan]
task: 'Implement: {{steps.plan.output}}'
verification: { type: output_contains, value: IMPLEMENTATION_COMPLETE }
- name: test
type: deterministic
dependsOn: [implement]
command: npm test
- name: review
agent: reviewer
dependsOn: [test]
task: 'Review implementation'
verification: { type: output_contains, value: REVIEW_COMPLETE }
coordination:
barriers:
- { name: delivery-ready, waitFor: [plan, implement, review], timeoutMs: 900000 }
trajectories:
enabled: true
reflectOnBarriers: true
reflectOnConverge: true
errorHandling:
strategy: retry
maxRetries: 2
retryDelayMs: 5000
```
### Source of Truth
| Claim | File |
| ----------------------------------------------------------------- | --------------------------------------------------------------------------------------- |
| Pattern enum (24 patterns) | `@relayflows/core/dist/schema.d.ts` (`SwarmPattern`) |
| Topology resolution per pattern | `@relayflows/core/dist/coordinator.js` |
| Interactive-only topology edges | `@relayflows/core/dist/coordinator.js` filters `interactive: false` agents |
| Pattern auto-selection heuristics | `@relayflows/core/dist/coordinator.js` |
| `WorkflowBuilder` fluent API | `@relayflows/core/dist/builder.d.ts` |
| `runWorkflow(yamlPath, options)` | `@relayflows/core/dist/run.d.ts` |
| YAML validation requires `version` + `name` + `swarm.pattern` | `@relayflows/core/dist/runner.js` |
| MCP tool names | `packages/cli/src/cli/agent-relay-mcp.ts`, `@relayflows/core/dist/channel-messenger.js` |
| Completion modes (verification / evidence / owner / process-exit) | `@relayflows/core/dist/runner.js`, `@relayflows/core/dist/step-executor.js` |
| Trajectory reflection | `@relayflows/core/dist/trajectory.js`, `@relayflows/core/dist/runner.js` |