PTENES
MODULE 3.6 · Track 3 · Model, cost, and orchestration

🗺️ Orchestration patterns

Not every problem is the same. Knowing how to choose the right topology — independent parallelism, pipeline, or fan-out — determines whether the system will be fast and cheap or slow and expensive. This module is the decision map.

7
Topics
~30
Minutes
Medium
Level
Standards
Type

Three patterns cover 90% of real-world cases: independent parallel work (all at once, with no dependencies), pipeline (A hands off to B, who hands off to C) and fan-out (one launches many that converge on a result). Understand the differences between them — especially the hidden cost of agent teams — is what separates those who designs systems of someone who only uses subagents.

Independent Parallelism Pipeline Fan-out Maestro triggers sub-A sub-B sub-C sub-D with no dependencies on one another Agent A Agent B Agent C Output final A’s output becomes B’s input Maestro fan-out sub-1 sub-2 sub-3 sub-4 sub-5 ∑ all converge in a summary

↑ Three topologies: each has different use cases, costs, and latency.

Detailed content

1

⚡ Independent parallel tasks

The simplest pattern, and the most powerful when jobs don't depend on one another. You have N tasks that can run at the same time, each in its own subagent, and the conductor collects the results at the end. No subagent needs to wait for another—the total time is the slower, not the sum of all of them.

📐 The 10+ file rule

Practical rule of thumb: if the job requires reading 10 or more files — or review 10 or more chapters, PDFs, or any unit of work — you're probably looking at a parallelization candidate. Above this volume, the cost of sequencing exceeds the orchestration overhead.

10 files sequentially: ~40 min
# vs
10 files in parallel (one subagent per file): ~4 min
1

Maestro identifies N independent jobs

It checks: "Can each job run without knowing the results of the others?" If so, it’s a candidate.

2

Triggers all at once

Each subagent opens its own window. They all run simultaneously, with no queue.

3

Collects the reports

The conductor waits for everyone to finish and synthesizes the results. You only see the final result — clean.

What it is:

N jobs with no dependencies between them running at the same time, each in its own subagent.

Why learn:

It’s the pattern that delivers real speed gains — total time is determined by the slowest one, not the sum. Knowing when to apply it is this module’s core skill.

Key concepts:

independence · simultaneous launch · time of the slowest · the 10+ files rule.

2

🔗 Pipeline: A → B → C

When one agent’s result is the input for the next one, you have a pipeline. There’s no parallelism here — the flow is sequential by necessity. The benefit isn’t speed: it’s specialization. Each stage has an agent focused only on that, with its own tools and instructions. Research is different from drafting; drafting is different from reviewing.

✓ Use a pipeline when

  • ✓A’s output is B’s input (real dependency)
  • ✓Each step needs different tools
  • ✓The order matters (research → draft → review)
  • ✓You want to clearly separate responsibilities

✗ Don’t use a pipeline when

  • ✗The jobs are independent (latency waste)
  • ✗The dependency is false — you just want to serialize
  • ✗The task is simple enough for a single agent

📊 Canonical example: research → draft → review

Agent A → Research sources, extract raw data
Agent B → Receives data from A, writes a draft
Agent C → Receives B's draft, reviews and approves it

Each agent can use Haiku, Sonnet, or Opus depending on the complexity of the step.

What it is:

A chain of agents where one agent’s output becomes the next agent’s input. Sequential due to dependencies.

Why learn:

Specializing by step beats using a single generalist agent. Separating responsibilities reduces errors and makes fine-tuning easier.

Key concepts:

real dependency · specialization by step · pipeline ≠ parallel · order matters.

3

📡 Fan-out: one dispatches many, one collects

Fan-out is parallelism with explicit convergence: the conductor launches N subagents and then synthesizes their reports into a single result. This is the “5 personas demo” pattern—each subagent uses a different lens, but they all report back to the same conductor, who assembles the final view.

🎯 What sets fan-out apart from pure parallelism

Pure parallelism

Different jobs that don't need to be combined. E.g.: compile 15 modules.

Fan-out

Multiple perspectives on the same object, synthesized into a report. E.g.: 5 personas review the same book.

💡 Fan-out across 15 chapters

Need to review a 15-chapter book? Fan-out: 1 subagent per chapter, all running at the same time. The orchestrator collects 15 reports and produces the editorial summary. Without fan-out, you’d read 15 chapters in a row in the same context—exhausting it before chapter 10.

What it is:

A variation of parallel execution where the orchestrator explicitly converges the results of N subagents into a single output.

Why learn:

It’s the pattern for diversity of perspectives (multiple lenses, adversarial review, complete coverage). The final synthesis is what adds value.

Key concepts:

explicit convergence · multiple perspectives · final synthesis · fan-out ≠ uncoordinated parallelism.

4

💬 Subagent × Agent Teams — the hidden cost

Agent teams are when multiple agents talk to each other — each message from one agent to another costs tokens. A regular subagent doesn't talk: it receives a brief, works in isolation, and delivers a report. In agent teams, the conversation itself has a cost — and this cost can exceed the value delivered if it isn't controlled.

✓ Subagent (default)

  • ✓Receives a brief, works in isolation
  • ✓Cost: only the work done
  • ✓Predictable: 1 task → 1 cost
  • ✓Orchestrator context protected

⚠️ Agent Teams — caution

  • !Agents talk to each other: each turn = cost
  • !Cost can grow geometrically
  • !Hard to audit what was decided where
  • !Is the value worth it? Measure before adopting

⚠️ ~15× cost — not because of the agents, but because of the conversation

Well-executed multi-agent work costs ~15× more than single-agent work. Most of that cost isn't the agents' work—it's the coordination overhead: repeated briefing prompts, shared context, status messages. Use agent teams only when the result clearly justifies it. When in doubt, use regular subagents.

What it is:

The distinction between subagents that work in isolation (cheap) and agent teams where agents talk to each other (cost per turn).

Why learn:

The difference directly affects session cost. If misunderstood, it leads to sessions 10× more expensive without proportionally better results.

Key concepts:

conversation turn = cost · isolation vs. communication · ~15× overhead · measure before adopting.

5

🧱 The 10+ files rule and the context wall

There is a turning point where continuing in the same context becomes counterproductive. We call it context wall: the point at which the model starts losing earlier information, mixing data from different files, or getting confused by cross-references. The rule of thumb: when you cross the 10 files, consider splitting it up.

📏 Context wall signals

  • 1 The model “forgets” a file you mentioned 5 files ago.
  • 2 The response mixes names of different files.
  • 3 Response time increases without the work becoming more complex.
  • 4 The conductor's context bar passes 60% — a warning sign.

💡 Independent jobs by unit of work

Practical translation: “15 chapters of a book” = 15 independent jobs. “20 code files to audit” = 20 jobs. “8 sales reports to analyze” = 8 jobs. Each job becomes a subagent. The conductor never reads the files — only the subagents’ reports.

What it is:

The practical threshold (10+ files) where a single context starts to degrade and splitting into subagents becomes necessary.

Why learn:

Without this heuristic, you use subagents too late—after the context has already degraded. With it, you decide before the problem appears.

Key concepts:

context wall · the 10+ rule · jobs per unit · the conductor reads reports, not files.

6

📚 Independent jobs: the case of the 15 chapters

The 15-chapter example is the best practical illustration of the pattern. You have a book with 15 chapters and want to know: "where is the weakest argument?" Doing this in a single context means reading all 15 chapters in sequence — the model starts mixing up the first chapters with the last ones. With 15 subagents in parallel, each person reads a chapter and submits a 1-page report. The conductor reads 15 one-page reports and synthesizes them.

📖

1 subagent / chapter

15 windows open simultaneously. Each reads 1 chapter with full focus.

📊

15 one-page reports

Each subagent returns a concise assessment of its chapter.

🎯

Maestro synthesizes

Reads 15 pages (not 15 chapters) and identifies the weakest argument.

📊 What changes in the orchestrator’s context

No subagents

95%

Packed context, degraded reading

With 15 subagents

18%

Maestro is free to reason

What it is:

Concrete application of independent parallelization: 1 subagent per unit of work (chapter, file, report), all in parallel.

Why learn:

Shows the real-world benefit: the orchestrator receives 15 one-page summaries instead of processing 15 chapters directly. Higher quality and speed.

Key concepts:

1 sub per unit · report = distilled summary · conductor reads little · context protected.

7

🗺️ How to choose the right topology

There’s a sequence of three questions to find the right topology. Answer in order—the first “yes” determines the default. If none apply, a single agent is probably enough.

?

Are the jobs independent of each other?

If yes → Independent parallelism (or fan-out if you need to synthesize).

?

Is one job’s output the next job’s input?

If yes → Pipeline (chain A → B → C).

?

Would the agents need to talk to each other?

If yes → Agent Teams (extra cost). Only if the value justifies it. Otherwise, redesign as parallel work + synthesis.

💡 The golden rule

If you can divide the problem into parts that don't need to talk, use parallel processing. If the output of one part is the input to the next, use a pipeline. If the parts would need to debate, think carefully before using agent teams — and consider whether a well-instructed orchestrator would do the job for less.

What it is:

The 3-question framework for choosing between parallel, pipeline, fan-out, or agent teams.

Why learn:

Knowing how to choose the right topology is the difference between an elegant, inexpensive system and a slow, expensive one. It’s the core design skill in Track 3.

Key concepts:

independence → parallel · dependency → pipeline · conversation → agent teams (added cost) · well-instructed orchestrator as an alternative.

📋

Real example: default table → use case

The table below maps the four patterns to concrete use cases. Use it as a quick reference when designing a system. For each case, the “Why?” column gives the deciding argument.

Standard Use case Why? Relative cost
Parallel Audit 20 code files Independent files, with no dependencies between them Low ✓
Pipeline Research → draft → article review The output of each step becomes the input for the next Medium
Fan-out 5 personas review the same book Multiple perspectives, explicit convergence Medium
Fan-out 15 chapters analyzed in parallel Each chapter stands alone, with a summary at the end Medium
Agent Teams Negotiation among specialist agents Agents need to exchange information with each other High ⚠️
Single agent Answer 1 question about 1 file Orchestration overhead isn’t justified Minimum ✓
typical orchestration agent (.md) example frontmatter
---
name: chapter-auditor
description: Revisa um único capítulo de texto em busca
  de argumentos fracos, inconsistências e lacunas.
  Use quando o maestro precisar auditar um capítulo
  isolado (padrão fan-out de N capítulos).
tools: Read                 # só lê o arquivo do capítulo
model: haiku               # rápido e barato por capítulo
---

You are a critical editor. You receive ONE chapter.
Identify: weakest argument, factual gaps, unclear sections.
Return a structured report: 3 bullets max. Be blunt.
⌨️

Ready-made prompts (copy and paste)

Three prompts to help you identify and use topologies in practice. The pattern: describe the problem, point out the dependency (or lack of one), and ask for the right topology.

Prompt 1 — which topology should I use to review 20 files? topology diagnosis
Tenho 20 arquivos de código para auditar. Cada um é
independente dos outros. Qual topologia de subagentes
devo usar? Justifique e mostre como estruturar o briefing
do maestro para disparar todos em paralelo.
Prompt 2 — fan out 15 chapters and synthesize fan-out applied
Use fan-out: dispare 1 subagente por capítulo para revisar
os 15 capítulos em paralelo. Cada sub deve retornar um
relatório de no máximo 3 bullets: argumento mais fraco,
lacuna factual, seção confusa. Sintetize no final.
Prompt 3 — research → draft → review pipeline sequential pipeline
Monte um pipeline de 3 agentes para criar um artigo:
Agente A: pesquisa e extrai 10 fontes sobre [tema].
Agente B: recebe as fontes de A e escreve o rascunho.
Agente C: recebe o rascunho de B e revisa para publicação.
Use Haiku em A, Sonnet em B e C.
🖥️

Simulated screen: fan-out across 5 chapters

Here's the terminal with a fan-out of 5 chapters underway. The conductor launched 5 subagents at the same time; each one reads 1 chapter with Haiku. Note: the conductor's context is at 9% — all the heavy reading happens in the subagents' windows.

claude code · auditar-livro · fan-out 5 chapters ⏱ 01:12
● cap-1 (intro) Haiku
42k tok
● cap-2 (theory) Haiku
58k tok
● cap-3 (examples) Haiku
71k tok
● cap-4 (advanced) Haiku
63k tok
● cap-5 (conclusion) Haiku
39k tok
fan-out active · synthesis waiting for 5 reports · default: 3 bullets/chapter
orchestrator · Sonnet
your context
9%

↑ Illustrative recreation of the terminal. 5 chapters in parallel with Haiku; orchestrator in Sonnet, context almost untouched.

🎯

Exercise

Three problems below. For each one, choose the right topology (parallel, pipeline, fan-out, or single agent) and justify in one sentence why you ruled out the others.

Problem 1

You have 30 monthly sales reports from different branches. You want to identify which branch had the largest drop in margin over the last 3 months. Each report is an independent PDF of ~20 pages.

Problem 2

You want to create a high-quality blog post about a technical topic. The natural workflow is: first research reliable sources, then write a draft based on those sources, then review the final draft.

Problem 3

You created a landing page and want feedback from 4 different perspectives: conversion (copywriter), SEO (search specialist), accessibility (WCAG auditor), and design (UX designer).

✅ Verification criteria

  • →Problem 1: Fan-out (30 independent PDFs → 30 subagents → synthesis). Pure parallelism if they didn't need to converge.
  • →Problem 2: Pipeline (research → draft → review are real dependencies; each stage's output feeds the next).
  • →Problem 3: Fan-out (4 independent perspectives on the same object → convergence into a feedback report).

If you justified why you did NOT use agent teams in all three cases, you got it exactly right.

Solved example — Problem 1

Topology: Fan-out. Why? 30 independent PDFs — each subagent reads 1 PDF and returns "branch X, down Y% in month Z". The conductor collects 30 lines and identifies the biggest drop. I ruled out the pipeline because there is no dependency between the PDFs. I ruled out agent teams because the agents don't need to exchange information with each other.

✅ Module summary

✓
Independent parallelism — N jobs with no dependencies between them; total time = the slowest one. Rule: 10+ files/units.
✓
Pipeline — A → B → C when one’s output is the next one’s input. Specialization at each stage.
✓
Fan-out — Parallel work with explicit convergence. Multiple perspectives → one synthesis. E.g., 15 chapters.
✓
Subagent × Agent Teams — Agent teams cost more because conversation has a cost. Use them only when the value justifies it.
✓
Context wall — Above 10+ files, splitting the work among subagents is necessary to maintain quality.
✓
Choose the topology — 3 questions: Are they independent? → parallel. Is there a dependency? → pipeline. Do they need to talk? → agent teams (extra cost).

End of Track 3 — next step:

Track 4 — Advanced & cross-environment: multi-agent architecture at scale, comparing models by role, security, and subagents in Codex.