Multi-Agent Systems

Build teams of specialized agents that collaborate and delegate tasks to each other.

Why Multi-Agent?

Complex tasks benefit from specialization. Instead of one monolithic agent trying to do everything, you can create a team of focused agents:

• A coordinator that understands the overall goal and delegates
• A developer that writes code with filesystem and shell access
• A reviewer that checks code quality
• A researcher that searches the web for information

Each agent has its own model, tools, and instructions — optimized for its specific role.

Two Patterns: Delegation vs. Handoffs

Docker Agent supports two multi-agent patterns:

You can combine both patterns in the same configuration — an agent can have both sub_agents and handoffs.

Delegation with sub_agents

Agents delegate tasks using the built-in transfer_task tool, which is automatically available to any agent with sub_agents. The parent agent sends a task to a child agent, waits for the result, and then continues.

1. User sends a message to the root agent
2. Root agent analyzes the request and decides which sub-agent should handle it
3. Root agent calls transfer_task with the target agent, task description, and expected output
4. Sub-agent processes the task in its own agentic loop using its tools
5. Results flow back to the root agent, which responds to the user

# The transfer_task tool call looks like:
transfer_task(
  agent="developer",
  task="Create a REST API endpoint for user authentication",
  expected_output="Working Go code with tests"
)

Handoffs Routing

Handoffs are a peer-to-peer routing pattern where agents hand off the entire conversation to another agent. Unlike delegation, there is no sub-session — the conversation stays in a single session and the active agent simply switches.

This pattern is ideal for:

• Pipeline workflows — data flows through a chain of specialized agents
• Conversational routing — a coordinator routes the user to the right specialist, who can route back when done
• Graph topologies — agents can form cycles (A → B → C → A), enabling iterative workflows

How It Works

1. User sends a message to the starting agent
2. Agent A processes the message, then calls handoff to route to Agent B
3. Agent B becomes the active agent and sees the full conversation history
4. Agent B can respond, use its own tools, or hand off to another agent
5. This continues until an agent responds directly without handing off

# The handoff tool call looks like:
handoff(
  agent="summarizer"
)

Example

A coordinator routes to a researcher, who hands off to a summarizer, who returns to the coordinator:

Root ──→ Researcher ──→ Summarizer ──→ Root

agents:
  root:
    model: anthropic/claude-sonnet-4-5
    description: Coordinator that routes queries
    instruction: |
      Route research queries to the researcher.
    handoffs:
      - researcher

  researcher:
    model: openai/gpt-5-mini
    description: Web researcher
    instruction: |
      Search the web, then hand off to the summarizer.
    toolsets:
      - type: mcp
        ref: docker:duckduckgo
    handoffs:
      - summarizer

  summarizer:
    model: openai/gpt-5-mini
    description: Summarizes findings
    instruction: |
      Summarize the research results, then hand off
      back to root.
    handoffs:
      - root

Parallel Delegation with Background Agents

transfer_task is sequential — the coordinator waits for the sub-agent to finish before continuing. When you need to fan out work to multiple agents at the same time, use the background_agents toolset instead.

Add it to your coordinator’s toolsets:

agents:
  root:
    model: anthropic/claude-sonnet-4-5
    description: Research coordinator
    sub_agents: [researcher, analyst, writer]
    toolsets:
      - type: think
      - type: background_agents

The coordinator can then:

1. Dispatch several tasks at once with run_background_agent — each returns a task ID immediately
2. Monitor progress with list_background_agents or view_background_agent
3. Collect results once tasks complete
4. Cancel tasks that are no longer needed with stop_background_agent

# Start two tasks in parallel
run_background_agent(agent="researcher", task="Find recent papers on LLM agents")
run_background_agent(agent="analyst", task="Analyze our current architecture")

# Check on all tasks
list_background_agents()

# Read results when ready
view_background_agent(task_id="agent_task_abc123")

External Sub-Agents from Registries

Sub-agents don’t have to be defined locally — you can reference agents from OCI registries (such as the Docker Agent Catalog) directly in your sub_agents list. This lets you compose teams using pre-built, shared agents without duplicating their configuration.

agents:
  root:
    model: openai/gpt-5-mini
    description: Coordinator that delegates to local and catalog sub-agents
    instruction: |
      Delegate tasks to the most appropriate sub-agent.
    sub_agents:
      - local_helper
      - agentcatalog/pirate # pulled from registry automatically

  local_helper:
    model: openai/gpt-5-mini
    description: A local helper agent for simple tasks
    instruction: You are a helpful assistant.

External sub-agents are automatically named after their last path segment — for example, agentcatalog/pirate becomes pirate. You can also give them an explicit name using the name:reference syntax:

    sub_agents:
      - my_pirate:agentcatalog/pirate  # available as "my_pirate"
      - reviewer:docker.io/myorg/review-agent:latest

Harness-Backed Sub-Agents

Sub-agents can be backed by external coding CLIs — Claude Code, Codex, opencode, or pi — instead of a model API. Add a harness: block in place of a model: field to create a harness sub-agent:

agents:
  root:
    model: anthropic/claude-sonnet-4-5
    description: Orchestrator that plans and delegates
    instruction: |
      Break down coding tasks and delegate to the coding agents.
    sub_agents:
      - claude-coder
      - codex-coder

  claude-coder:
    description: Claude Code specialist
    harness:
      type: claude-code
      effort: high

  codex-coder:
    description: Codex specialist
    harness:
      type: codex

The orchestrator uses transfer_task to send work to a harness sub-agent just like any other sub-agent. Docker Agent handles the orchestration and hooks; the external CLI drives the coding loop.

Example: Development Team

agents:
  root:
    model: anthropic/claude-sonnet-4-5
    description: Technical lead coordinating development
    instruction: |
      You are a technical lead managing a development team.
      Analyze requests and delegate to the right specialist.
      Ensure quality by reviewing results before responding.
    sub_agents: [developer, reviewer, tester]
    toolsets:
      - type: think

  developer:
    model: anthropic/claude-sonnet-4-5
    description: Expert software developer
    instruction: |
      You are an expert developer. Write clean, efficient code
      and follow best practices.
    toolsets:
      - type: filesystem
      - type: shell
      - type: think

  reviewer:
    model: openai/gpt-5-mini
    description: Code review specialist
    instruction: |
      You review code for quality, security, and maintainability.
      Provide actionable feedback.
    toolsets:
      - type: filesystem

  tester:
    model: openai/gpt-5-mini
    description: Quality assurance engineer
    instruction: |
      You write tests and ensure software quality. Run tests
      and report results.
    toolsets:
      - type: shell
      - type: todo

Example: Research Team

agents:
  root:
    model: anthropic/claude-sonnet-4-5
    description: Research coordinator
    instruction: |
      Coordinate research tasks. Delegate web searches to
      the researcher and writing to the writer.
    sub_agents: [researcher, writer]
    toolsets:
      - type: think

  researcher:
    model: openai/gpt-5-mini
    description: Web researcher
    instruction: Search the web and gather information.
    toolsets:
      - type: mcp
        ref: docker:duckduckgo
      - type: memory
        path: ./research.db

  writer:
    model: anthropic/claude-sonnet-4-5
    description: Content writer
    instruction: Write clear, well-structured content.
    toolsets:
      - type: filesystem

Multi-Model Teams

A key advantage of multi-agent systems is using different models for different roles — picking the best model for each job:

models:
  fast:
    provider: openai
    model: gpt-5-mini
    temperature: 0.2 # precise

  creative:
    provider: openai
    model: gpt-5
    temperature: 0.8 # creative

  local:
    provider: dmr
    model: ai/qwen3 # runs locally, no API cost

agents:
  analyst:
    model: fast # cheap and fast for analysis
  writer:
    model: creative # creative for content
  helper:
    model: local # free for simple tasks

Shared Tools

Tools like todo can be shared between agents for collaborative task tracking:

toolsets:
  - type: todo
    shared: true # all agents see the same todo list

Best Practices

• Keep agents focused — Each agent should have a clear, narrow role
• Write clear descriptions — The coordinator uses descriptions to decide who to delegate to
• Give minimal tools — Only give each agent the tools it needs for its specific role
• Use the think tool when needed — For models without native reasoning, give coordinators the think tool so they reason about delegation. Models with built-in thinking (e.g., via thinking_budget) don’t need it
• Use the right model — Use capable models for complex reasoning, cheap models for simple tasks
• Choose the right pattern — Use sub_agents for hierarchical task delegation, handoffs for pipeline workflows and conversational routing