> ## Documentation Index
> Fetch the complete documentation index at: https://docs.definable.ai/llms.txt
> Use this file to discover all available pages before exploring further.

# Nested Workflows

> Compose parallel, conditional, and sequential steps into a complex pipeline.

Build a workflow that combines parallel research, sequential writing, and a conditional quality gate.

<Steps>
  <Step title="Create the workflow">
    ```python nested_workflow.py theme={null}
    import asyncio
    from definable.agent import Agent
    from definable.agent.workflow import Workflow, Step, Parallel, Condition, Loop

    web_researcher = Agent(model="gpt-4o", instructions="Research the web for current information.")
    paper_reader = Agent(model="gpt-4o", instructions="Find and summarize academic papers.")
    writer = Agent(model="gpt-4o", instructions="Write a comprehensive article from research.")
    reviewer = Agent(model="gpt-4o", instructions="Review for accuracy. End with APPROVED or NEEDS_REVISION.")
    publisher = Agent(model="gpt-4o", instructions="Format the approved article for publication.")

    workflow = Workflow(
        name="full-pipeline",
        steps=[
            # Step 1: Research in parallel
            Parallel(name="research", steps=[
                Step(name="web", agent=web_researcher),
                Step(name="papers", agent=paper_reader),
            ]),
            # Step 2: Write article
            Step(name="write", agent=writer),
            # Step 3: Review and revise
            Loop(
                name="review-loop",
                steps=[
                    Step(name="review", agent=reviewer),
                    Condition(
                        name="quality-gate",
                        condition=lambda ctx: "APPROVED" in (ctx.get_last_step_content() or ""),
                        true_steps=Step(name="publish", agent=publisher),
                        false_steps=Step(name="rewrite", agent=writer),
                    ),
                ],
                end_condition=lambda outputs: any("APPROVED" in (o.content or "") for o in outputs),
                max_iterations=3,
            ),
        ],
    )

    async def main():
        result = await workflow.arun("Write about breakthroughs in quantum computing in 2026")
        print(result.content)

    asyncio.run(main())
    ```
  </Step>

  <Step title="Install and run">
    <Snippet file="install-definable.mdx" />

    ```bash theme={null}
    python nested_workflow.py
    ```
  </Step>
</Steps>