Nested Selector

uv pip install -U "agno[openai]"
export OPENAI_API_KEY="your_openai_api_key"

from typing import List, Union

from agno.agent import Agent
from agno.models.openai import OpenAIChat
from agno.workflow.router import Router
from agno.workflow.step import Step
from agno.workflow.types import StepInput
from agno.workflow.workflow import Workflow

step_a = Agent(name="step_a", model=OpenAIChat(id="gpt-4o-mini"), instructions="Step A")
step_b = Agent(name="step_b", model=OpenAIChat(id="gpt-4o-mini"), instructions="Step B")
step_c = Agent(name="step_c", model=OpenAIChat(id="gpt-4o-mini"), instructions="Step C")


def nested_selector(step_input: StepInput, step_choices: list) -> Union[str, Step, List[Step]]:
    """
    When choices contains nested lists like [step_a, [step_b, step_c]],
    the nested list becomes a Steps container in step_choices.
    """
    user_input = step_input.input.lower()

    # step_choices[0] = Step for step_a
    # step_choices[1] = Steps container with [step_b, step_c]

    if "single" in user_input:
        return step_choices[0]  # Just step_a
    else:
        return step_choices[1]  # Steps container with step_b -> step_c


workflow = Workflow(
    name="Nested Choices Routing",
    steps=[
        Router(
            name="Nested Router",
            selector=nested_selector,
            choices=[step_a, [step_b, step_c]],  # Nested list becomes Steps container
        ),
    ],
)

if __name__ == "__main__":
    workflow.print_response("Run the sequence", stream=True)